Wood preservatives in the 19th and early 20th centuries


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Wood preservatives in the 19th and early 20th centuries
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Brown, Lewis Jr.
Lewis Jr. Brown
College of Architecture, University of Florida
Place of Publication:
Gainesville, FL
Publication Date:


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AFA Historic Preservation document 36

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Wood Preservatives

in the

19th and Early 20th Centuries

Written and Edited by

Lewis Brown Jr.

AE 681
Fall 1976

Page 1

Since wood construction began it has been threatened by several

destructive things. Rot and fire are the two most dangerous and troublesome

maladies that wood construction faced. A third problem was that of animal

attack such as termites or marine borers. In pre nineteenth century America

wood was plentiful and was easily replaced, but as more and more trees were

felled and fewer and fewer became available it became necessary to shift

efforts toward preservation of wood before construction. Several methods

were discovered or invented during the nineteenth and early twentieth centuries.

Some of the methods were organic or natural and required no foreign agents or

machinery while others did.

The durability of wood---i.e., its power of resisting the destructive

influences of wind and weather---varies greatly, and depends as much upon

the particular kind of wood and the influences to which it is exposed as upon

the origin of the wood (timber) its age at the time of felling, and other

conditions. Beech wood and oak placed permanently under water may last

for centuries. Alder wood is very lasting and substantial under water, as

also is fir, though in a dry situation alder quickly perishes.

Pure woody fibre by itself is only very slightly affected by the destructive

influences of wind and weather. Wood may in some instances last for several

centuries and remain thououghly sound; thus, the roof of Westminster Hall

was built about a.d. 1090. Since resinous woods resist the action of damp

and moisture for a long time, they generally last a considerable time; next

in respect of durability follow such kinds of wood as are very hard and compact,

and contain at the same time some substance which---like tannic acid---to

Page 2

some extent counteracts decay. The behaviour of the several woods under

water differs greatly. Some woods are after a time converted into a pulpy

Before studying the various preservatives that help prevent wood

decay it is necessary to understand what decay really is.

S9LIP6 [( The decay of a plant body, such as wood, is not an inorganic process

like the rusting of iron or the crumbling of stone, but is due to the activities

of low forms of plant life called bacteria and fungi. Bacteria are among the

simplest of all forms of life, often consisting of but a single cell, microscopic

in size. Sometimes several such cells may be attached to each other, and so

form a thread or filament. Usually they are colorless, and multiply by the

division of the parent cell into other cells, which, in turn, divide again.

Fungi, although much more complicated than bacteria, are also low

in the scale of creation when compared with familiar flowering plants and

shrubs. They consist merely of tinythreads or hyphae, which are

collectively known as the mycelium. In many of the higher forms of fungi

the threads grow together to form compact masses of tissue. Familiar

examples of these forms are the toadstools which grow on damp, rotting

logs, and the "punks," or "brackets," on the trunks of trees in the forest.

The causes of decay in wood, however, are not these fruiting bodies

themselves. Spores, very primitive substitutes for seed, which are borne

in the countless compartments into which the under surfaces of the fruiting

bodies are sometimes divided, are produced in infinite number, and are so

Page 3

fine that they can be distinguished only by the microscope. When seen in

bulk they appear as the finest dust. Like dust, they are carried by the

wind and strike all portions of the surrounding objects. Few species of

fungi successfully attack healthy living trees, and only a comparatively

small number can attack and destroy wood. Yet the spores of some find a

lodging in dead portions of a tree or in cut timber, and, if the wood is

moist and in the right condition for the spore to grow, it germinates and

sends out a thin, filmlike white thread, which, by repeated branching,

penetrates the entire structure of the wood. These are the real agents

of decay.

This is not the only way that a fungus can enter a sound stick of

timber; for if a good stick is lying close to a rotting one, the mycelium

may grow over or through the moist ground and so reach the sound stick,

which it immediately attacks. Sometimes, too, when a tree is cut it

already has a fungus growing in its wood. If the fungus happens to be a

true parasite---that is, if it can grow only in living tissues---it will die

when the tree is felled; but if it has been accustomed to growing in the

heartwood of the tree, which is practically dead, it may continue to live

and develop even after the tree has been sawed into timber.

Wood is composed of minute cells. The chief material of the cell-

walls is a substance called cellulose, and around this there are incrusted

many different organic substances known collectively as lignin. Most

of the wood-destroying fungi attack only the lignin; others attack the

cellulose alone, while a third class destroy all parts of the wood structure.

