PURSIURVATIVES, P IOI ITIS,
UNITED STATES DEPARTMENT OF AGRICULTURE
FOREST PRODUCTS LABORATORY
In Cooperation with the University of Wisconsin
Digitized by the Internet Archive
PI-3Zh-.VATVXS, IFRIOrJITIES, .:7P PROCZSC2-1
GERJB M. HUNT, Chief, Division of Wood Preservation
R. H. P.^CHIJL?, Che7.iist
J. OSCAR PL:' JR., Associate Technologist
Like m..ost other industries at this tiLue, the wo d-preserviung idustry
finds itself facing a serious emergency. During the year 1941 wood pr-servers
treated a considerably larger quantity of lum-ber and timber than in 19-. o
actual statistics are available on the am.aount of material treated in 1941 and
it will be some i.onths before such data can be published. ThE stte:.:ents
made by various individual plant operators, however, indicate strcn1l'J that
194-11 will show. a larger amount of timber treated than any other yczr since
1930. Whether this rate will be m.,aintained in 194'2 depends chiefly upon the
demands for new construction for military purposes or munitions production.
In tht; face of a great increase in demand for creosoted wood, there
has been a substantial decrease in the amount of creosote c-vailable ov-:ing
to a great decrease in the amount of creosote imported. This shortage is
felt Iost keenly by plants on or near the Atlantic, Gulf, and Pecific
Coasts, which have depended largely upon imported creosote but it is being
felt to so.ie extent throughout the country.
The i..;port statistics for the last quarter of 19l41 are not available
for publication but for the 9 months ending Septem.ber 30, 19%1, they ar&
reported by the Depart:.ment of Com.;.erce to have am.ounted to 12,971,656
gallons, which is probably very close to the total for the year. This is
about 1/3 of the amount imported in 1940 and about 3; m..illion gallonss less
than the average i.,portation for the years 1936 to 1i.z0 inclusive, "s is
indicated by the data in table 1.
What the creosote ii.ports in 19--2 will amount to, no one can safely
pr iict There appears to be plenty of creosote in the United M:. doi for
export des-itc its use there for fuel and, presum.,ably, we could lo I fo1.wa d
to a aa:ple suply if the oil could be transported ..ore freely. Sinc c i l
Presented at the 38th annual m..eeting of the AL.erican Wood-Prescrvw:rs'
Association, Minineapolis, :ii,:,esota, on January 27-2, 19-r2.
RI 2 84
imports and exports are under strict control, however, and are governed prima-
rily from the standpoint of military strategy and war-time economy, other
factors than the needs of the American wood-preserving industry must determine
the creosote import policy in 1942. Those in control realize that creosoted
wood is being used very largely on national defense construction, that it is
a necessity in the maintenance of our transportation, communications, and
power distribution systems, and that it is increasing in importance as a
substitute for steel in many types of construction. It seems probable that
enough foreign creosote could be allowed to enter the United States in 1942
to avoid plant shutdowns but it is certain that unlimited imports will not
be permitted and that surplus stocks of imported creosote will not be accumu-
There apparently was a large amount of creosote in storage in the
United States at the beginning of 1941. Treating plant operators could see
the prospective shortage coming and some of them, at least, kept their stor-
age tanks well filled. There was also a large quantity of creosote in the
tanks of the creosote producers and importers at the beginning of the year.
There is no way to obtain an accurate estimate of the amount of creosote
carried over from 1940 but it may have been 30 to 40 million gallons. This
was about enough to make up for the shortage in i:-,ports and was a very impor-
tant factor in enabling plant operators to increase the volume of timber
treated in 1941 despite the shortage of imports. This condition does not ex-
ist at the beginning of 1942, however, since the stored creosote has been
used up, and both the treating plants and the creosote suppliers have entered
the new year with very low stocks. One important supplier reports that,
although he will produce considerably more creosote in 19z.2 than in 1941,
he will have less oil to sell in 1942 because he enters the new year with
storage tanks practically dry.
