Florida Engineering and Indust
University of I
Bulletin No. 12
MOLD AND MILDEW CONTROL
FOR INDUSTRY AND THE HOME
S. S. BLOCK
Assistant Research Engineer
COLLEGE OF ENGINEERING
UNIVERSITY OF FLORIDA
TABLE OF CONTENTS
W hat is M old.................................................................................. 5
Mold Damage ........................................ .............. 6
Conditions for Mold Growth............... .................-...... 8
Methods of Mold Control.................................................--.... 9
Removal of Oxygen............................. ................ 9
Removal of Nutrients-Cleanliness........................ ...... 9
Temperature Control ........................................ ...... ..... 10
Moisture Removal .................... ........................... ................... 10
Effect of Light .......... ................................... .................. 14
Chemical Fungicides ............................... ....... ......... 15
Protection of Fabrics from Microbial Action-......................... 17
Requirements for Rot-Proofing of Cellulose Fabrics Ex-
posed to Outdoor Conditions.................................. 19
Requirements for Mildew-Proofing of Fabrics for Indoor
and Personal Use......................................... 20
General Methods for Applying Fungicides to Fabrics...... 20
Water Repellents ........... .......... .......... 21
Some Useful Textile Fungicides, Their Properties and
Methods of Application............................................. 22a
Removal of Mildew Stains from Fabrics................................. 22
Peroxide Bleach ................ ......... ..................-- -- . 24
Permanganate Bleach ........................................ .............. 24
How to Prevent Mildew on Paint............................................ 24
Preservation of Leather from Mold Attack~.......................... 27
W ood Preservation ..................................................... 30
Creosote .................................. ..... ............................... 31
Zinc Chloride ............................................ 32
Copper Naphthenate ........................................... ....... 33
Stain Control .................................................................... 85
M ildew on Books .......................................................................... 5
Mold Control in Bakeries......................................... .......-.. 87
Appendix ..... ................... .... ............................................... 40
References ...... ..................................... ..... ........ 49
In areas where warm temperatures and high relative humid-
ities exist, the damage to materials and equipment from mold
and mildew becomes quite an important economic factor. Dur-
ing the summer months, conditions in most parts of Florida
are favorable to mold growth with consequent possible economic
loss to its citizens.
During the war because of the large scale military operations
in tropical climates, the Armed Forces spent considerable time
and sums of money in investigating methods to minimize
damage from this sort to all types of military.equipment. For
security reasons, much of this material was kept confidential
and not opened to the benefit of the public as a whole. With
the cessation of hostilities, a large portion of this information
has been declassified but is scattered over many different
agencies and in many different places. This bulletin is an at-
tempt to correlate the available information and compile it into
readily usable form.
The more promising mold and mildew-proofing agents were
tested under Florida conditions for verification of their utility
for civilian usage. The results of these tests are published
herein with recommendations for protection of various materials
from damage. It is pointed out that some of the more efficient
mildew-proofing agents are highly poisonous and that a com-
promise must be reached between the degree of mold prevention
by certain chemicals and the safety of the users.
It is hoped that the reader will find the information helpful
and as new and improved methods become available, more in-
formation will be published.
JOSEPH WEIL, Director
WHAT IS MOLD
Mold is recognized a. the spotty or hairy growth occurring
on objects that are exposed to warmth and dampness. It is
sometimes called mildew, rot, or decay dc -nding upon the kind
of damage that is done. Mildew is noted as an aerial growth
and results in surface spotting, while rot and decay molds grow-
ing below the surface may be less visible but often bring about
complete deterioration. Molds are simple plants belonging to
that group of the plant kingdom known as fungi. Other familiar
fungi, quite different in appearance are mushrooms, toadstools
Although fungi are classified as plants they are like animals
in many respects. They have no roots, stems, or leaves, they
contain no chlorophyll, and they cannot synthesize their own
foods from carbon dioxide, water, sunlight, and minerals as
green plants do. Like animals they breath oxygen and give
off carbon dioxide. Fzr foods they utilize organic materials like
carbohydrates, proteins and fats. It is this ability to attack
organic matter that makes fungi both a friend and an enemy
While this bulletin treat- molds as enemies and discusses
methods of eliminating them, one should remember that life on
Fig. 1.-Penicillium notatutm, the penicillin-producing mold, showing
mycelium and spore-bearing hyphae. (Courtesy Chicago National History
The Nature of Molds
earth would not be possible without them. They are one of na-
tures' scavengers, decomposing dead plant and animal matter
and converting it to the simple materials that are needed to
maintain the life cycle in nature. Molds also bring us life-saving
penicillin (Fig. 1), as well as many valuable chemicals of com-
Fungi are very abundant in nature. A hundred thousand dif-
ferent species have been classified and many times that number
remain uncatalogued as yet. Mold particles are found in the
dust in the air, and a handful of soil may contain millions of
Looking at a growth of mildew one sees a network of threads
resembling cotton, which are topped with a mass of color,
usually black, green or yellow. If brushed off, the colored ma-
terial will be observed to be a powdery dust. Under the micro-
scope this dust would be seen as a mass of individual particles,
which are known as spores. These spores, which are so small
that they cannot be seen with the unaided eye and so light that
they float on air currents, are the seeds of the parent plant.
They are capable of remaining dormant for many years under
the most unfavorable environmental conditions and germinating
when conditions are suitable for growth.
In the first stage of germination the spore swells and puts
out one or more tubes known as germ-tubes. (See Fig 2.) The
germ tube elongates and becomes highly branched forming a
network of filaments. The name given to the individual fila-
ment is hypha while the network of filaments is called mycelium.
The mycelium may grow below the surface of the medium as
well as on the surface and extend into the air, as is seen on
moldy bread. Further along in the d-velopment of the fungus
the aerial hyphae become specialized for spore production, putting
forth the commonly recognized spore heads. In color the mycelia
are generally white while the spores may be any number of
colors, depending upon the species. The spores which are easily
scattered, propagate the species by repeating the described
It seems hardly necessary to discuss the damage that molds
do; that is all too familiar. If the damage could be assessed
in monetary values, the nation would probably be paying an
amount of more than a billion dollars every year. A major
part of this loss is in food crops that are constantly plagued
by mold diseases, but a considerable portion occurs in non-
agricultural products as well. (This bulletin will not discuss
fungus control as related to agriculture or medicine. They are
specialized subjects in themselves.)
The destruction wrought by fungus, however, cannot always
be valued in dollars and cents alone. For example, take the role
played by fungus during the war. In the hot, humid Pacific
Islands fungus diseases were unusually prevalent, producing
serious consequences with the fighting forces. These were the
parasitic fungi that attack living tissue, an example being our
fellow-traveller, the common athlete's foot fungus. But the
saprophytic fungi that attack dead matter did their share of
sabotage in the war. Combat groups taking island outposts
suddenly discovered their radio equipment would not function
because mold had grown on vital insulation so that it no longer
insulated. Photographers found their camera lenses etched and
film negatives spotted. Tents and tarpaulins rotted, ropes snap-
Fig. 2.-Stages in the development of mold. (1) Spore germinates and
sends out germ tubes, (2) Germ tubes grow and branch out, (3) Exten-
sively branched hyphae are known collectively as mycelium, (4-6) Spore-
bearing hyphae are developed. From left to right, spore heads of genera,
Aspergillus, Penicillium, and Rhizopus. (Courtesy E. I. Dupont de Nemours
Conditions for Mold Growth
ped, signs became unreadable, wood crumbled and shoes grew
beards. In all these cases -molds had been responsible.
While the severity of mold damage is not quite as extreme
in Florida as in more tropical climates the problem is much the
same. Expensive awnings rot and tear, beach chairs give way,
bread becomes moldy, books, walls and clothing show mildew
stains. Closets have musty odors which sometimes send one
into fits of sneezing because of sensitivity to the tiny mold spores
in the air.
Conditions for Mold Growth
Mold problems are at their worst during the summer months
in the period of the regular, heavy rains. Molds will grow over
a wide range of temperatures; some have been shown to grow
in cold storage rooms at temperatures below freezing, others
will withstand temperatures approaching that of boiling water.
But the optimum temperatures for most molds are between
800 and 900 Fahrenheit, which is a typical temperature range
for Florida summers.
Even more essential than favorable temperature conditions
for mold growth is adequate moisture. No matter how favor-
able all other conditions, unless there is some dampness mold
growth will not take place. During the war it was reported
that tents used in the Sahara Desert had shown evidence of
mildew. Further investigation revealed that while the air was
very dry, the cold temperatures at night caused sufficient mois-
ture to be condensed onto the cloth to support mold growth.
When the air contains adequate moisture mold spores will
germinate even though the material may be relatively dry. It
has been shown (1)* that the minimum relative humidity sup-
porting growth varies from 75 to 95 per cent relative humidity
species of molds.
While all molds require organic matter for food they differ
considerably in the types of organic matter they are able to
utilize. Some types can decompose cellulose and are responsible
for the rotting of tents and ropes. Among these are representa-
tives of the genera Chaetomium, Fusarium, and Stachybotrys.
Others are unable to attack cotton and wool fibres but utUize the
oils, starches, and simple organic compounds that exist oiSmany
cellulose and protein materials. The non-rotting, surface mold
Italic figures in parentheses denote references listed at the end.
How Mold Growth May Be Controlled
growth is generally referred to as "mildew" and is commonly
produced by members of the genera Penicillium, Aspergllus,
The quantity of food material req, 'ed for mold growth is
remarkably small. Mildew will appear on surfaces that seem
to be perfectly clean; handprints outlined with mildew will
appear on clean clothes that have been handled while being put
away. Molds require oxygen in their metabolism but are able
to start growing with very little. They obtain enough oxygen
to grow in water solutions and in paint films, although they
grow more readily when reaching the surface.
Regarding the reaction of molds to acids and alkalies, they
prefer a medium which is slightly acid or neutral but are able
to withstand wide latitudes of acidity and alkalinity.
METHODS OF MOLD CONTROL
Removal of Oxygen
Many weapons in combatting molds are merely the denial
of the conditions necessary for mold growth. For example,
molds require oxygen in their respiration. Certain foodstuffs
are preserved by vacuum packing; that is, removing the air
from the container. If any mold growth had already begun
it could not continue long before all traces of oxygen would have
been removed and mold growth thereby terminated. During
the war another technique was used quite extensively to remove
oxygen. In shipping many types of perishables, the air was
removed by displacing it with inert gases such as nitrogen and
carbon dioxide, and the container was then sealed to prevent
entry of oxygen.
Removal of Nutrients: Cleanliness
The removal of food for mold metabolism is one method of
controlling mold growth. It is well known that freshly cleaned
clothing is less likely to become spotted with mildew than cloth-
ing which is soiled and stained with grease. As previously
mentioned, the quantity of food required by molds is very small.
The perspiration from one's hands, or the quantity of soap left
after rinsing, or the dust particles deposited from the air can
supply sufficient nutrient to permit unsightly mildew to appear
when other conditions for mold growth are favorable. There-
for,. cleanliness alone cannot be depended upon to completely
check mold growth.