The lignin and the cellulose are dissolved by certain substances secreted

Page 4

in the fungi, and thus serve as food for the fungus growth. In this way

the fungi can develop until they extend throughout every portion of the

timber. After a time the amount of fiber changed into food and assimilated

by the fungus causes the wood to become discolored. Discoloration may

also be produced by pigments in the fungus or secreted by it. Finally so

much of the wood fiber is eaten away or changed in composition that its

strength is greatly diminished, the texture becomes brittle and

disconnected, and the wood is said to be "rotten".

But food is not the only thing that a fungus requires for its growth

and development. It must also have heat, air, and moisture. If any one

of these is lacking the fungus cannot develop. The necessary heat is

supplied by almost every climate, and it is only in rare cases, as under

water or deep under the surface of the ground, that air can be excluded

from the timber. Of the four requirements, therefore, two are beyond

control. It is only by depriving the fungi of food or moisture that the

destruction they cause can be prevented.2

The belief prevailed, that the interfibrous and cellular system of

wood contained elements denominated sap, which according to recognized

authority was vicious, and generative of destructive fungus. 3

Since the constituents of the sap are the chief cause of the

decomposition of wood, and they should consequently be removed; many

plans were adopted. The constituents of the sap could be eliminated from

the felled tree by three methods:---

(1) By treatment with cold water, with which the wood must be

Page 5

thoroughly saturated to dissolve the constituents of the sap, which were

removed when the wood was exposed to a stream of water. It is evident

that with large timber a long time was necessary to ensure perfect


(2) By employing boiling water the sap was removed much more

quickly and efficiently. The pieces of wood were placed in an iron vessel

with water, and boiled. Large pieces of timber cound not be treated in

this manner, but were immersed in a cistern in which the fluid was

heated by means of steam. According to the thickness of the wood, the

boiling occupied some six to twelve hours.

(3) By treatment with steam ( steaming of wood) ---the most

effectual method of removing the constituents of the sap, the hygroscopicity

of the wood thus treated being rendered much less, while the wood is far

more fitted to resist the effects of weather. The apparatus employed in

carrying out the method consisted of a boiler for the generation of steam,

and a cistern or steam chamber for the reception of the wood, this

chamber being constructed of masonry and cement, of boiler-plate,

or being simply a large and vary wide iron pipe. In most cases a jet of

steam was conveyed from the boiler to the steam chamber, where it penetrated

the wood, and dissolved out the constituents of the sap, which, on being

condensed, was allowed to run off. The steam was sometimes worked at

a temperature of above 100 but generally the contents of the steam chamber

were maintained at from 600 to 700. Towards the end of the operation

some oil of coal-tar is introduced into the boiler, and is consequently

carried over with the steam, impregnating the wood.

Page 6

One of the most usual and most effective means of preventing

the decomposition of wood was by producing a chemical change in the

constituents of the sap, so that fermentation could no longer be set up.

To this class belonged the well-known plan of protecting wood work that

was to be exposed to the action of the moisture of the earth by charring the

wood, either by fire or by treatment with concentrated sulphuric acid, so

that the wood was coated to a certain depth with a layer of charcoal, the

charcoal acting as an antiseptic. The charring or carbonisation of the

wood could be effected either with the help of a gas flame or the flame

from a coal fire. The apparatus of De Lapparent, invented for this

purpose, became very generally employed in 1866 at the dockyards of

Cherbourg, Pola, and Dantzic. According to another method, the wood

was impregnated throughout its whole mass with some substance that

either entered into combination with the constituents of the sap, or so

alters their properties as to prevent the setting up of decomposition.

To this class belonged the following methods, these being the only ones

that have met with more extensive use .

Kyan's preserving fluid, patented 1832, was a solution of mercuric

chloride of various degrees of concentration. The specific solution was

one pound of chloride of mercury to four gallons of water. Long

immersion of wood in the liquid in open vats or great pressure upon

both solution and wood, in large wrought iron tanks was necessary for

the complete injection of the liquid. The duribility of well kyanized

timber was proved, but the expensiviness of its operation forbade its

extensive adoption. A great objection to this method was the danger

Page 7

to which the carpenter or joiner who would later shape the wood was

exposed, the free chemicals acting upon his system through his hands,

nostrils andmouth. In the United States convicts were used to handle

wood treated by kyanization.

Burnett's fluid, patented 1840, consisted of a solution of chloride

of zinc---one pound of salt to 10 gallons of water.---Was forced into

the wood under a pressure of 150 pounds per square inch. Wood

treated with Burnett's fluid was buried in the earth for five years

without undergoing any change, while untreated wood buried in the ground

for the same amount of time was completely destroyed. Besides this

salt, copper sulphate and zinc acetate have been employed. The action

of the copper and zinc salts may be explained by considering that the

metallic oxides of the basic salt formed during seasoning separated, and

combined with the coloring matter, tannic acid and resin of the wood to

form an insoluble compound.