A factor that has favored creosote plant operators in 1941 is the
increase in the amount of domestic creosote produced. This increase is diffi-
cult to estimate with any degree of accuracy, but it seems certain to fall
considerably short of compensating for the decrease in importations. Ax
increase in creosote production has been brought about by an increase in the
amount of tar available for distillation, an increase in the average yield
of creosote per gallon of tar distilled and, to a lesser extent, an increase
in tar distilling capacity.
n.- increase in the amount of tar produced in the country during
1941 has been a reflection of ncar-capacity operations of steel mills and
coke ovens. However, tar production has by no means run parallel with coke
production, The average yield of tar per ton of coal carbonized has fallen
Off as a result of the short coking periods which prevailed throughout the
,.',r in response to a heavy demand for coke; accordingly, tar production
41ill show a much smaller increase during 1941 thao, will coke production.
..e incrane in tar production has been offset to some extent by the lar-ie
*Pari-mts of *ar that were burned in open-hearth furnaces, especially during
ta'. firnt half of 1941. Local shortages of fuel oil or of tank cars, in-
crea .rL court of fuel oil, and difficulties of obtaining, fuel oil of suitable
quality, LuiJc all enc.coiraed the use of tar as fuel in open hearths. Thus
Table l.1.--T__,' .-f -:tl-t ,r ___ :-t. fl: v riu -* i; for the yer;rs
1936 to 1940 inclusivel
: A.iount of creosote i.pported
: 1936 : 1937 1938 1939 :
- - - - - - - - - - - ----: -
Gallons : Gallorns :
Belgiu .i ..........
United Ein do.....
1,026,429 : 2,
-- : 2,
4,644,584 : 5,
: ,11,753 12,
8 r C 3, 4 7
: 5,891,147 : 9,588,787
7 7,159,220 Z5 56 8, 565
6,261,601 :2, 11,49
1,089,3-0 : 6,139,92
:28,017,758 22,55, 836
S 18,372. : 8,14
Total :41,383,695 :58,189,527 :55,391,590 :51,876,602' :39,C- 9,788
Average annual i-iportation during the five years, 49,170,3O0 ,;al
-Data fro:.. published reports of U. S. Depart-,ent of Co..:..erco (Industrial
Reference Service, Part 1, Che.icls and Allid Products).
statistics for !9'-1, as copiXared with 1940, are expected to show a la%-,e in-
crease in coke production, a smaller increase in tar production, and a still
smaller increase in the amount of tar available for distillation.
Other conditions being the sa:e, the yield of creosote per gallon
of tar decreases with the coking period during which the tar is form.ed.
However, a co:.pensating factor has been an over-all increase in the distii-
lation residue of the creosote which has been brought about to so.es x t nt
by a refusal of some distillers to make a low-residue oil but, to a rer
extent, by cooperation between producers ann consumers. A considerable a,.ount
of low-residue oil has resulted fro,_ the production of roofing? pitch -nf o-
called electrode pitch which is a soft pitch that has been needed in rcl tive-
ly large amounts by the aluminum. industry. Ont. large steel co:Ipany has co_-
tinued to distill to a soft pitch to blend with fuel oil for open-huarth fu.l
and, in so doing, has produced a low-residue creosote. However, th ,eeral
trend has been in the direction of higher residues.
The outlook for 194-2, of course, is uncertain, but indications
point to a further increase in domestic production of creosote over tiat of
1941. The supply of tar available for distillation see..s to b. the liiting
factor; tar distilling capacity has not yet been fully utilized. The tive
demand by defense industries for coal-tar products other thrn creosote, es-
pecially naphthalene and the tar acids required for the _anufacture of
plastics, should influence the official policy in a maniecr fav oral. to the
wood-preserving industry. The O.P.M. apparently has already been resosibl
for an increase in the amount of tar available for distillation by indu ing
certain steel .ills to substitute fuel oil for tar. It does not sc likely,
however, that domestic production alone, even when accelerated to the _-tont
that -ay reasonably be expected, can supply all the creosote' needed 7t ,he
1941 rate of consu..ption. On the other hand, a decrease in dem.;ana for cre -
soted ti:ber would ease the situation appreciably.