Temperature and Moisture Control
Temperature control is an aid in combatting mold. High
temperatures are useful in pasteurization and sterilization pro-
cesses, while low temperatures permit cold storage. Sterilization
provides for the destruction of all micro-organisms and requires
a higher temperature than pasteurization which only reduces
the number of organisms. The mold mycelia are easily killed
by heat while the spores are more resistant to destruction.
Moisture accelerates killing at high and low temperatures. Hot
water or steam is more effective than dry heat at the same tem-
perature. In a like manner the spores of many species of molds
are destroyed by freezing in the presence of water but when
dry can be cooled in liquid air without harm. Cold is not as
destructive as heat, for while heat may kill, cold merely inhibits
the life processes and growth occurs again when a favorable
temperature is reached. A temperature of 320F. (freezing)
will prevent growth and germination of the spores of all but
a few molds. Boiling water will kill all vegetative mold and
practically all spores, depending upon the time they are exposed
to this temperature.
A practical method of restricting the proliferation of mold
is the regulation of available water. Mold grows well on a
dilute sugar or salt solution providing all other growth require-
ments are satisfied. However, by increasing either the amount
of sugar or of salt in the solution, a concentration will be
reached where mold will fail to grow. This is due to the fact
that the mold cannot obtain sufficient water to permit it to utilize
the nutrients present. The same quantity of water is present
as before but the sugar or salt compete for it and prevent it
from becoming available to the mold. Salting and sugaring
are time-honored methods for the preservation of foodstuffs.
On dry materials a regulation of the moisture in the atmos-
phere will produce the desired results. When the air has rela-
tive humidity of 95 per cent, that is when the air contains 95
per cent of all the water (in the form of vapor) it can hold at
its temperature, molds readily obtain sufficient water from the
air. At 70 percent relative humidity, or below, molds cannot
obtain the required amount of moisture and growth is termi-
Such a condition may be brought about in either of two ways.
The first involves increasing the water-holding capacity of the
RemovL. ,.f Water to Prevent Mold Growth
air; the second, removing wat-c from the air. The amount of
water that air can hold depends upon its temperature. As the
temperature increases the water-hu :ing capacity increases. For
example, the weight of water, in gra-- iner pound of dry air,
that air can hold at 400F. is 36, at 800F. is 155, and at 1200F.
is 569. Therefore it can be seen that a small increase in tem-
perature can markedly increase the air's capacity for water. If
the water-holding capacity is increased but the amount of water
remains the same, the relative humidity will be lowered. This
principle is illustrated in the home when the furnace is started
during rainy weather to get rid of dampness. Keeping an elec-
tric light burning in a closed closet is a procedure which has
often been used to retard mildew growth.
Materials which remove moisture from the air are known
as dessicants. Two dessicants of industrial importance are cal-
cium chloride and silica gel. They are both used as small granules,
white in color, and are non-poisonous chemicals. Calcium
chloride takes up twice its weight of water and becomes a thick
solution while silica gel takes up only one-half its weight of
water but retains its dry form. Calcium chloride is less ex-
pensive than silica gel but the latter may be used over and over
if it is regenerated. Regeneration is accomplished by heating
the silica gel in a dry oven for several hours at 3000F. to 3500F.
The dessicants are used to keep storage rooms, closets and
cabinets below the safety line of 70 per cent relative humidity.
A simple device (see Fig. 3) for keeping closets in the home
dry consists of a quart-sized waxed cardboard container, a tubu-
lar section of a pint-sized container, a perforated cardboard
disc or a round piece of stiff screening, and a pound of calcium
chloride. The calcium chloride can be bought in economical
bulk form or bricketted into cylindrical shapes as shown in the
photograph. The dessicant material should always be kept in
an air-tight container until ready for use. To use the calcium
chloride dessicant, the section of the pint-sized container is
placed inside the quart container, the perforated disc is placed
flat on top of the section and the calcium chloride is put on top
of the disc. The quart container is not covered when in use. The
unit is placed on the floor or the shelf of the closet, but prefer-
ably on the shelf since moist air is lighter than dry air and rises.
As the moist air is dried it becomes heavier and circulates to-
wara the bottom of the closet. The moist air then rises and is
subsequently dried. When the calcium chloride absorbs moisture
Dessicants for Dehumidifying Air
it goes into solution. The solution drops through the holes in
the perforated disc or wire screening into the bottom of the
container leaving the solid calcium chloride above to take up
more moisture. After all the solid calcium chloride has dis-
appeared, which may take from two weeks to two months de-
pending on the humidity, the liquid can be poured down the
drain and a charge of solid calcium chloride replaced. The liquid
should not be permitted to come in contact with clothes as it
can deteriorate the fibers. If it should accidently splash onto
clothing, it should be immediately washed out with water. More
permanent dehumidifying units employ glass or metal in place
of the cardboard container.
Because it remains a dry-feeling, non-corrosive solid silica
gel granules may be scattered into clothing and other articles
Fig. 3.-Simple container for calcium chloride dessicant. Parts are
waxed container, section of smaller-sized container, perforated cardboard
disc, calcium chloride cartridge, and container cover. When in use the
cover is removed and the parts are placed into the container as shown in
Silica Gel as a Dehumidifying Agent
that are to be stored in closed "hests or trunks. It may be used
in closets (Fig. 4) like calcium chloride but approximately four
times as much is required. However, it can be placed in an
open pan in the closet and then be regenerated in an oven when
saturated with moisture. To determine when it is saturated,
.___ .I. 1
Light Rays to Control Mold Growth
a few granules of "tell tale" silica gel may be thrown in with
the ordinary product. Tell-tale silica gel is the ordinary product
treated with cobalt chloride so that it is blue when fresh and
pink when saturated with moisture. No matter which dessicant
is used it is important that the closet or cabinet be as air-tight
as possible and be kept shut when not in use, otherwise the
dessicant will be unnecessarily wasted.
More complicated industrial-type dehumidifiers for use in
ware houses and storage rooms are available. They provide for
air circulation, continuous dehumidfying, and automatic re-
geration of the silica gel or other dessicant.
Effect of Light
Since molds contain no chlorophyll and do not synthesize
their carbohydrate foods as green plants do, they can get along
perfectly well in absolute darkness. As a matter of fact, it has
long been known that sunlight has a definite retarding effect
on microbe proliferation. More recent investigation has shown
that not all light rays in sunlight are equally toxic to micro-
organisms, and that the ultraviolet rays are more toxic than
the visible and infra-red rays. A potent weapon in the form
of lamps that generate strong ultraviolet radiations has been
produced for combatting molds, bacteria and other micro-
organisms (Fig. 5). Until a few years ago, ultraviolet lamps
that generated highly germicidal rays were very expensive to
Fig. 5.-Germicidal ultraviolet lamps sterilize air and help to prevent
mold contamination in bakeries and food plants. (Courtesy Westinghouse
install and costly to operate, thereby restricting their use. New
research developments have led to a lamp which is inexpensive
to install and operate and is an extremely potent germ killer.
It has been put to many uses already and its applications are
rapidly increasing. The germicidal lamps are used in hospitals
to purify the germ-laden air, in schoolrooms and in factories
to reduce air borne diseases. In meat storage rooms properly-
installed lamps not only cut down contamination from the air but
also reduce growth on the meat surface to an extent equivalent
to a ten degree lowering of the temperature below the 40-45
degree range. The ability to keep the meat at a higher tempera-
ture and humidity, without spoiling permits better curing and
less spoilage trim. In bakeries, in dough proofing rooms, and
in the slicing and wrapping operation, the ultraviolet lamps
are an aid in combatting mold contamination.
The following facts should be considered regarding the use
of the germicidal lamps. Ultraviolet light is lethal to the micro-
organisms it strikes, providing sufficient exposure is permitted.
However, it does not inetrate and therefore, will not kill
microbes beneath the surface. For example, the surface of
cheese may be sterilized by passing it under an ultraviolet lamp,
however, any contamination inside the cheese will be unaffected.
It should be pointed out that molds. are much more difficult to
destroy by irradiation with ultraviolet light than bacteria. The
mold spores are resistailt to ultraviolet rays; it takes 45 tmnes
as much radiation to kill mold spores as it does to kill bacteria.
Therefore. where molds are the principal contaminants, suf-
ficient time should be permitted for killing the spores. Since
the ultraviolet rays are harmful to the eyes and excessive ex-
posure to the skin will produce "sunburning", care should be
taken in making proper installations of the lamps, in utilizing
sunglasses and taking other protective measures where needed.
A fungicide is a material which is capable of killing fungi.
Some materials do not kill fungi but merely prevent their pro-
liferation. Such materials are called fungistats or mold in-
hibitors. For this discussion, however, the term fungicide will
be used inclusively in referring to all the chemical tools for
fighting mold, mildew, rot, and decay.
These fungicidal chemicals act as poisons to molds. Some
of the chemicals exert their toxicity by combining with and
precipitating the protoplasm of the fungus; others act by inter-
How Chemicals Prevent Mold Damage
fering with the enzyme systems that provide for cell respiration;
still others remove vital elements that the fungus requires for
metabolism. Since mold species differ in their metabolism, they
differ also in their reaction to fungicides. Copper salts for
example are extremely toxic to many of the cellulose-decompos-
ing fungi, suppressing growth at 0.001 percent of copper sulfate,
Fig. 6.-For best results outdoor fabrics must be able to withstand
deterioration resulting from rain, sun, and rot. These exposure tests are
set up to determine the most satisfactory treatments for fabrics used in
Protection of Fabrics
while some of the surface-growing molds (mildews) require
1 to 2 percent of copper sulfate before growth is inhibited. It
is seen, therefore, that in general, copper salts are well suited
for rot protection of cellulose but are not to be recommended
for preventing the growth of the surface molds. Salts of mer-
cury on the other hand are extremely toxic to molds when applied
to surfaces; however, they are ineffective on materials coming
in intimate contact with the soil.
The particular use of the fungicide as well as the specific
types of fungi it combats are important. For tents, awnings
and textile bags (Fig. 6) the fungicide must be very resistant
to leaching and sunlight, should be non-volatile, and preferably
colorless. For articles of personal use, the fungicide used must
be odorless and not a skin irritant. F.r foodstuffs the toxicity
is the most important factor. The fungicides used to prevent
mold from growing on bread must have different characteristics
from those used to prevent mold from growing on paint.
Fungicides are found in different chemical groups. There
are salts of the heavy metals such as silver, mercury, cadmium,
copper, lead, and zinc. The compounds of sulfur form another
group that have had widespread use in agriculture and in medi-
cine. Phenol, the first antiseptic to be used ip surgery, is the
parent of a series of compounds including the cresols and chlori-
nated phenols which have decided fungicidal properties. Many
of the fungicides now in use contain a combination of the fungi-
cidal groups, thus having greater effectiveness on more types
PROTECTION OF FABRICS FROM MICROBIAL ACTION
Different textile materials are affected in different ways by
microbial invaders. Synthetic fibers like nylon, saran, and
acetate rayons do not support mold growth and are very im-
pervious to the molds' digestive enzymes. This does not mean
that fabrics or ropes made from these plastic fibers will not be
prey to the unsightly surface-growing molds. The plastic fibers
do not inhibit molds; therefore, if the fabrics become soiled with
materials that are nutrients for fungi, the mildew will appear.