Bethell's method, patented 1838, consisted in treatment under strong

pressure with a mixture of creosote and carbolic acid, this mixture being

known commercially as "Gallotin". Bethell inclosed the timber and dead

oil in huge iron tanks, and subjected them to a pressure varying between

100 and 200 pounds per square inch, at a temperature of 1200 F. about

twelve hours. From eight to twelve pounds of oil were injected into

each cubic foot of wood. Lumber thus prepared was not affected by

exposure to air and water, and required no painting.

Cresote is a by product of coal tar, which was produced at most

plants for the manufacture of illuminating gas and at by product

Page 8

coke-oven plants. This tar was distilled, and during the process the

condensed vapors were run into three separate vessels and thus separated

into the light oils of coal tar or nephthas, the dead oil of coal tar or

creosote, and pitch.

In and near London wood treated by Bethell's process remained

eleven years in the earth without undergoing change; other pieces of timber

so treated were subjected to the action of the sea for four years, and were

still in good condition.

One writer said that if creosote ever failed to prevent decay, it

was because of an improper treatment, or because the oil was deficient

in carbolic acid.

Sir Robert Smirke was one of the first architects to use this process,

and when examined before a Committee on Timber, stated that this process

does not diminish the strength of the material which is operated upon. He

afterwards said, "I cannot rot creosoted timber, and I have put it to the
severest test I could apply."

Payne's method which included two patents, the first having been

taken out in 1841. Both were based on the impregnation of the wood---

first with one salt, and then with another salt, which was capable of producing

with the former a precipitate insoluble in water and in the sap of the tree.

The first solution was usually one of iron sulphate or of alum; then

followed a solution of calcium chloride or of soda. The wood to be

impregnated was placed in a vessel from which the air was exhausted,

the first solution being then admitted, and pressure subsequently applied.

Page 9

The first solution being removed, the second was admitted, and pressure

again applied. It was necessary to dry the wood partially between the two

impregnations. Payne's method, possessed, the advantage of rendering

the wood somewhat uninflammable. 8

Boucherie's Method consisted in the impregnation of the wood with

the necessary substance, in a manner similar to the natural filling of the

pores with sap; that is to say, the solution was introduced into the tree from

its roots, and was thus made to take the place of the sap in all parts of the

timber. When the tree was felled, the root end was placed in a solution

of the salt and allowed to remain for some days; at the end of the required

time the wood became completely impregnated with the salt. Occasionally

this method was employed in colouring woods, colouring matter being used

instead of, or as well as, the salt. The linden, beech, willow, elm, alder,

and pear tree could be treated in this manner. The fir, oak, ash, poplar,

and cherry tree did not, however, absorb the impregnating fluid


In a later development Boucherie used the same chemicals

( sulphate of copper, one pound of the sulphate to 12- gallons of water

or one gallon pyrolignite of iron to six gallons of water) but he enclosed

one end of the green stick in a close-fitting collar, to which was attached

an impervious bag communicating through a flexible tube with an

elevated reservoir containing the salt liquid. Hydrostatic pressure

soon expelled the sap at the opposite end of the log; and when the solution

also made its appearance the process was completed.

He found that the fluid would pass along the grain, a distance of

12 feet, under a lower pressure than is required to force it across the

Page 10

grain, three-fourths of an inch. The operation was performed upon

green timber with the greatest facility.10

Along with any study of wood preservation processes should

be a study of application-methods. For the processes previously mentioned

three main application methods were used. In the United States the pressure

process was the most common. With creosote it was known as the Bethell

process, and with zinc chlorid the name of Burnettizing was applied.

The timber to be treated was placed on iron trucks or "cylinder buggies"