Supply of Salt Preservatives
The su-ply of salt preservative s in 1941 apparently was suffcient
for we have received no reports that th- operation of any treating plelt
has been hindered by a shortage of salt pr servatives, although the .ount lof
timber treated vith preservative salts in 1941 was prob'-bly so.ewhat r.r
than in 1940, This favorable situ tion will not necessarily co ntinuc in
1942, however, for it can very easily be changvd by ._ilitary r require. nts
and the decisions of the controlling ag'. cies.
At th,. ti;.e this is written, th(rc sec ..s no i:...edi' t.c d -,.:er 1)f
a ser os sotge of zinc chloride. T sof zi'ac ore0. hydri-
chloric acid a, ie)car to be adequate( and there is no i. mediate rosct ,
this situation will change but we have a..ple evitienc e. th :7 t t. c ..
place very suddenly. The a.,ount of zinc chloride usLd for wood presr-i.n
in 1940, irnclriirng that used straight as well as that, in chro..r-,ted zinc
chloride, totalled about 4-1/2 million pounds (14). The 1941 total is, of
course, not yet available, but it was undoubtedly higher.
Zinc is also a necessary ingredient in zinc-meta-arsenite, of
which some 200,000 Ibs. were used for wood preservation in 1940. In pre-
parin.: this preservative, the zinc is used in the form of zinc oxide and the
arsenic in the form of arsenious oxide (AS207). The supply of either one
is not unlimited but has apparently been equal to the need thus far.
Chromium salts are, of course, important ingredients in several of
the salt preservatives in extensive use. Sodium dichromate makes up about
18 percent of the weight of chromated zinc chloride and about 50 percent of
Celcure, while Tanalith (Wolman salt) averages about 37-1/2 percent sodium
chromate. TU amounts of these preservatives reported used in 1940 (14) and
the calculated amounts of chromium salts they contained are as follows:
Preservative : Amount used in : Chromium salts
S P.unhs Pounds
Celcure..................... 242,739 : 121,370 (sodium di-
Chromated zinc chloride..... : 3,960,896 : 712,961 (sodium di-
Wolman salts (Tanalith).....: 1,062,048 : 398,268 (Sodium
Total chromium salts 1,232,599
Th,: 1-1/4 million pounds of chromium salts used for wood preser-
vation in 1940 were no doubt considerably exceeded in 1941.
With chromium salts, the situation is quite different than with
zinc chloride for dependence must be placed almost entirely upon imported
chromium ores. As a result, the amounts of chromium ore that refineries
may consume aid the uses and allocations of c iromium and chromium chemicals
are under very strict control b, the Governmcnt. ,,turally, the most urgent
national defense uses receive hihLest priority ratings and nondefense uses
arc largely eliminated. The increase in chromium salts used by wood-prcserving
plaints in 1.41- over 1940, in thc face of these restrictions, is possibly at-
tributab le to the fact that salt treatments in 1941 were considered ir.ly
r.s underlined in pi.rcntheses refer to list of references at the end of
for high-priority national defense structures. A prediction by th. writers
of what to expect in 1942 with regard to the chromate supply would :. ir
gue s swork.
In addition to thL chemicals nomed above, sodium fluoride, sodium
arsenate, and dinitrophenol are necessary ingredients in Wolm;iin salts.
Copper sulphate constitutes 50 percent of Celcure preservative. Of t:' se
chemicals, dinitrophenol and sodium fluoride are under close control :ut the
supplies of all have been low for some time and their availability for wood
preservation in 1942 will be so largely determined by needs for other uses
that it cannot be predicted by the writers.
Other Pr. s-rvati- .'e sh:uli I : C, id,.
Although an acute preservative shortage does not appear certain,
treating plant operators and users of treated wood will be unw ise if they
ignore the possibility that economic and military developments may chfn
creosote was limited, there was plenty of zinc chloride avrilable and the
amount consumed per year rose from 26 million pounds in 1917 to more thun
51 million pounds in 1921. That is not likely to happen this time, however,
because there are other substitutes for creosote that -re much better than
zinc chloride for outdoor use. During the 1918 to 1921 emergency, also, thu
use of creosote-petroleum solution began in earnest but this practice has
proved so effective that it has increased greatly since thct time.