Silk is a natural protein fiber which, like the synthetics, is
highly resistant to deterioration by fungi. In making para-
chutes during World War II advantage was taken of this prop-
erty of silk. It was recommended that linen reinforcements
Protection of Fabrics
of parachutes be replaced by silk tape. Silk canopies used on
man-dropping parachutes required no mildew-proofing treat-
Wool is also a natural protein fiber that is resistant to de-
composition by molds. If woolen fabric is permitted to remain
wet or damp for long periods of time, however, bacterial de-
terioration will occur which in sufficient time will rot the fabric.
When clothing and other fabrics made of wool become soiled
with grease, dirt, or perspiration, the fabric becomes susceptible
to the surface-growing molds. While these molds will not de-
teriorate the fibers, they detract from the appearance of the
garment or fabric. In addition, the mold may exude materials
which react with the fabric dyes, discoloring or bleaching the
fabric in spots and thus making it unusable.
Cotton is by far the most abundantly used textile material.
It is composed almost entirely of cellulose, a carbohydrate ma-
terial made up of chains of dextrose sugar molecules. While
all humans and some fungi lack the enzymatic keys which
release the sugar held in the cellulose molecule, other types
of fungi are capable of devouring this sugar with great
ease. These cellulose-decomposing fungi are very abundant in
Fig. 7.-How soil microbes rot fabric. Cotton duck strips (left to
right) show how strip looked originally and how they deteriorated after
being buried in soil for 2, 5, 7, 9, 12, and 14 days, respectively. (Courtesy
of U. S. Bureau of Human Nutrition and Home Economics.)
Rot-Proofing Cellulose Fabrics
the soil (see Fig. 7) and their spores are present with the dust
in the air. Coming in contact with cellulose they envelop it
with their hyphae and digest it by means of the enzyme cellu-
lose. The fiber is first tendered or weakened and eventually
rotted through. Sometimes surface-growing molds may start
acting on the waxy exterior of the cotton fibers. When they
have removed the waxy exterior, the fibers are easily wetted
and the cellulose-rotting fungi begin their work. In addition
to the action of the fungi, the destructive action of the sun's
ultraviolet rays, and the alternate contraction and expansion
of the fabric as it gets wet and dries tend to cause the threads
to weaken and pull apart.
Requirements for Rot-Proofing of Cellulose
Fabrics Exposed to' Outdoor Conditions
Under this category would come awnings, beach chairs,
canopies, beach umbrellas, tents, tarpaulins, ropes, nets, filter
1 2 2 '4
Fig. 8.-Rope samples after having been immersed in sea water for 6
month: (1) Untreated; (2) 6 percent pine tar; (3) 4 percent waterproof-
ing oil containing lead soap; (4) 4 percent waterproofiing oil, containing
lead soap, plus copper naphthenate (1.5.percent copper); (5) 6 percent
pine tar and copper naphthenate (1.5 percent copper); (6) copper naphthe-
nate (1.5 percent copper). (Courtesy National Research Laboratories,
Requirements of Preservatives
cloths, sails and fabrics used for many agricultural and indus-
trial purposes. It is obvious that many of the methods of mold
control already discussed such as humidity control, temperature
adjustment, removal of oxygen, etc., would not be practical for
the protection of fabrics that must perform outdoor service.
To prevent deterioration one must use a material which does
not rot (these are relatively expensive) or use cotton treated
with a preservative. Jute, hemp, and sisal fibers used in' making
ropes (Fig. 8) are cellulosic in nature and require preservation.
The requirements of such a preservative are very rigid. (1) It
must be easy to apply and difficult to remove. (2) It should
not be removed by water and should not be affected by sunlight
and weathering. (3) It should be safe to handle and preferably
be non-toxic to humans and animals. (4) It should preferably
be colorless, odorless, inexpensive, etc. (5) It should not weaken
the fibers by chemical action on weathering, and (6) It should
be effective when in contact with the soil.
While no fungicide has yet been developed that meets all the
many requirements, there are a number which have given satis-
factory service under severe tropical conditions during the
war (3). Some fungicides developed during the war and tested
under tropical conditions in the Panama Canal Zone (4) will
be discussed and methods of their application to fabrics will be
Requirements for Mildew-Proofing of Fabrics
for Indoor and Personal Use
Many of the fungicides used for outdoor service have decided
odors and colors and would not be suitable for use on clothing
or draperies in the living room. The requirements here place
emphasis on a fungicide that is colorless and odorless and that
does not change the appearance or the feel of the fabric. The
preservative should be non-toxic, non-irritating to the'skin, and
preferably resistant to removal by laundering and dry cleaning.
No one fungicide has yet been produced that will meet these
rigid requirements although a few are satisfactory in some
General Methods for Applying Fungicides to Fabrics
The simplest method for treating fabrics is to dip them into
a solution of the fungicide dissolved in a volatile solvent. This
is known as the single bath treatment. The two bath treatment
necessitates dipping the fabric first in one solution and then
Methods of Application of Fugicides
into another solution. The aqueous dispersion method is a single
bath treatment in which the chemical preservative is suspended
in fine particles but not dissolved in the solvent. The latter
method is not preferred, but is sometimes used with a fungicide
that is not soluble in common cheap solvents.
After the fabric is dipped or run through the chemical solu-
tions the excess liquid is squeezed out by means of a clothes
wringer, mangle, or padder. The rolls of the squeezers are
adjusted to permit the desired amount of liquid to remain. In
most cases using cotton fabrics the fabric is permitted to retain
a weight solution equivalent to 50 percent of the weight of fabric
treated. This is referred to as 50 percent pickup. Assuming
a 50 percent pickup, one gallon of fungicidal solution will treat
roughly 80 yards of an 8 ounce duck cloth. When using the two
bath treatment, it is only necessary to pass the fabric through
the rolls after the first bath. The fabric is put directly into the
second bath without drying.
For treating ropes and nets, it is necessary to permit them
to soak in the treating bath until the solution has penetrated
to the center of the rope. This may take from a few minutes
to many hours depending upon the solvent used and the tight-
ness and diameter of the rope.
Dipping the fabric into the treating solutions is the preferred
method wherever possible since all the fibers are then evenly
wetted. However, should the bath method be inconvenient in
certain cases, the solution can be applied by brushing, spong-
ing, or spraying the fabric. If these methods are used consider-
able care should be taken to see that no parts of the fabric re-
main untreated and that the solution has been applied uniformly.
It should be stated here that many fabric preservative treat-
ments are more effective when a waer-repellent agent is also
applied. Water repellents are applied by incorporating them in
the baths or by a separate process following mildew-proofing.
The solvents used in treating ropes may remove water-proofing
waxes and lubricating oils from the rope which may have to be
re-waxed or re-oiled if that is desired. Likewise the presence
of waxes and greases on the fibers may slow up the penetration
by the solvent. Some chemical treatments are water-resistant
and do not require additional water-repellency. Others are not
compatible with water-repellent chemicals. Common water re-
Removal of Miklew Stains
pellents are wax-aluminum acetate emulsion, metal soaps such
as lead stearate, and organic compounds of the "Zelan" type.
Waxes, resins, and rubber are used to water-proof fabrics. The
subject of water-repellency is complex and will not be considered
A Table of Some Useful Textile Fungicides
The table that is inserted lists some useful textile fungicides
giving their properties and methods of application to fabrics.
The appearance of fabric strips treated with these fungicides
following one year's outdoor exposure is shown in Fig. 9.
Removal of Mildew Stains from Fabrics
Mildew stains are sometimes very difficult or impossible to
remove without altering the fabric. It is therefore stressed
that the proper precautions, already described, to prevent mil-
dew growth be taken rather than attempting to remove it once
it has appeared.
As stated before, fungi may damage fabrics in a number
of ways: (1) by weakening the fiber; (2) by causing spotting
or discoloration due to the mold itself; (3) by causing spotting
resulting from chemical reaction between the mold metabolic
products and the dye in the fabric; (4) by preventing the fabric
from taking the fabric dye evenly at the mill.
There is little that can be done if the fungus has weakened
the fibers or if it has produced uneven dying of the fabric. The
staining produced by the fungus itself or by the metabolic
products of fungus growth may sometimes be removed. Dry
cleaning or laundering may remove the spots. If not, special
spotting treatment may be tried.
For home treatment the stained part should be rubbed with
a paste made of a neutral soap and water, then rinsed and al-
lowed to dry. Then try a dry-cleaning solvent. If the stain
has not been removed, lemon juice or vinegar may be applied
and the fabric dried outdoors in strong sunlight. This will tend
to bleach the stain color. Stronger bleaches may be used if the
fabric is not dyed. Household bleaches containing sodium hypo-
chlorite should be thoroughly rinsed after treatment as this
chemical will deteriorate the fibers if allowed to remain in the
cloth. Two other bleaches for stubborn stains are as follows:
SOME USEFUL TEXTILE FUNGICIDES, THEIR PROPERTIES AND METHODS OF APPLICATION
lenpte rRr Nets
Effective in low concentrations.
Resistant to rain and sunlight.
Almost odorless. Low in toxicity.
Widely used by armed services.
Inexpensive. Effective. Safe.
Can be applied with single bath
solution of cheap organic sol-
vents. Is water repelling.
See illustration on pg. 19 and
Same advantages as copper
naphthanate but in addition it
It has no odor (once the am-
monia has evaporated). Does
not stiffen the fabric. May be
applied from a water solution
in a single bath.
Outdoors Colorless. Slight antiseptic-like
Indoors odor. Low in toxicity. Effec-
Outdoors Colorless, odorless, water repel-
lent highly fungicidal. Not
leached by rain or deteriorated
Practically no odor
non-irritating to the
Has a yellow-green color. Should
have water-repellent treatment
when used in contact with solL
Strong greenish-blue color. Odor
resembling petroleum. Large
amount retired for protection.
Only about half as potent a fungi-
cidal agent as copper napthe-
nate. Since twice as much is
needed for protection equivalent
to copper naphthenate, the stiff-
ness resulting is much greater.
Blue-green color. Not very ef-
fective against surface-growing
molds, reached by severe
Not as effective as many of Lhe
copper compounds when in con-
tact with the soil. Should be
used with a water repellent for
Since it contains mercury, this
compound is highly poisonous if
taken internally, although it is
much less poisonous than many
mercury compounds in indus-
trial use.**** It is not effec-
tive on fabrics coming in con-
tact with the soil. Relatively
Removed by laundering and dry
cleaning. Is not satisfactory
for severe outdoor exposure(l1).
1.5 (0.3 copper)
(Approx. 3% solution of 8-quinolnol acetate.) To 4 oz.***
of 8-quinolinol add 8 oz. (7.3 fl. oi.) of glacial acetic acid.