and drawn by steel cables into huge horizontal cylinders, some of which

were 8 or even 9 feet in diameter and more than 150 feet long. These

were capable of withstanding high pressure, and their doors were so

arranged that, after the timber was drawn in, they could be closed and

hermetically sealed. It was the common practice in this country---a

practice which long experience in Europe, as well as in America, was

proved to be unwise---to treat the timber before it had time to dry out

in the open air. The following was the usual method. After the doors

were closed live steam was admitted into the cylinder, and a pressure of

about 20 pounds per square inch was maintained for several hours, the

exact time depending upon the individual opinion of the operator, as well

as upon the moisture content and size of the timber under treatment. In

some cases the steam pressure was allowed to go considerably above

20 pounds, but there was constant risk of injuring the strength of the

timber. When the steam was at last blown out of the cylinder, the vacuum

pumps were started and as much of the air as possible was exhausted from

the cylinder and from the wood structure. This process also continued

Page 11

for several hours. Finally, after the completion of the vacuum

period, the preservative was run into the cylinder and the pressure pumps

were started and continued until the desired amount of preservative fluid

was forced into the wood. The surplus preservative was then blown back

into the storage tanks, the timber was allowed to drip for a few minutes,

and finally the cylinder doors were opened and the treated timber was


C-LIPE f- The injection of the preservative by the open-tank process depended

upon a different principle. The wood was first thoroughly seasoned, and

much of the moisture in the cells and intercellular spaces was replaced

by air. If the timber was peeled soon after cutting, and stacked in open

piles, the time required for seasoning could be greatly lessened. The

seasoned timber, or that portion of it which was to be preserved, was

immersed in a hot bath of the preservative contained in an open iron tank.

This hot bath was continued for from one to five or six hours, depending

*e t!3 upon the timber. During this portion of the treatment the air and

moisture in the wood expand and a portion of them pass out, appearing

as little bubbles on the surface of the fluid. At the end of the hot bath,

as quick a change as possible was made from the hot to a cold preservative.

This causes a contraction of the air and moisture remaining in the wood,

and, since a portion of it had been expelled, a partial vacuum was

created which could be destroyed only by the entrance of the preservative.

Thus atmospheric pressure accomplishes that for which artificial press-

* 4 ure was needed in most of the commercial plants. Whether the open-

tank or pressure-cylinder method was the more desirable depends upon

Page 12

'5LIP eF r

the particular conditions of each case. Both methods have their

particular uses and neither could always be wholly substituted for

the other.

The Brush Method.---A less efficient but cheaper treatment

could be secured by painting the surface of the timber with at least

two coats of hot creosote or some similar preservative. The liquid may be

applied with an ordinary brush, but care should be taken to fill thoroughly

with the preservative all checks, knot holes, and similar defects. The liquid

could penetrate only a very short distance into the wood, but as long as

there remains an unbroken antiseptic zone around the surface, the spores

of the wood-destroying fungi cannot enter. It was especially important

in this method that the timber should be thoroughly air-dry before

treatment. Otherwise the evaporation of water from the interior of the

stick would cause checks to open up and so expose the unprotected wood

to fungous attack.

This process finds its principal use where the amount of timber

to be treated was too small to justify the erection of even a small treating

plant; where the land was so rugged, as in the building of mountain telephone

lines, that it was impracticable to transport the timber for even short

distances, or where it was necessary to restrict the cost of the

treatment to the lowest possible figure. 11

Page 13

The preservative methods aforementioned were invented and

developed during the nineteenth century. At the beginning of the

twentieth century. A new method was patented in Germany which

utilized a fixed body which became solid upon being instilled into the

pores of the wood. This substance was sulphur, the physical properties

of which offered interesting advantages, being fusible at about 115 degrees,

a temperature which the wood could support without any perceptible

change. The sulphur was applied in liquid form, and in hardening

completely filled up all the interstices of the fibrous tissue.

To protect wood by means of sulphur the following must be

observed, viz.: Sulphur was fused in a befitting receptacle, making

use of steam to avoid an excess of heat, which deteriorates the sulphur.

Into this liquid, and at a temperature of about 140 deg., were steeped the

boards which were to receive the treatment, care being taken to immerse

them completely. The foam which gathers at first, called forth by the

separation from the wood of the air and humidity it contained, disappeared

at the moment the wood thoroughly assimilates the temperature of the

bath, which was then lowered to 110 deg. At that point the sulphur

became hard and, while the air contracted itself, the sulphur penetrated

into the fibrous tissues, propelled by atmospheric pressure. The boards

were then slowly withdrawn from the bath, allowing a thin and even coat

of sulphur to form and cover the wood, as any superfluous surcharge

could be removed only with the greatest difficulties afterward. This coat

of sulphur had a vitreous appearance and formed a very tenacious crust,

excluding all tendencies to chip or break.

Page 14

The degree to which the wood was impregnated varied according

to the nature of the wood, the temperature, and the duration of the bath.

It could be gaged by the increase in weight of the boards, which amounted

to from 30 to 35 per cent where the process was conducted in an open

receptacle, and to 100 per cent if in a vacuum pan. Theoretically it

could be said that a complete fullness of the pores of the wood would

increase its weight by 200 per cent.