In considering what can be done in the event of inadequate supplies
of creosote and of the customary salt prcservatives, it is well to sec Khat
has already been done in some cases.
One large consumer of creosote-petroleum solution, who custo:.arily
has used not less than 50 percent of creosote in the mixture has had to r -
duce the percentage of creosote by half. In view of th uncertainty that
this preservative will be sufficiently cffeotive in the usual absorption,
he has increased the absor-otion from about 8 to 10 pounds per cu. ft. The
net result of the change is that the ties receive only 2.5 lbs. of creosote
per cu, ft., which is a net saving of at least 1.5 lb. of creosote per cu.
ft. N-i general, shortage of petroleum for wood preservation is anticipated
but there may be temporary or local shortages due to trans-ortation diffi-
Other consumers, who have for many years insisted on creosotes
with-not over 20 percent (or Q5 percent) distillation residue about 3S5c.
have been unable to secure adequate quantities of such oil and, for th_ time
being, have raised the acceptable limit to 70 percent or even hither. Steps
are now being taken to amend the Federal specifications for creosote l:nd lor
creosote-petroleum solutions, for the duration of the war, so .s to permit
residues ap to 35 percent. In general, a 5 percent increase in residue
above 355Df, shornld" increase the yield of creosote from tar by about the
sBne percent ..--., which is important in a time of short.ge.
-Th' consumers referred to felt that they had good reasons for their
former preference for a high percentage of creosote in their creosote-
petroleum solutions and for relatively low residue creosote. The c?.-i. ;os
.,ade do not constitute an abandonment of their former preferences but merely
a realistic attitude and a logical conformance to the requirements of an cmer-
gency. Their emergency preservatives arc still good preservatives, even
though they may be less desirable in some respects than their preferred prc-
servatives, to which they will probably return when that becomes r.'tcticaclc.
actingg practices, wood species, and the availability of suitable
materials vary considerably throughout the United States and the sup ly of
usable preservatives may also vary at any place from month to month. For
these reasons, it is not to be expected that any one material can serve as
the universal substitute when supplies of creosote or preferred salt pre-
servatives fail. It is desirable, therefore, for both plant operators and
users of creosoted wood to study the various possible substitutes and thus to
have several to choose from, according to local availability of materials
and the needs of the job to be done. The following discussion of preservatives
and processes is presented in the hope that it will be useful in that connec-
Toxic 'Oils Other Than Creosote
Certain toxic oils other than coal-tar creosote are available to
the wood-preserving industry. Some have been tested in service so that
their degree of effectiveness is reasonably well established; others are
still unproven and their use is attended with greater uncertainty as to re-
sults. In either event, they should receive careful consideration.
Chlorinated phenols.--Solutions of polychlorinated phenols in
petroleum solvents have been attracting attention for some years as pros-
pective competitors of both creosote and salt treatments. The most proii-
nent of the group in the last few years has been pentachlorphenol but tetra-
rhlorphenol and 2-chlororthophenylphenol have also received attention. All
three have high toxicities to wood destro:'i'-: fungi. Batcm.ian and Baechler
( ) report killing points of 0.0C2 against the fungus ":,-ison 517" for
penta- and tctrachlorphenol. Carswell and Hatfield (6) reported a killing
point of 0.006 for pcntachlorphenol and Hatfield (10) reported 0.009 to
0.01 for 2-chlororthophenylphenol. Trh.se toxicity values are not strictly
comparable because of some differences in methods. .Th'y also cannot be
compared directly with creosote toxicities for the latter vary widely,
according; to the character of the creosote. The toxicity of penta- -nd
tetrachlorphenol, however, appears to be from 10 to 100 times that of coal-
tar creosote, depending upon thc creosote and the to:.icity values used for
comparison. '.'.n when diluted to 5 percent concentrations, the toxicities
of the 3 chlorinated phenols a;pear to be equal to or greater than the
tox-icictire of th.e coal-tar creosotes in common use. From th standpoint of
toxicity then, S percent solutions of these chemicals appear suitablefor
wood *or iarv(tion wini used in sufficient absorptioni.