Heat to 185*F. until dissolved. (Danger: Hot glacial
acetic acid and its fumes are very dangerous. It is also
inflammable. If the acid gets on skin or clothes, wash
quickly with a saturated solution of baking soda in water
or soap and water.) Dilute to I gal. with water and 1 tea-
spoonful of "Santomerse S" or kny satisfactory wetting
(Approx. 2% solution
of cupric acetate.) Dis-
solve 3 oz. of enpric
acetate in 1 gal. of
5 (0.4 copper) (Approx. 10% solution of copper: naphthenate.) Employ- None
ing a copper naphthenate paste containing 8% copper,
dissolve 13.5 oz. in 1 gal. of solvent. The solvent may be
either petroleum naphtha, mineral spirits, or kerosene.
10 (0.8 zinc)
45 (1.5 copper)
1.0 (0.4 mercury)
(Approx. 23% solution for ropes larger in diameter than
%". Approx. 11.5% for ropes smaller than %".) For
the 23% solution dissolve 37 oz. of copper napthenate paste
(8% copper) in 1 gal. of petroleum solvent. For the
smaller ropes dissolve 18.5 oz. of paste in 1 gal. of solvent.
(Approx. 20% solution of zinc naphLheznaue.) SO oz. of a
zinc naphthenate paste containing 8' zinc are dissolved
in 1 gal. of a petroleum solvent such as naphtha, kero-
sene, or mineral spirits.
(Approx. 9% copper ammonium, fluoride.) Copper am-
monmum fluoride may be obtained as a powder containing
20% copper or as a sludge containing 10% copper (8).
Mix 2.5 lb. of the 10% solution with 5.5 lbs. (6.3 pts.) of
water, or 8 parts of the 20% powder with 17 parts by
weight of water. Add 1 oz. of Aerosol O.T. (10%) (9) or
other suitable wetting agent.
(Approx. 2% alkaline solution of dihydroxy-dichloro-
diphenylmethane.) Add 2.5 oz. of the fungicide and 0.5
oz. ofcaustic soda flakes to 1 lb. (pt) of water and stir
until dissolved. Then dilute to 1 gal. with water.
(Approx. 2% solution of pyridyh ercuric stearate.) Add
2 oz. of the compound to 1 gal. of turpentine. Be careful
not to get any of this solution on the skin. Keep away
(Approx. 0.5% solution of saliclanilide.) Dissolve 0.5
oz. of salicylanillide in 1 gal. of isopropyl alcohol (rub-
(Approx. 5% solution
of acetic acid). Add 6.5
os. (.9 f. oz.) of gla-
cial acetic acid to 1 gl.
For single bath aqueous dispersion
method of application see reference
Method of Application
Using a wringer or mangle, adjust
.he rolls to give 50r/ pickup (see
Igr. 21) and pass the fabric through
the first bath at 185'F. Without
drying, pass the fabric through the
second bath at room temperature.
Wash the fabric with water and dry.
The fabric is dipped into the solution
and squeezed through the rolls ad-
justed for 50% pickup.
The rope or netting should be dipped
into the bath and permitted to soak
until the liquid has penetrated the
rope. Since smaller ropes pick up
much more solution, the concentration
of copper napthenate in the bath is
cut in half.
Same as for copper naphthenate. Zinc naphthenate is useful in treat
ing awning since it does not change
their color. It is claimed that til
treatment has a tendency to revive
the color of faded awnings.
The fabric may be dipped and squeezed Similar treatments utilize copper am-
or the solution applied with a brush monium hydroxide. (See Appendix.)
to obtain 50% pickup. The solution
has a strong ammonia odor. The
ammonia is removed by air drying
or by drying with heat.
The fabric is treated with the first so- Consult reference (10) for one batil
lution then squeezed, permitting 50%
pickup. It is then passed through the
second bath, washed with water, and
dried. A water repellent may then
Permit 50% pickup of the solution.
Then allow to dry in air.
Dipping the fabric in this solution is
the best way to get complete coverage.
However, the solution may be sponged
or sprayed onto clothing, blankets,
curtains. etc.. if it is more convenient.
method of application.
In low concentrations, this compound;
is not a strong skin irritant (11).
Some persons are extremely sensitive
to mercury and show skin reation
when contacting even minute qua
titles of mercury compounds.
should avoid this and other mercury
This product was developed in Eng-
land in 1928 (18) and has given yeas
of satisfactory service as a preserva-
tive for cotton and woolen goods in
storage and in shimnent.
Bome of the trade nam for proprietary products employing these chemicals are given in the Appendix.
'* s percent i based upon the weihtt of th fhbrl&.
** Avo po (wetiht' ouaam an uml thnmroaout thi bulletin except where otherwise speciied.
* If l mseeey pr bo are aldemtaUL take intenally take white of as or milk and call a physeian immedistelb.
The petroleum solvents are inflami
mable and should be kept away from
flames. For other formulations using
copper naphthenate see reference (#f.
Pine tar, waxes, wtter-prooflng oils
and soaps may also be applied to the
rope to give weighing and non-slip
characteristics. These products are
dissolved in the solvent along with fbe
copper naphthenate of desired.
- I I .. _.
I - - I
Fig. 9.-Cotton duck strips exposed to outdoor weathering
for one year. Refer to inserted table.
117 No treatment
106 1% Copper 8-quinolinolate
113 1% Copper Naphthenate
2 1' Copper Ammonium Fluoride
119 No treatment
94 1% PyridyLmercuric Stearate
67* 1% Dhydrox-Dichloro Diphenylmethane
71* 1% Maltylanlde
* Also had water repellt treatment
Note: Blak color at ede of strive is dirt not mold.
Mildew on Paint
1. Peroxide Bleach (14)
To four fluid ounces of water add one fluid ounce of com-
mercial (3 percent) hydrogen peroxide solution and one tea-
sponfthfuo household ammonia water. Moisten the spots fre-
quently with this solution and rinse in water.
2. Permanganate Bleach (15)
Dissolve one ounce of potassium permanganate in a gallon
of water. Immerse the fabric for 15 minutes. The fabric will
be brown when removed. Then immerse into a solution made
up of 3 ounces of sodium bisulfite dissolved in a gallon of water,
and rinse with water. The second bath will remove the brown
color. The process may be repeated if necessary.
If the fabrics to be spotted are colored, any treatment should
first be tested on an inside seam or other inconspicuous place
to make sure that the treatment itself does not affect the color
of the fabric.
HOW TO PREVENT MILDEW ON PAINT
The regular rainfall, high humidity, and high temperatures
that occur in Florida during the long summer season make
paints and protective coatings highly vulnerable to attack by
mold fungi (Fig. 10). Outdoor paints that are mildewed appear
to be spotted with dirt. It is sometimes necessary to use a
microscope to determine whether a painted surface is mildewed
or merely dirty. As a rule mildew spots which pepper the
Fig. 10.-Exposure tests at Gainesville to determine resistance of paint
formations to mildew. (Courtesy of Mr. R. Buckley.)
Why Paintm Mildew
surface of the paint are much more difficult to wash off than
dirt. Growth of mildew on interior surfaces is generally char-
acterized by the fuzzy, hair-like nmycelia rather than the dirt-
like specks in exterior paints. Shaded exterior surfaces which
are near trees and shrubbery, or other sources of moisture, are
likely to mildew more readily than sunny, dry southern ex-
posures. The interior paints of poorly ventilated rooms, bath-
rooms, kitchens, bakeries and food plants are subject to mildew-
Chemically, most paints are made up of a volatile solvent and
an organic resinous material which binds a colored inorganic
pigment. The pigments do not support mold growth but they
may supply inorganic chemicals which are required for growth.
The resinous vehicle itself or its impurities may support mol?
growth. For example, many oil paints employ linseed oiL This
oil can be utilized as a foodstuff by molds if the additional essen-
tial materials and proper environmental conditions are present.
The impuiities in the oil, as well as the essential elements added
in the pigment and drier, make it possible for the mold to utilize
the oil as a source of energy. It has been shown (16) that the
rate of growth of fungi on paint films is related to the amount
of the impurities in the oil.
The drying speed and water resistance of the paint film
influences its susceptibility to mildew. For this reason paint
films made from heat-bodied oils are more resistant to mildew
than films made from blown or untreated oils. The addition
of tung oil and spar varnishes to linseed oil paints make them
more impervious to water and more resistant to mold growth.
These vehicles speed the drying time and furnish a hard surface
to the film, thus decreasing the chance for the mold spores to
infect the film while it is tacky and for them to adhere to the
hard, slick surface when the film has dried.
Zinc oxide is a pigment which has the property of effecting
hard drying of the film and is extensively used in mildew-re-
sistant finishes. In addition to its effect on the physical prop-
erties of the film, zinc oxide is the only commonly used pigment
which has been recommended to effectively inhibit mold pro-
liferation (16, 17, 18). Other zinc pigments such as lithopone
and zinc sulfide do not exhibit this toxic effect.
Some of the synthetic resins have been shown to be less
susceptible to mold proliferation than linseed oil. Urea-formalde-
hyde, phenol-formaldehyde, cellulose acetate, ethyl, cellulose,
Treating Pant to Prevent Mildew
polystyrene, vinylites, and chlorinated rubber do not support
mold growth. Oil-rich alkyds, melamine-formaldehyde and nitro-
cellulose are susceptible to mold growth (19, go, 21).
While some resins do not satisfy the growth requirements
for mildew organisms, they cannot be depended upon to be free
of mold where dust and dirt may collect on the painted surface.
The only way to insure against mold growth is to incorporate
a toxic material in the paint. For a number of years Dr. Henry
A. Gardner and his associates of the National Paint, Varnish and
Lacquer Association have been testing the effectiveness of a
great number of fungicides on paint films under field test condi-
tions. Their results, (22) and those of other research workers
demonstrate the outstanding effectiveness !f mercury comn
pounds as fungicides for paints. Under ordinary conditions
bichloride of mercury has been shown to give complete protection
from mildew when incorporated in paint. to the extent of 1 part
of the toxicant to 500 to 900 parts of paint The quantity of
the toxicant required will depend upon the severity of the con-
ditions that promote mold growth. Other fungicides not con-
taining mercury require 1 part or more of the toxicant to each
100 parts of paint to prevent the appearance of mildew.
Because of the poisonous properties of bichloride of mer-
cury, it has been recommended (23) to use it in the form of a
paste which the painter can readily mix into the paint. A
formula for such a paste is as follows:
Bichloride of Mercury ............ 0.3 ounces
Zinc Oxide ... .....0 ounces
Linseed oil ........-. .......... 7 ounces (7.5 ounces)
Mixing this paste into 1 gallon of paint (weighing approxi-
mately 16 pounds) will give a concentration of 1 part of bichlor-
ide of mercury to 850 parts of paint. Somewhat more paste
can be used if -the mildew conditions are very severe. Pastes
such as these are available on the market.