In numerous experiments poplar was the best wood to take the

sulphur treatment. Oak and pine wood do not admit of the process quite

so favorable, because their dry distillation began at 140 deg., which

could be proved simply by observing that while the wood was immersed

in the bath bubbles were continually rising, marking the escape of volatile

substances. Moreover, the resin blackened the sulphur. The process

in question was up to date been applied only to thin boards, but in view of

the satisfactory results the hope was entertained of its soon becoming

popular for timbers. 12

The various methods of preserving wood have been mainly

dependent upon submitting the wood to a prolonged steaming at a high

temperature, the application of pressure, or the extraction of the sap

under vacuum. But such methods were far from satisfactory, as

numerous tests and investigations carried out by the United States

government had conclusively proven. Instead of acting as a preservative,

such methods accelerated the deterioration of the wood; for although the

albuminous matter contained in the sap was coagulated, the fibers and

tissues were seriously affected, and cosequently the strength of the wood

uDPg #7

Page 15

was greatly impaired. For this reason the government had emphatically

condemned all processes dependent upon the utilization of high

pressures or vacuum.

The Powell preserving process differed entirely from any

previously exploited system, both in the material employed for

displacing the sap and in its method of application.

By this means any kind of wood could be preserved quickly,

whether it be newly-felled green timber or wood that was partly

seasoned naturally, though the best results were obtained with timber

in the green state. This peculiarity arises not from any curious affinity

for the green wood on the part of the solution, but was due to the fact

that very often partly seasoned wood had developed cracks and shakes.

The wood upon arrival at the works was immersed in a tank contained cold

water to which was added a certain percentage of sugar. This solution

was then gradually brought to the boiling point, and was maintained at

this temperature for a certain period, varying with the size and

description of wood under treatment. The latter was then withdrawn

from the tanks and was ready for drying. At the London works of the

Powell Wood Process Syndicate, which was using the patents, the

boiling was carried out in a long cylinder about eight feet in diameter.

In this chamber any sized piece of wood, ranging from small blocks to

long heavy balks, could be packed. When fully charged, the end of the

cylinder was closed and secured by hold-down bolts. The chamber was

then filled with the cold solution and slowly heated. Precisely how long the

timber should be immersed was a matter of judgment on the part of

the operator, but it had to be sufficiently long to permit the solution to

permeate to the innermost cells of the wood, and to allow them to become

Page 16

fully saturated with the sugar. The action that took place in the bath

was that as the temperature of the solution slowly increased the air in the

wood expanded a large proportion forcing itself out of the wood into the

solution, whence it escaped to the surface. Owing to the fact that the

sugar boils at a point exceeding that of water, the moisture contained in

the wood was converted into steam, and escaped in the same manner as

the released air. The moisture and air having been completely driven

out, the solution was permitted to cool, during which stage it was being

constantly absorbed by the wood. In this way every cell and interstice

became filled with sugar, and when the wood was dried, the sugar was found

to be thoroughly assimilated by its tissues. Some of the sugar was so

absorbed by the tissues that it could not be readily parted from them,

and the whole piece of timber was converted into a solid, homogeneous

mass. When a piece of Powellized wood was examined under the micro-

scope, no traces of the sugar were visible, either in the form of crystals

or drops of syrup; the sugar was evidently in some loose molecular

combination with the walls of the histological elements of the wood, as water

is in the walls of living cells.

When the wood was withdrawn from the chamber, it was transported

in wire caged trolleys to the drying room. The temperature of the air

within this apartment was at first approximately equal to that of the wood,

but it was afterward increased by the circulation of a current of hot air.

When sufficient desiccation had taken place, the temperature of the

chamber was slowly brought to equal that of the outer atmosphere.

The wood was then ready for use. During the whole process no

mechanical force of any description, either pressure or vacuum, was

Page 17

applied; this feature being one of the vital factors of the efficiency of the

system, since there was no tendency in any way to disturb the natural

fiber and tissue construction of the timber. The length of time

occupied in the treatment naturally varied according to the description

of wood and the dimensions of the pieces under treatment, hard-grained

wood of close texture, such as Jarrah or oak, occupying longer time

for complete impregnation than the common and softer woods. It

generally occupied a few days, but in special cases three to four

weeks would be required in the process. Although at the Powell

works in London a cylindrical inclosed chamber was utilized for the

boiling and saturating phases of the process, it was found that open tanks

and vats were equally serviceable and possess the additional advantage

that the method could be watched much more easily and the different

woods in the bath withdrawn with more facility at the moment when the

impregnation was complete. Little attention was required during the

boiling it being only necessary to maintain the density of the solution

at the given point; since the boiling point of the sugar solution was higher

than that of water, considerable evaporation took place, and this loss

had to be compensated by the addition of more water. It was

imperative that the wood should be kept entirely submerged to insure

a complete treatment.

Sugar as a preserving medium has the decided advantage of

being free from grit, so that it offers no more resistance to the finest

and most delicate toolwork than the unpreserved timber. Futhermore,

unlike creosote, it does not present a surface unsuseptible to paint or

polish. Indeed, in this respect it is distinctly beneficial, as the pores of

the wood are so filled up that no further stopping or priming is necessary

Page 18

for working. In the case of timber having "shakes" and cracks,

such as develop in the natural dry seasoning of wood, the sugar

acted upon these as a cement, binding the opened walls together.

Owing to the great penetrating power of the sugar solution, it

constituted an excellent vehicle for the conveyance of other substances

into the wood, such as antiseptics, and mediums for preserving the timber

against the ravages of termites, or for rendering it non-inflammable.

In such cases chemicals for fulfilling these objects were mixed with

the sugar solution before the wood was immersed, and in this manner

these preserving agents were carried with the sugar into the interior

of the wood. Powellized wood treated with chemicals for preserving

it against the white ant was employed in several countries where this

pest was encountered. 13

The problem of wood protection, of converting it from a highly

inflammable into an absolutely non-inflammable product, has floated

before the minds of generations of men rather as a vague, dreamy

proposition than as subject-matter upon which to concentrate intense

intellectual attention. Sporadic efforts void of practical utility are

historically recorded at irregular epochs, from Roman days to the

present time. The elimination of the inflammable characteristic from

wood was therefore a matter of vital consequence. And such treatment,

as shall cause it to resist disintegration from fierce heat the greatest

length of time was the most desirable.

The sum of values arrived at, as a resultant of all recorded study,

inventions and scientific deduction, up to the beginning of that time, as

Page 19

to protective treatment of wood, may be stated as:---

(1) That wood was susceptible of absorbing varied percentages

of liquids.

(2) That certain chemical solutions, when injected into the

cellular structure of wood and afterward dried, leave a residual

deposit of dry chemical therein, from which, with water, the

solution was originally formed.

(3) That such impregnation may be effected by pressure

mechanically applied and by incidental processes.

(4) That such deposit of chemical substance in the wood-cells

has in one case a preservative and in another a fire-resistant effect.

The saturation of wood to make it fire-resistant differed in many

respects from preservative treatment. Wood treated to make it

fire-resistant was subjected to many stringent requirements not

essential in the case of preservative. For instance, the saturation

must be complete to the heart. The color of the original wood must

not be impaired. The strength of fibre must be preserved. There

must be no lingering of flame on withdrawal of attacking flame. To

effect this, the strength of solution must be as high as possible. This,

of course, added to the cost and the density of solution required greater

pressure to infiltrate.

The effectiveness of ammonia salts to repel flame from a wood

surface depends upon the rapid volatilization of the ammoniacal gas.

The greater the applied heat, the more rapid the exhaustion of the

protective gas, and, when exhausted, no residual inert substance

Page 20

remains to bar the advance of flame or progress of disintegration.

The gaseous emission chemicals were the only known materials

used, up to five years ago, in any commercial fireproofing plant.

It became necessary to seek for practical materials, operating on

a reverse principle from the gaseous emission, and after years of

laborious effort sulphate of aluminum was discovered to be the

substance endowed with the property of fire-resistance inconceivably

beyond any previous conception. For instance, the best results from

the gaseous emission substances was an added life over untreated wood

of thirty-one minutes. The average of 2,800 pieces of 1-inch white

pine treated with sulphate of aluminum had an added life of seven

hours and thirty-eight minutes, or over fourteen times that of wood

treated with the gaseous emission chemicals.

This most satisfactory result came from the simple fact that

sulphate of aluminum under flame loses its water of crystallization,

its sulphuric acid of combination, and remains then residual pure

aluminum which has the admirable property of expansion in the

vacant cells of wood, to two and one-half or three times its original

volume of dry sulphate; and in doing so it interposes between flame

and wood fiber a compact mass of pure alumina, infusible by the flame

of any conflagration, and an admirable non-conductor of heat.

A casual remark was made by a prominent insurance man, to

the effect that the saturation of wood by sulphate of aluminum was

assuredly a great gain to it in fire-resistant quality, but that he was

quite as much, if not more, interested in the preservation of

Page 21

existent structures, from attack by fire, than he was in preparation

for protection of non-existent structures, or those only in

contemplation; and he counselled the serious study of this phase of

wood treatment.