Bichloride of mercury can be easily mulled with a small
amount of linseed oiL One-half ounce of bichloride of mercury,
mulled in oil, added to a gallon of paint will give a concentration
of one part of toxicant to about.500 parts of paint. This con-
centration should give practical assurance of freedom from
Some other compounds of mercury have the advantages of
being much less soluble in water and much less poisonous to
humans than the bichloride. These include inorganic mer-
Preservation of Leather
curials as mercuric oxide and calomel, and organic mercury com-
pounds as phenylmercuric acetate, phenylmercuric oleate, mer-
curic naphthenate, phenylmercuric naphthenate, and pyridyl-
mercuric stearate. The last four mentioned have the further
advantage of being soluble in oil. One ounce of any of these com-
pounds to a gallon of paint should protect the paint from mold.
For indoor use in homes, factories, breweries, 'etc., where
mercury fungicides are too dangerous to use, thymol, tetrachloro-
phenol, and pentachlorophenol in the concentration of 1 percent,
or greater, may be effective.
For red, brown, or dark colored paints, Gardner recommends
5 percent or more of red cuprous oxide. For greens he found
5 percent or more of Paris green to be effective.
Before painting over a mildewed surface 4t is good practice
to scrub the surface with a strong abrasive soap. Cleaning
agents as sodium pyrophosphate or trisodium phosphate are
very good for this purpose. After scrubbing, rinse well with
clear water and allow che wall to dry thoroughly before painting.
For surfaces which are badly molded, an application of a bi-
chloride of mercury solution, one part of bichloride in 300 parts
of water, is recommended. Care should be taken not to get this
solution on the skin. Instead of the use of bichloride, the wall
may be disinfected by washing with a solution made of 2 ounces
of carbolic acid in a gallon of water, or the same concentration
of a solution of household bleach. The wall should then be
rinsed with water. When the surface has dried, the paint may
be applied without fear of mildew coming from the undersurface.
PRESERVATION OF LEATHER FROM MOLD ATTACK
Leather goods are very susceptible to attack by mildew
(Fig. 11). The leather itself is not utilized by the fungi, but
the surface of the leather may be deteriorated. Tests at the
National Bureau of Standards (14) have shown that mildew not
only stains leather but increases its stiffness, weakens the grain
surface, and causes a loss in tensile strength and decreased
stretch at the breaking point. While the leather protein is not
attacked by fungi, the oils, greases, tanning materials and soluble
constituents of the leather serve as food for molds. The de-
preciation in the leather as a result of mold growth may be
largely due to the removal of the protective oils and grease.
Vegetable tanned leather becomes moldy much more readily
Mildew-Proofing Treatments for Leather
than chrome-tanned leather. This is true because the chrome
tanning exerts some mold-inhibiting influence and because it
is more water resistant after being treated with greases and
waxes. The components of vegetable tanning do not inhibit
mold growth but on the contrary act as growth nutrients. The
fungi attacking leather are for the most part the surface-grow-
ing genera Penicillium and Aspergilus.
Leather may be mildew-proofed by spraying a fungicide so-
lution onto its surface. The leather may also be treated by
incorporating the fungicide in a grease dubbing or a wax polish
that is applied to the leather.
For mildew-proofing leather goods by the solution method, a
number of fungicides have been found to be satisfactory (25, 26)
Among these are p-nitrophenol, p-chloro-m-xylenol, p-chloro-m-
Fig. 11.-An extreme case of mildew on shoes.
Formulas for Waterproofing and Fungus Proofing Leather 29
cresol, salicylanilide, and dihydroxy-dichloro-diphenylmethane.
These compounds prevent the growth of mold on the leather when
they are used in sufficient concentration but do not affect the
leather. For adequate protection, an alcohol solution of 0.5
percent of salicylanilide, p-nitrophenol, dihydroxy-dichloro-
diphenylmethane applied to the leather should suffice. For
leather goods to be used in prolonged contact with the body,
dihydroxy-dichloro-diphenylmethane is to be preferred. The so-
lution is prepared by simply dissolving 0.5 ounce of the compound
in 1 gallon of rubbing alcohol.
A dubbing is a grease or oil which is applied to boots, shoes,
harnesses, etc., to prevent them from absorbing water. Since
the constituents of the dubbing themselves are attacked by mold,
a higher concentration of the fungicide is necessary. A regular
Army dubbing formula is as flolows:
Beef tallow ......................................... 50 percent by weight
Neatsfoot oil ............................................. 40 percent by weight
Mineral wax ................................................ 9 percent by weight
Aluminum stearate ...... ................... 1 percent by weight
A mixture of fungicides that have been recommended for
this.dubbing which was found non-irritating to the skin when
incorporated in the dubbing is given (27). The fungicides are
used in the dubbing above, replacing part of the beef tallow.
Any single fungicide may be used in a concentration of 2.4 per-
cent but a combination is preferred because three fungicides
will give better protection against a wider variety of molds than
p-Nitrophenol ....................................... 0.8 percent by weight
p-Chloro-m-Xylenol ........................... O percent by weight
Tetrachlorophenol ............................ 0.8 percent by weight
A dubbing formula developed by the National Bureau of
Standards is as follows:
Paraffin wax ....................................... 20 percent by weight
Stoddard solvent ....................................... 68 percent by weight
Cyclohexanol ................................. 10 percent by weight
Dihydroxy-dichloro-diphenylmethane .... 2 percent by weight
For treating the outer leather of dress shoes against mildew
the incorporation of dichloro-dihydroxy-diphenylmethane in the
shoe polish is simple and effective. If the polish is a solid wax,
melt it and add 2 percent by weight of the fungicide. If it is a
liquid polish merely add the powdered fungicide to the liquid
polish and shake the bottle before applying the polish. The
soles may also be treated to prevent mildew growth. It is ques-
tionable, however, whether the inside of the shoe should be
treated with a fungicide since mildew does not harm the shoe,
and the perspiring foot may be highly sensitive to chemical
Cellulose, lignin, and the soluble matter of wood provide a
source of nutrients for insects and fungi. Wood is, therefore,
highly vulnerable to the
ravages of insects such
as termites, powder post
beetles and carpenter
ants, and to attack by the
fungi. Preservation must
take into account both in-
t o The fungi that rot or
Sldecay wood are highly de-
veloped fungi belonging
to the class known as
Bas.diomycetes. These are
recognized by the highly
developed spore bearing
bodies that may take the
1 form of toadstools or
brackets which are often
seen growing on the side
of tree stumps or rotting
logs (Fig. 12). The rot-
fungi are of two main
groups--the white rots
and the brown rots. The
white rots attack mainly
the lignin of the wood
leaving cellulose in pockets
Fig. 12.-Log showing brackets, the or streaks separated by
spore bearing bodies of wood destroying areas
fungi. The mycelium is inside the wood. of firm wood. The
brown rots prefer the cel-
lulose of the wood and leave a brownish residue that can be read-
ily crumbled into powder. Brown rots frequently cause decay in
building timbers. The common dry rot is a brown rot. Dry rot
can attack wood which is low in moisture because it is able to
transport water through its mycelium for several feet to the
Part of the wood that is being attacked. Lower types of fungi
grow on the surface of fresh lumber and produce colored sap
stains. These are superficial, however, and may be removed
by planing or scraping the surface of the wood. The stain fungi
do not decay the wood.
A great number of preservative materials have been used
to check the destruction of wood by fungi and insects. Among
them are creosote, zinc chloride, mercuric chloride, sodium
fluoride, copper salts, arsenic salts and phenol derivatives. Many
of these preservatives are mixed and used in proprietary
The standard wood preservative for the last 100 years has
been coal-tar creosote. The creosotes from wood-tar and water-
gas tar have also been used in wood preservation, but coal-tar
creosote has been available in the greatest quantity and at a low
cost. Coal-tar creosote is an oily black material resulting from
the high-temperature carbonization of coal. It is not a single
chemical substance, but is a mixture comprised of several hun-
dred compounds. Largely, these are tar acids, tar bases, and aro-
matic hydro-carbons. The tar acids, mostly phenolic compounds,
usually comprise no more than five per cent of the creosote, but
are the more potent fungicidal constituents. Creosote, as well as
being fungicidal, is insect repellent, insecticidal, water resistant,
and low in volatility. It has an objectionable odor. The oily nature
of creosote aids in its penetrating power. In commercial oper-
ations wood preservatives are forced into the wood under pres-
sure thus achieving deep penetration. This is the best method
for applying wood preservatives; however, it requires elaborate
equipment and therefore is not practical for the average in-
dividual who desires to apply the preservative himself. This
bulletin will discuss methods of application such as brushing
and spraying which involve no special equipment. It should
be borne in mind, however, that surface applications have their
limitations, for when wood checks or chips, the untreated sub-
surface wood is exposed, providing paths of entry for wood-
destroying agents. Brushing or spraying treatments of creo-
sotes are said to add from one to three years to the life of treated
poles or posts (28).
In the brushing or spraying applications first heat the
Zinc Chloride Treatsent
creosote to 150-2000F. A special creosote can be obtained which
is easily brushed on when cold; however, better penetration is
always obtained when the oily material is hot. Care should be
taken when using the hot creosote as it burns the skin. The
hot preservative should be applied liberally by flooding the sur-
face of the wood and allowing the oil to soak in. Do not spread
in a thin coat as with paint. Be sure all checks and openings are
filled with creosote. When the first.coat has dried, it is advis-
able to apply a second coat. Only dry wood can be treated since
the oil will not penetrate into wet or unseasoned wood.
Dipping the wood into the hot creosote is preferable to brush-
ing or spraying since better coverage is assured. Dipping may
add 2 to 4 years to the life of the wood. The dipping time should
be as long as practical since penetration increases with time.
Bath treatments for long periods, called steeping, permit effec-
tive penetration of the preservative. Dipping generally refers
to a bath of a few minutes duration while steeping may take
place over a few weeks. Penetration may be improved in
steeped wood by drilling holes into the center or through the
wood before putting it into the bath.
Painting creosoted wood is best accomplished by first giving
the timber a 2 or 3 week drying period after creosoting and
then applying 2 coats of aluminum paint. If a dark color is
desired, an over-coat of dark paint may be applied. Light-
colored over-coats are likely to be discolored by the creosote
even though the aluminum paint is not
The use of zinc chloride as a wood preservative has been
second only to creosote in the quantities used. Its advantages
are: (1) It is inexpensive; (2) It can be applied in water solu-
tion; (3) It can be applied to unseasoned timber; (4) It leaves
wood clean and paintable; (5) It has no odor. The disadvant-
ages are: (1) Being water soluble, it leaches out of timber that
becomes wet; (2) Application in water solution wets the wood
and necessitates subsequent drying before using for certain
Zinc chloride may be applied in the same manner as creosote
except that the solution is not heated. Dipping or steeping are
greatly preferable to brushing or spraying as methods of appli-
cation. For seasoned lumber use a 5 per cent aqueous solution
of zinc chloride with a wetting agent to aid penetration of the
liquid. For "green" timber, a 10 per cent solution is used:
Copper Naphthenate Treatment
For Seasoned Timber:
Zinc Chloride ........ ....... ...... 7 ounces
Aerosol O. T. (10%) ......................... 0.5 ounces
W ater .................................................... 1 gallon
For Unseasoned Timber:
Zinc Chloride ....................... ............... ounces
Aerosol O. T. (10%) .............................. 0.5 ounces
W ater ........................................................ 1 gallon
For treating unseasoned timber a water-soluble preservative
is essential because oils cannot penetrate the wet wood. The
dissolved zinc chloride diffuses into the wet wood and is diluted
by the water in the wood. Therefore, the original concentration
must be greater in order to get sufficient preservative into the
Painting wood preserved with zinc chloride presents no par-
ticular problems. For outside work, the paint will last longer
if the wood is first treated with a priming coat of aluminum
paint. Two outer coats of white paint are then generally neces-
sary to hide the aluminum color.