Of the many enemies of wood exposed to sea water the

teredo worm is by far the worst. Any of the aforementioned

chemical solutions were useless against this animal because they

tended to wash out after a short while leaving any wooden structure

defenseless against attack by this worm.

At an early stage of growth the teredo is free swimming,

traveling about in the water and attacking any woodwork which may

have been left exposed, entering it by a hole not larger than a pin

head. After they have started their boring the teredoes grow not

only in length but also in diameter, and sometimes have been known

to have reached diameters as great as three-fourths of an inch. The teredo

is whitish in color, and has two small flexible tubes or siphons

continuously extending into the water from the small entrance hole in

the wood. It is very important that these vital organs be constantly

submerged in comparatively pure salt water, as it is through these

organs and from the water that the teredo gets his nourishment. Thus it

is that any substance which will permanently cut off the surface of the

wood from contact with pure salt water, will not only kill the teredoes

that are already in a pile but will prevent the entrance of other teredoes.

It is extremely difficult to inspect a pile and discover the presence

of the teredo until a vast amount of damage has been done, for the reason

Page 22

that although the interior may be perfectly honey combed, the exterior

presents an almost perfect appearance.

, #10 -Engineer Charles M. Ripley once took occasion to weigh a 3-foot

section of a 12-inch pile which had been withdrawn from a bridge in a bay

within a radius of 50 miles of New York city, and was astonished to find

that the weight of the section mentioned was but 11 per cent of its original

weight as yellow pine, which was calculated on a basis of 0.9 specific

gravity. This fact was more astonishing since there were no openings

upon the exterior of the pile save the tiny holes at which the teredo

originally entered.

It was once attempted in Holland to preserve the piling of dikes

by means of driving thousands of round-headed iron tacks into the pile.

Small boys were employed for this purpose and more or less success

attended it, but the expense is obviously prohibitory and on existing

structures the work can only extend from low water upward unless the

services of a diver were employed.

The copper sheathing method is a good protection. However,

copper is liable to corrode in salt water, not only at the joints, but

around the nail heads. The expense, both for material and for labor,

in applying copper is to be considered, as is also the fact that the

exact depth to which a pile is to be driven is not always known in

advance, and hence the copper sheathing is likely to be made to extend

either too close to the bottom of the pile, where it is useless in the

mud, or too high toward the top of the pile, where it is unnecessary

above the high water line.

Page 23

Engineers attempted to protect piles by means of tarred

burlap wound spirally around the pile. Materials floating down stream

tended to tear the burlap; also barnacles and oysters clinging to the

material after the tar was more or less covered with weeds and slime

tended to pull away the protection and leave the pile exposed near the


The lowering of the old mud line often occurs where the stream

is narrowed by the introduction of piling or other obstructions. The

tar burlap necessarily had difficulty penetrating the old mud line as

the pile was driven, and hence as the mud line later receded, the pile

was left exposed at the bottom, a point which couldn't be inspected

without a diver.

5LI1C 11 Concrete was used as a coating around piles, molds being placed

by divers and the concrete poured in; one difficulty incidental to this

method was that as the mixture was poured down through the water in

the mold it tended to weaken. Cases have been found where piles

protected by this method were really exposed at the bottom since nothing

but gravel descended through the water to that depth and the teredo

could enter the interstices between the grouting.

A later attempt was split vitrified pipes placed around the pile,

held in place by wires, and then filled with concrete.

Another method was ordinary sewer pipe strung over the top

of the pile and filled with sand. This method overcame the difficulty

mentioned in connection with a concrete covering or filling, as the

sand filling allowed the sewer pipe to descend as the mud line receded,

but in a new structure this method had to be installed before the deck

Page 24

was placed. In old structures caps of the piles must be removed

before the pipes could be placed. This obviously interfered with

the speed of construction of new work and also interfered with

traffic when applied to old structures. A serious objection is that

repairs to one section or one pile necessitated the removal of the cap

from that entire bent.

of time; and if one vulnerable spot shows, the teredo may enter in and work

destruction through the pile. All the methods mentioned-- -with the

exception of the sewer pipe---are liable to undermining. The coverings

are attached to the pile, and when the scour of the water removed the

wood or earth from the base, a line of attack was offered to the teredoes.

An improvement on the sewer pipe was the lockjoint pipe. This

consisted of sections of a concrete pipe, cast in halves so that could be

bolted round a pile when the latter is in position. The pipe was

larger than the pile, and the space between is filled up with fine sand.

Thus it was claimed that the pipe did not adhere to the pile but settled

gradually and followed the mud line, always keeping the pile protected

throughout the field of attacks of the marine wood borers. It may be

interesting in this connection to know that the teredo must have

continued access to the water in order to live. It is thus impossible

for the teredo to enter a pile above this protection and live so long as

this protection stands above the high water mark.15


1. Manual of Chemical Technology, Rudolph Von Wagner, D. Appleton
and Company, New York, 1897, page 944.

2. Scientific American Supplement,Vol. 68, page 78,

3. The American Architect, Vol. 81, page 12, "Protection and
preservation of wood".

4. Manual of Chemical Technology, Rudolph Von Wagner, D. Appleton
and Co. New York, 1897, page 946.

5. ibid, page 947.

6. A Treatise on the Resistance of Materials and Appendix on the
Preservation of Timber, De Volson Wood, John Wiley and Sons,
New York, 1883, page 285.

7. ibid

8. Manual of Chemical Technology, Rudolph Von Wagner, D. Appleton
and Company, New York, 1897, page 948.

9. ibid

10. A Treatise on the Resistance of Materials and Appendix on the
Preservation of Timber, De Volson Wood, John Wiley and Sons,
New York, 1883, page 284.

11. Scientific American Supplement, Vol. 66, page 78, Ag. 1, 08,
"Decay and how it may be checked", W.F. Sherfesee.

12. Scientific American, Vol. 95, page 79, Ag. 4, 06, "Sulpher
process for the preservation of wood."

13. Scientific American Supplement, Vol. 63, page 26216, My. 17, 07,
"Powell process of wood preservation with saccharine".

14. The American Architect, Vol. 81, page 12, "protection and
preservation of wood".

15. Scientific American Supplement, Vol. 67, page 12, "Destructive
marine wood borers." C.M. Ripley.


Manual of Chemical Technology, Rudolph Von Wagner, D. Appleton
and Company, New York, 1897.

A Treatise on the Resistance of Materials and Appendix on the
Preservation of Timber, De Volson Wood, John Wiley and Sons, New York,

Scientific American Suppliment

Vol. 59: 24281-2, Ja. 14, 05, "Creosote oil and timber

Vol. 66: 78-80, Ag. 1, 08,"Decay and how it may be checked",
W.F. Sherfesee.

Vol. 67: 12, Ja. 2, 09,"Destructive marine borers"' C.M. Ripley.

Vol. 67: 162, Mr. 13, 09, "Impregnation of timber".

Vol. 68: 147, S. 4, 09, "Methods of wood preservation".

Vol. 63: 26216-7, My. 17, 07, "Powell process of wood
preservation with saccharine".

Vol. 66: 222-4, 0. 3, 08, Primer of wood preservation",
W.F. Sherfesee.

Vol. 59: 24456-7, Ap. 1, 05, "Strength of timber treated with

Vol. 64: 311, N. 16, 07, "Timber and its protection from marine

Vol. 65: 356-8, Je. 6, 08, "Treatment of timber; open tank
method". C.G. Crawford.

Vol. 58: 24180-1, D. 3, 04, "Wood preservation".

Scientific American

Vol. 95: 79, Ag. 4, 06, "Sulpher process for the preservation
of wood".

Vol. 86: 91, Mr. 15, 02, Electrical process for preserving wood".

Vol. 83: 133, S. 1, 00, "Process for preserving wood".

American Architect

Vol. 60: 87, "Wood preserver".
Vol. 64: 78, "Timber preserving and fireproofing".

Vol. 81: 12, "Protection and preservation of wood".



Vol. 37: 182- 514, "Timber and some of its diseases".

Vol. 38: 108- 307, "Timber and some of its diseases".


Vol. 16: 326, "Preservation of timber".


1. "Piece of wood magnified 100 times", Nature, Vol. 37, page 185.

2. "Tank for treating fence posts", Scientific American Supplement,
Vol. 65, Je. 6, 08, page 356.

3. "Tank used for treating telephone poles", ibid

4. "Tank used for treating mine timbers", ibid, page 357.

5. "Diagram of small treatment plant", ibid.

6. "Powell process cylinder before closing", Scientific
American Supplement, Vol. 63. My. 11, 07, page 26216.

7. "The cylinder and trolley(Powell process)", ibid.

8. "Ash fellies", ibid.

9. "A section of balk riddled by teredoes", Scientific American
Supplement, Vol. 67, Ja. 2, 09, page 12.

10. "Another example of teredo destruction", ibid.

11. "Where the teredo does his work", ibid.

12. "Various methods of protecting wood piles", ibid.

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