Chromated zinc chloride, which is 80 percent zinc chloride
and 20 percent sodium dichromate, may be used in place of zinc
chloride. Some claim it to be superior to zinc chloride. The
method of application is the same.
Preliminary tests in Trinidad (29) have shown that this
relatively new wood preservative has great promise. Pieces of
treated and untreated wood were exposed to fungus and termite
destruction in a tropical "timber graveyard". After twenty
months the treated wood was said to be perfectly sound, while
the untreated pieces were completely destroyed in six months.
Copper naphthenate has a pleasant greenish color, a slight
petroleum-like odor, is resistant to leaching with water, and is
not expensive. It dissolves in cheap oil solvents like kerosene,
naphtha, and fuel oil and is not dangerous to handle. The appli-
cation is like that for creosote. A solution of approximately 26
percent copper naphthenate (8 percent copper) has been found
Copper naphthenate (8 percent copper) 2.5 pounds
Petroleum solvent ...................................... 7.5 pounds (approximately
The solvent may be fuel oil, kerosene, naphtha, or a mixture
of 2 parts of waste crank-case oil to 1 part kerosene.
, i i 1 "
Fig. 13.-Wood samples treated as follows:
Sodium pentachlorophenate 2% percent solution
Sodium pentachlorophenate 5 percent solution
Sodium pentachlorophenate 2 percent, plus borax 2 percent
Sodium pentachlorophenate 1 percent, plus borax 2 percent
Leached 4 hours in water after treatment
Leached 4 hours in water after treatment
Not leached after treatment
Not leached after treatment
4 weeks exposure
4 weeks exposure
8 weeks exposure
8 weeks exposure
Dark spots in center of each panel is daub of paint.
C^. ,. n.mn... Plant Tnd lstrv USDA)
Lumber Stain Control
Since copper naphthenate is oil-soluble, it will bleed through
paint. The following composition of preservative is said to
prevent bleeding (30):
Copper naphthenate (8 percent copper)...... pounds
Linseed oil ............................................... 8.8 pounds (0.5 gallon)
Cobalt drier ............. ...................... 1 ounce
Naphtha .......................................................... 3.8 pounds (0.5 gallon)
One coat of dark-colored paint or two coats of white paint
are needed to cover the greenish copper naphthenate. The paint
can be put on 48 hours following the preservative treatment.
To prevent sap stain and surface mold, lumber is dipped into
a fungicidal bath. The water-soluble sodium salts of tetra-
chlorophenol or pentachlorophenol have served this purpose.
The lumber can be dipped for ten seconds into a bath of 3 to 5
percent of the fungicide in water. For a 5 percent solution, dis-
solve 7 ounces in a gallon of water. These fungicides are toxic
and should be handled carefully. The Division of Forest Pa-
thology of the U. S. Department of Agriculture reports the fol-
lowing solution effective (Fig. 13):
Sodium Pentachlorophenate .......... 3 ounces
Borax ..... ..................... .......................... .. 3 ounces
W ater ......................... .......... .......... ... gallon
MILDEW ON BOOKS
Book covers suffer both from mildew and insect damage.
The mildew may be superficial and easily wiped off or the mold
may exude acids which permanently stain the dye in the book-
cloth. Starch-filled book covers offer a tempting feeding ground
for molds and roaches. Roach damage is much more severe than
mildew since the insects chew deep into the book cover leaving
it marred and unsightly.
Libraries often shellac all book covers to prevent the harm
done by insects and fungi. While this treatment does not pre
vent mold growth, the mold that does occur may be easily re-
moved and does not stain the book cover. When the book is
handled the perspiration of the hands transfers sufficient or-
ganic materials for luxuriant mold growth (Fig. 14). To pre-
vent mold, two alternatives are possible. The first is to wipe
the book cover with a cloth wet with a fungicidal solution. The
second is to incorporate a suitable fungicide in a shellac or
Mildew on Books
lacquer. The second method is preferred because it gives the
added protection against insects.
For the fungicidal solution either salicylanilide or dihydroxy-
dichloro-diphenylmethane are suitable because of their low
toxicity and lack of objectionable color and odor. A concentra-
tion of 1.5 ounces of the chemical di ,solved in a gallon of rubbing
alcohol may be employed.
For the second method, the same fungicides are recom-
mended. They may be simply incorporated with shellac. which
is also soluble in alcohol. To prepare a preservative book shellac
the following formula can be used:
W hite shellac ...... ............................ 2 pounds
Fungicide ............ ................................ 1.5 ounces
A alcohol .................................... ...... .... 1 gallon
The shellac may take a day to go into solution. Warming
slightly will hurry the process, but do not boil the alcohol. A
prepared white shellac may be bought from a paint dealer if
desired. It should be diluted with approximately an equal
volume of alcohol to give the desired consistency, and 1.5 ounces
of fungicide added per gallon of finished shellac solution.
Fig. 14.-Mildew appears where book is handled. Note edges and back
of book cover.
Mold Problems in the Baking Industry
MOLD CONTROL IN BAKERIES
The "bread mold" fungi are visitors during the hot summer
months. While these fungi do not make the bread harmful to
*eat, they nevertheless make it inedible from an aesthetic stand-
point (Fig. 15). The losses in baked products resulting from
mold runs into millions of dollars yearly.
The bread molds belong to the genera Rhizopus, Penicillium
and Asperigillus that are also found growing on the surface of
leather, paints, etc. Because of its starch and sugars, its high
moisture content, and its spongy structure bread is an ideal
medium for mold growth. The mold mycelia grow on the crust
and through the bread giving rise to the black, green and yellow
colored spores (Fig. 16). Control of bread mold is best accom-
plished before or directly following the baking process. There
Fig. 15.-Moldy bread may not be harmful to eat but it is not
PrereHt Mold Growth Before it Starts
is little that can be done once the bread has begun to mold,
except to cut away the infected part.
Sanitation in the bakery or kitchen is the first step in com-
batting bread mold. Walls should be kept clean and free of
mold, especially damp dough rooms and proofing boxes. Spore-
carrying dust should be kept at a minimum by proper sanitation
and utilizing washed air, if possible. Wrapping materials should
be kept clean and away from flour and dust. Germicidal ultra-
violet lamps are used in some bakeries to help sterilize the air
and to prevent contamination of the bread during the slicing and
wrapping processes (Fig. 5).
It has often been said that old fashioned homemade bread
was more resistant to mold than modern commercially-produced
bread. This is probably true because the old-fashioned bread
was baked to produce a hard dried-oat crust which was fairly
resistant to mold attack. After bread has been baked it is ad-
visable to allow it to become cool before wrapping, otherwise
the moisture from the center condenses on the outside of the
loaf, making the crust moist and soft and well suited for mold
In recent years, non-toxic mold inhibitors have been used
very effectively by incorporating them in the dough. The salts
of propionic acid, which are naturally occurring in Swiss cheese
making it resistant to molds, are mixed with the flour and slow
up the growth of molds past the normal fresh life of the bread.
Fig. 16.-A close-up view of bread mold showing the black spore heads.
Each spore head is covered with spores. (Courtesy of E I. Dupont de
Nemours & Co.)
The propionates have a cheese-like odor and taste, but in the
small quantities employed as bread mold inhibitors, they do not
affect the taste or texture of the bread. The propionates are
extensively used in commercial baking today for bread, cakes
and pies. Sodium propionate is used for bread and cake doughs
while calcium propionate is intended for use in bread doughs
The propionates are also effective in combatting another
source of spoilage of bread known as ropinesss". "Ropiness"
is recognized as a pasty, stringy, bad smelling mass in bread
which has undergone this type of spoilage. It is not caused by
mold, but is of bacterial origin.
The following instructions on the use of propionates (S1, 32)
employ quantities used in bakeries. For home use the quantity
of propionates can be reduced in proportion to the amount of
flour used. Under ordinary conditions, the propionates retard
the appearance of mold on white bread as follows:
2.5 ounces of propionate per 100 lbs. flour will add 1 day
3.5 ounces of propionate per 100 lbs. flour will add 2 to 3 days
4 ounces of propionate per 100 lbs. flour will add 4 to 5 days
5.5 ounces of propionate per 100 lbs. flour will add 6 to 7 days
For average conditions the recommended amount to be used are:
White bread 2.5 to 3.5 ounces per 100 lbs. flour
Dark bread 4 to 5 ounces per 100 lbs. flour
For extreme conditions favoring mold growth, use:
White bread 35 to 5 ounces per 100 lbs. flour
Dark bread 5 to 6 ounces per 100 lbs. flour
For cakes and pies the following amount are used:
Devils Food Cake 7 ounces per 100 Ibs. of total batter
Chocolate cake 5 to 7 ounces per 100 lbs. of batter
Pound cake 5 ounces per 100 lbs. of total batter
Angel Food 1.5 to 2.5 ounces per 100 lbs. of total batter
Pie Filler* 3 ounces per 100 lbs. of mix
Pie crust 3 ounces per 100 lbs. of dough
*The propionates are not recommended for cream-filled pies.
PROPERTIES OF SOME USEFUL INDUSTRIAL
Below are listed a number of fungicides that are industrially
useful. The list is by no means complete nor are the properties
of any fungicide given in detail, for such treatment would be
too lengthy for this bulletin. Each compound will be considered
from the standpoint of its chemical type, its physical character-
istics, its toxicity to human beings and its applications.
Many chemicals may be obtained through the local druggist,
insecticide and fungicide dealer, chemical supply store, hard-
ware or paint dealer. For those products not in stock, the local
dealer may be able to obtain them from his jobber, wholesaler,
or directly from the manufacturer. For any further informa-
tion on obtaining chemicals or the treatments discussed in this
bulletin write to this Station. Address The Director, Engineer-
ing and Industrial Experiment Station, University of Florida,
Copper sulfate is a blue crystalline solid, odorless and soluble
in water. It is highly effective against cellulose-decomposing
fungi, but low in toxicity to surface-growing molds. It is poison-
ous if taken internally. Since it is also effective as an algaecide
it is used in swimming pools for this purpose. It has been used
in wood preservation, but has the disadvantage of attacking
iron or steel with which it may come in contact. Copper sulfate
is also known as blue vitriol or blue stone.
Copper Naphthenate is a greenish waxy solid with a petro-
leum-like odor. It is soluble in petroleum oil and petroleum
solvents such as benzene, naphtha, and kerosene, but insoluble
in water. It is relatively safe to handle. The use of copper
naphthenate in fabric and wood preservation has been discussed.
(See pages 22a, 33). Typical proprietary products are "Nuodex
Copper" and "Triple A Copper Naphthenate Wood Preserver",
and "Nopco 1049".
Copper Oleate, Copper Reinate, Copper TaIlate
These compounds are oil soluble, water-insoluble copper
soaps. They are also soluble in some oil solvents like ether.
Copper oleate has little odor while the resinate and talate have
characteristic aromatic odors. They are all blue, waxy solids.
These compounds are used as copper naphenate is used, although
they are not as strong fungicides. They are safe to handle.
It is a solid with a yellow-green color and practically no odor.
As it is insoluble in water and all common solvents, it is applied
by the two-bath process as described. (See page 22a). The com-
pound is very stable as a fabric protectant. It is not a skin
irritant and is low in toxicity.
This purple-colored compound combines the fungicidal prop-
erties of pentachlorophenol with those of copper. It is highly
effective as a fabric protectant and evidence indicates that it
also repels termites. It is applied by a two-bath process: the
first bath consists of sodium pentachlorophenate, while the
second bath is a soluble copper salt as cooper sulfate.
Copper Ammonium Hydroxide and Copper Ammonium Fluoride
The cuprammonium compounds are sold as blue, aqueous
solutions or sludges. They have an odor of ammonia which is
lost after drying. The process of application is as described
(page 22a) for copper ammonium fluoride. These compounds are
not highly fungicidal to surface-growing fungi. A typical pro-
prietary product employing cuprammonium hydroxide is "Mil-
dewproof Extra W-1481B". Typical proprietary products em-
ploying cuprammonium fluoride are "Mildewproof W-1478",
"Protela SB", and "Protela Powder".
Zinc naphthenate is a colorless, plastic solid with a petro-
leum-like odor. It is only about half as fungicidal as copper
naphthenate and therefore has to be used in twice the amounts
of copper naphthenate for equivalent protection. It is insoluble
in water and soluble in petroleum oils and solvents. The tqxicity
is low. Typical proprietary products are "Nuodex Zinc" and
Zinc Dimethyl Dithiocarbamate
This compound previously used as a rubber accelerator, was
found to be toxic to fungi. It is a white, odorless solid that is
insoluble in water and the common organic solvents. Exposure
to strong sunlight, high temperatures, and acids may decompose
this compound. In concentrations up to 1 percent in fabric, it
is not a skin irritant. It is recommended as a fabric preserva-
tive under conditions of slight outdoor exposure; also for lac-
quers, varnishes, and waxes, where it will not be exposed to
prolonged ultraviolet light. Typical proprietary products are
"Milban" and "Methyl Zimate".
Zinc oxide is a white odorless powder which is used as a
toxic pigment in paints. It is not soluble in water or organic
solvents and is not irritating to the skin.
Zinc chloride is a white, odorless, deliquescent solid. It is
soluble in water and highly acid, therefore it should be handled
carefully to avoid contact with the skin. Its use as a wood
preservative has already been discussed. (See page 32).
Known also as corrosive sublimate and bichloride of mer-
cury, this compound is very toxic, both to fungi and to man.
It is a white, odorless crystalline solid, soluble in water and in
alcohol. Its use in paints and as a general disinfectant and
germicide have been discussed. (See page 26). Mercuric
chloride should be used with great care because of its poisonous
and skin-irritating properties.
Mercurous chloride, or calomel, is a white, odorless powder
which is insoluble in water. Because it is so insoluble, it is
much less toxic as a fungicide and as a human poison than cor-
rosive sublimate. It can be used as a toxic material in paints.
(See page 27).
Mercuric naphthenate is a thick, dark amber colored liquid
with a petroleum-like odor. It is insoluble in water but soluble
in oil and petroleum solvents. Its main use is mildew-prevention
of oil paints. It is highly poisonous.
The phenylmercuric compounds are organic compounds which
are highly toxic to fungi but are not as toxic to human beings
as the soluble inorganic mercury salts. As with all mercury
comounds, however, great care should be taken in using these
compounds. The phenylmercurics may redden or blister the
skin, especially with persons sensitive to mercury. The mer-
curials are very toxic to most species of fungi.
This is a brownish paste with an oil-like odor. It is soluble
in alcohol and ethylene dichloride, but insoluble in water. It is
used in paints and for textile and wood preservation. It is very
poisonous. Typical proprietary products are "Fungicide IN-2555"
and "Fungicide IN-5499". The latter is dispersible in water.
This white, odorless, crystalline solid is soluble in alcohol,
but only slightly soluble in water. It has been used for a fabric
preservative, as a germicide in the paper industry, in paints,
in tanning, and for the prevention of sap stain. The acetate
is the parent compound of the phenymercury series and it is
the least expensive. It is very poisonous. Typical proprietary
products are "Mersolite-8" and "Merphenyl Acetate".
Similar to phenylmercuric acetate, this compound is a white,
odorless solid. It is less soluble in water and more soluble in
benzene. Its uses are similar to those of the acetate. It is very
poisonous. A typical proprietary product is "Mersolite-19".
Other phenylmercuric compounds include: Phenylmercuric
Chloride, ("Mersolite-2"), Phenylmercuric Nitrate, Phenylmer-
curie Benzoate, Phenylmercuric Borate, ("Merolite-90"),
Phenylmercuric Hydroxide, ("Mersolite-l"), and Phenylmercuric
Triethanol Ammonium Lactate, ("Puratized N5-X"). They are
all very poisonous.
Pyridylmercuric Chloride, Pyridyhnercuric Stearate,
and Pyridylmercuric Acetate ("Pyridose")
These are white solid organic mercurials. The chloride and
stearate are insoluble in water while the acetate is very soluble
in water. Because of its water solubility, the acetate is a much
more active skin irritant than the other organic mercurials. It
is effective in industrial slime control. The chloride can be ap-
plied to fabrics by the two-bath process, while the stearate dis-
solves in turpentine. These compounds are suggested for use
in fabrics, rubber, paper, leather, paint, cork, lacquer, and wax
fungus-proofing. They are all very poisonous.
COMPOUNDS OF OTHER HEAVY METALS
The salts of lead, cadmium, silver, and thallium have been
used as fungicides. Lead pentachlorophenate applied to textiles
and rope by the two-bath process is highly protective. Cad-
mium salts have been found to be too poisonous for their limited
fungicidal properties. Silver and thallium salts are highly
effective fungicides, but are too expensive for industrial use.
Thallium, in addition, is extremely poisonous.
The phenolics have received the greatest attention of the
non-metallic organic fungicides. They are potent toxic agents
to a large number of fungi and are not as poisonous as many
of the heavy metal fungicides.
Phenol, or carbolic acid, was introduced as a germicide in
surgery by Dr. Joseph Lister in 1870. Since that time it has
been a standard germicidal chemical. However, phenol is very
poisonous if taken internally and also very active on the skin.
Many of the chemical derivatives of phenol have been found to be
much safer to handle and are also more potent as fungicides.
Phenol is a white crystalline mass that may be pink if not pure.
It picks up water from the air and liquefies. It is soluble in
water and many organic solvents.
o-Phenylphenol is a white to pinkish solid with a mildly anti-
septic odor. It is very slightly soluble in water, but highly
soluble in alcohols, ether, benzene and acetone. It will dissolve
in alkaline aqueous solutions. It is not a skin irritant when
used up to 1.75 percent of the weight of cotton duck. Uses in
casein paints, leather finishes, cosmetics, sizing materials and
as a household disinfectant have been suggested for this com-
pound. The sodium salt of this compound, as in the case of the
other phenols, is soluble in water. Weathering will remove this
compound from fabrics. A typical proprietary product is "Dowi-
This is a clear, light-colored liquid with an antiseptic odor.
It is a good fungicide, but is slightly irritating to the skin.
While only very slightly soluble in water, it is miscible in all
proportions with most organic solvents. It forms a water-
soluble sodium salt. Uses suggested are for preventing dry rot
and termite attack of wood and as a fabric preservative. Typi-
cal proprietary products are "Dowicide 3" and "Dowicide 4".
Tetrachlorophenol is a tan colored solid with a strong anti-
septic odor. Insoluble in water, it is soluble in most common
organic solvents. The sodium salt dissolves in water. One per-
cent of the compound on the fabric is not irritating to the skin.
The dust of this compound should not be inhaled as it is irritat-
ing to the nasal membranes. Tetrachlorophenol is used in the
manufacture of rot-proof and termite-proof insulation board and
also as a mildew-proofing agent for water paints. A typical
proprietary product is "Dowicide 6".
This compound is one of the most potent and useful of the
phenolic fungicides. It is a dark grayish solid with a definite
phenolic odor. It is insoluble in water, but dissolves in alcohol
and many organic solvents. Pentachlorophenol and its water-
soluble sodium salt are effective against a great number of
fungi. It is irritating to the skin and should be handled with
care. Its uses include wood preservation, prevention of sap stain
of lumber, fabric protection, and mildew-proofing of paint. It
is also used as an algecide. Typical proprietary products are
"Santophen 20" and "Dowicide 7".
Known also as thyme camphor, thymol is a colorless solid
with an aromatic camphor-like odor. It is only slightly soluble
in water, but readily dissolves in alcohol, ether, and other or-
ganic solvents. It is low in toxicity. Uses are mainly where
low-toxicity fungicides are essential such as in indoor paints
for food plants. (See page 27.)
This odorless, water-insoluble, white to pinkish powder has
the advantage of being an effective fungicide although low in
toxicity. It is soluble in alcohol and lacquer solvents. Alkaline
solutions and continuous immersion in water will leach out this
fungicide. Its main uses are in mildew-proofing woolens, leather
goods and other materials not exposed to weathering. (See
pages 22a, 29, 36.) Typical proprietary products are "Shirlan
Extra" (pure chemical), "Shirlan A" (Water dispersion) and
"Shirlan D" (dispersible powder).
Like salicylanilide, this compound is low in toxicity and is a
white to tan solid with little odor. It is not soluble in water,
but dissolves in alcohol and lacquer solvents. Developed dur-
ing the war, it has given satisfactory results when tested as a
textile preservative. Other suggested uses are as disinfectant
for rubber, cosmetics and pharmaceuticals. Typical proprietary
products are "Preventol GD" and "Fungicide G-4".
Tetrabromo-o-Cresol, (Fungicide 242), p-Chloro-m-Cresol,
p-Nitrophenol and p-Chloro-m-Xylenol
These are phenolic fungicides which have been suggested
for mildew-proofing of leather and textiles.
QUATERNARY AMMONIUM COMPOUNDS
This product is a yellowish liquid with very little odor. It
is soluble in water and alcohol. While fairly effective as a fungi-
cide, it is very low in toxicity to humans and is not a skin irritant.
Its uses are as a household disinfectant, as a dairy disinfectant,
sterile storage of medical instruments, etc. Typical proprietary
products are "Zephiran" and "Onyx B.T.C."
This-compound combines the properties of the quaternary
ammonium compounds with that of pentachlorophenol. De-
veloped for use as a fabric preservative, this compound is un-
suited for outdoor exposure since it is not stable to ultraviolet
light. It is soluble in water, but is not leached from fabric
because it is adsorbed into the textile fibers. It is a strong
fungicide and has a slight, characteristic odor. It has been
found useful for treating thread and yarns to prevent rotting.
A typical proprietary product is "Fungicide H-3258".
N(Acyl Colamino Formyl-Methyl) Pryidinium Chloride
As well as having fungicidal and germicidal action, some of
the quaternary ammonium compounds are very efficient deter-
gents. This compound is an excellent soap substitute, which
disinfects and cleans at the same time. It cannot be used with
soaps or alkaline cleansers. Since it is low in toxicity it may
be used as a disinfectant for food plants, for equipment used
in food processing, for ceilings, and walls, etc. It may be
diluted as desired with water. A typical proprietary product
Formaldehyde is a well known disinfectant. It is a gas with
a sweetish, unpleasant odor and is irritating to the membranes
of the nose and eyes. Commercially it is used as formalin, a
37% solution of formaldehyde in water. The volatility and
odor of formaldehyde restrict its usefulness; however, it finds
wide application as a fumigant and disinfectant.
While borax and boric acid are not strongly fungicidal, they
still find use in some industries because they are not very
harmful to man. For example, they are used as a wash for
citrus fruit to deter rot organisms. The compounds are white,
odorless, water-soluble solids.
Biphenyl has found use recently as a fungus inhibitor in the
shipment of citrus fruit to market. The biphenyl, a volatile,
white solid with a camphor-like odor, is applied to the paper
bags or wrappers in which the fruit is shipped. Biphenyl is
not a powerful fungus inhibitor, but is harmless to humans in
the manner in which it is used.
Propionic acid and the sodium and calcium salts are useful
mold-inhibiting agents because they may be taken internally
in small quantities without being harmful. As such they may
be incorporated in foodstuffs such as baked goods and dairy
products. (See page 38.) Propionic acid incorporated in wax,
makes a mold inhibiting wrapper for butter, cheese, and other
products not affected by the slight cheese-like odor of propionic
acid. Propionic acid is a colorless liquid while the salts are
white solid. They all dissolve in water.
Benzoate of Soda
Benzoate of soda is a common food preservative. It is the
sodium salt of benzoic acid and is a relatively effective mold in-
hibitor. It is low enough in toxicity to be permitted in foods
to the extent of 0.5 per cent. In nature, benzoic acid is found
in cranberries. Both the water-insoluble benzoic acid and water-
soluble benzoate are white crystalline solids.
This relatively harmless compound, a sulphur-bearing equiva-
lent of the common urea, has been found effective as a mold in-
hibitor toward several molds common to citrus fruit. Its com-
mercial application to prevent stem end rot is under investigation.
1. GALLOWAY, L. D. "The Moisture Requirements of Mold Fungi with
Special Reference to Mildew in Textiles". J. Textile Institute 26,
2. WAKSMAN, S. A. "Fungi and Tropical Deterioration", 3rd Ed.
O.S.R.D. Report No. 4101 (1944).
3. SHANOR, L. "Fungus-Proofing of Textiles and Cordage for Use in
Tropical Service", O.S.R.D. Report No. 4513 (1945).
4. BARCHOORN, E. S. "Studies of the Deterioration of Textiles Under
Tropical Conditions in the Canal Zone", O.S.RD. Report No. 4807
5. MONSANTO CHEMICAL COMPANY. "Copper 8-Quinolinolate and Its Use
as a Textile Preservative", Technical Report O-D-200.
6. NUODEX PRODUCTS COMPANY. "Nuodex Service Data".
7. TWEEDIE, A. S. and BAYLEY, C. H. "The Preservation of Cordage",
American Dyestuff Reporter 33, 373 (1944).
8. ALBI CHEMICAL CORPORATION.
9. AMERICAN CYANAMID COMPANY.
GENERAL DYESTUFF CORP.
i1. NEILSON, A. W. and CHARD, F. H. "Cutaneous Reactions of Some
Pyridylmercuric Salts", Mallinkrodt Chemical Works (1944).
12. CHEMICAL WARFARE SERVICE DEVELOPMENT LABORATORY, Mass. Insti-
tute Technology. "Comparative Evaluation of Commercial Fungi-
cides." Tropical Deterioration Information Center. Miscellaneous
Report No. 12.
13. FARGHER, R. G., GALLOWAY, L. D., and PROBERT, M. E., The British
Cotton Industry Research Association, English Patent 328,579
14. BENNET, H. "Formulas for Profit", World Publishing Company (1944).
15. "Removal of Mildew", Canadian Textile J. 60 39 (19.3).
16. WEISE, K. "The Breakdown of Linseed Oil Paints by Fungi", Farben-
Zeitung 39 412, 444 (1934).
17. GARDNER, H. A., HART, L. P., and SWARD, G. G. "Mildew Prevention
on Painted Surfaces," Circular 448 National Paint, Varnish and
18. SLAVIN, S. B. "Influence of Zinc Oxide on Paint Molds", Industrial
and Engineering Chemistry 36 336 (1944).
19. STOCK, E. "Mold Resistant Paints", Farben-Zeitung 42 283 (1942).
20. WELLMAN, R. H., and MCCALLAM, S. E. A. "Fungus Resistance of
Plastics", O.S.R.D. Report No. 5683 (1945).
21. BROWN, A. E. "The Problem of Fungal Growth of Synthetic Resins,
Plastics, and Plasticizers", O.S.R.D. Report No. 6067 (1945).
22. GARbNER, H. A., et al., National Paint, Varnish and Laquer Assn.,
Scientific Section Circulars 335, 442, 448, 464, 475, 526, 558, 574,
579 and 589.
23. GARDNER, H. A. "Painting Problems in the South", Southern Feder-
ation Associates of Atlanta, Georgia (1936).
24. KAGANY, J. R., CHARLES, A. M., ABRAMS, E., and TENER, R. F. "Ef-
fects of Mildew on Vegetable Tanned Strap Leather", J. American
Leather Chemists Assn. 41, 198 (1946).
25. LOLLAR, R. M. "Report on a Study and the Development of a Mold
Resistant Treatment for Leather", J. American Leather Chemists
Assn. 39 18 (1944).
26. LOLLAR, R. M. "Report on Mold Resistant Treatments for Leather",
J. American Leather Chemists Assn. 39 179 (1944).
27. GREENE, H. S., and LOLLAR, R. M. "Report on Preservatives in Army
Dubbings", J. American Leather Chemists Assn. 39 209 (1944).
28. HUNT, G. M., and GARRATT, G. A. "Wood Preservation", p. 183.
McGraw-Hill Book Company (1938).
29. BERRY, A. V. G., and CARTER, J. C. "Preliminary Report on Trials
of Copper Naphthenates and Mercuric Naphthenates as Wood
Preservatives", Empire Forestry J. 20 (1941).
30. BARTzwrr, A. E. "The Preservation of Wood with Nuodex Copper",
Nuodex Products Co. (1944).
31. MILLER, F. W., Jr. "The Mold and Rope Problem in the Baking In-
dustry", Bakers Digest (June, 1943).
32. E. I. Dupont de Nemours & Company "Mycoban Mold and Rope In-
hibitor Bakery Instructions".
Much of the information in this bulletin has been gathered from
various sources. To our best knowledge the methods are reliable and
accurate, and therefore are presented here. However, because the Engi-
neering and Industrial Experiment Station has no control over the condi-
tions of use of these methods, it cannot guarantee any individual results
obtained and the Station must disclaim any liability incurred in connection
with the use of these data and suggestions. Furthermore, nothing herein
shall be construed as a recommendation to use any product in conflict with
existing patents covering any material or its use.
PUBLICATIONS OF THE FLORIDA
ENGINEERING AND INDUSTRIAL EXPERIMENT STATION
Address all requests
to: The Director, Florida Engineering and Industrial Experi-
ment Station, University of Florida, Gainesville, Florida.
No. 1 "The Mapping Situation in Florida", by William L.
No. 2 "The Electrical Industry in Florida", by John W. Wilson.
No. 3 "The Locating of Tropical Storms by Means of Asso-
ciated Static", by Joseph Weil and Wayne Mason.
No. 4 "Study of Reach Conditions at Daytona Beach, Florida,
and Vicinity", by W. W. Fineren.
No. 5 "Climatic Data for the Design and Operation of Air
Conditioning Systems in Florida", by N. C. Ebaugh
and S. P. Goethe.
No. 6 "On Static Emanating from Six Tropical Storms and its
Use in Locating the Position of the Disturbance", by
S. P. Sashoff and Joseph Weil.
No. 7 "Lime Rock Concrete-Part 1", by Harry H. Houston
and Ralph A. Morgen.
No. 8 "An Industrial Survey of Hides and Skins in Florida",
by William D. May.
No. 9 "Studies on Intermittent Sand Filtration-Part I", by
D. L. Emerson, Jr.
No. 10 "Florida Spray Gun for Pine Tree Gum Stimulation",
by Norman Bourke and K. W. Dorman.
No. 11 "Developments of Ceramic Compositions Suitable for
the Production of Porcelain Type Artware", by B. W.
No. 12 "Mold and Mildew Control for Industry and the Home",
by S. S. Block.
TECHNICAL PAPER SERIES
No. 1 Heats of Solution of the System Sulfur Trioxide and
Water, by Ralph A. Morgen.
No. 2 The Useful Life of Pyro-Meta and Tetraphosphate, by
Ralph A. Morgen and Robert L. Swoope.
No. 3 Florida Lime Rock as an Admixture in Mortar and Con-
crete, by Harry H. Houston and Ralph A. Morgen.
No. 4 Country Hides and Skins, by William D. May.
No. 5 Empirical Correction for Compressibility Factor and Ac-
tivity Coefficient Curves, by R. A. Morgen and J. H.
No. 6 Crate Clo.ing Device, by William T. Tiffin.
No. 7 The System Sodium Acetate-Sodium Hydroxide-Water,
by R. A. Morgen and R. D. Walker, Jr.
No. 8 Patent Policies for Sponsored Research, by Ralph A.
No. 9 Conservation of Municipal Water Supplies in Air Con-
ditioning Systems, by N. C. Ebaugh.
No. 10 Florida Scrub Oak-New Source of Vegetable Tannin,
by H. N. Calderwood and William D. May.
No. 11 Protein Feed from Sulphite Waste Liquor, by R. D.
Walker, Jr., and R. A. Morgen.
No. 12 Effect of Moisture on Thermal Conductivity of Lime-
rock Concrete, by Mack Tyner.
No. 13 Insect Tests of Wire Screening Effectiveness, by S. S.