Toxicity alone is, of course, no assurance of prm.servative ff-
tiveness since permanence, as measured by che..iiccl stability, volatility,
and leachability in water, is equally important. In thcso respects, )cnta-
chlor-ohenol is reported (7)to be highly satisfactory and the other t',,'o, from
such other information as is thus far available, are also satisfactory.
Laboratory tests, no matter how extensive, are not a final measure
of the value of a preservative -nd wood preservers naturally want to knor th'
results of service tests and actual use experience. Although solutions of
these 3 chlorinated phenols have been used alone or in mixtures (20) :'for
some years as preservativess for w".indow sash and other millwork, very little
information of value to the pressure treating industry is available fro;:
this experience. Th. absorption and penetrations obtained in the 50-.inute
immersion treatment, which is the minimum standard treatment of the iTati onal
Door i-anufacturcrs Association '(20), are rather low, the service conditions
are usually not comparable to those for structural timbers, and service
records on treated millwork are almost entirely lacking. YTevertheless, the
results obtained appear to have been generally favorable.
The manufacturers of the chlorinated phenols hvc numerous service
tests under way which include treated saplings, 2 by 4-inch stakes, fence
posts, and other forms of experimental material. Most of these are CgroDuc
tests in which exposure is to decay and termites but some arc salt x.at2r
tests. Data from all these experiments are said to indicate a satisfactory
degree of protection when suitable absorptions and penetrations were used
but the data have not yet been published. A considerable nuantity of
lumber, land piles, poles, and other structural material has also been pres-
sure treated with pentachlorphenol solutions, some for railroad use. !-ost
of it has been installed too recently to furnish service data of value and
no results have been made public on any of it.
As carly as 1931, 2 by 4-inch test specimens were treated by the
Forest Products Laboratory with alcohol solutions and with petroleum solu-
tions of tetrachlorphenol and installed in the Barro Colorado Island tests
(1__2). Still other tests with pentachlorphenol solutions in 2 by 4-inch test
specimens have been started by the Laboratory in cooperation with a preserva-
tive co00pany but too recently to -rovide useful information. In 1934 the
Forest Products Laboratory started field tests on fence costs pressure, treated
with solutions of tetrachlorphenol in waste crank case oil and, since th t
date, has started other field tests in which solutions of tctrachlorpiAiol
or pentaclilorphenol have been used for fence post treatment. Thr; rcs olts
av.'.il'ble to d'te from these various tests are given in table 2, together
with some results with creosote and creosote-petroleum solutions in the same
...ik:ation of table 2 shows tha t in most of the uxptrimcnts,
Pentachlorphenol and tetrachlorphenol solutions are giving good results.
Poorest results have been obtained when using alcohol as a solvnt. ?ance
posts aypear to be givih better results than 2 by 4-inch t st secimens.
ThCis is true with creosote anlid creosotc-petroleum, solutions "s -',ell as. '-ith
the chlorinated pheiiol solutions. It is probably due in p-'rt to tn rc ter
area exposed per unit volume in the smaller spccimtns, and partly to the
severity of the exposlure ooniitions.
ITh.'se experiments do not settle the question of the relative
effectiveness of creosote and solutions of chlorinated :Th-nols nor do they
determine the optimum concentration of solution or absorptions to be used
with such solutions. Tnacy indicate, however, that petroleum solutions of
pentachlorphenol and of tetrachlorphenol, when of sufficient concentration
an.1 retention, can give a high degree of protection against decay anc ter.ites
and arc promising materials to use when creosote is hard to get or is too ex-
pensive. It is highly desirable that all other obtainable data frou experi-
..ents and from use experience with these preservatives be made available as
soon a.s p ossibloe
Pentachlorphenol and tetrachlorphenol are much m.ore versatile pre-
servatives than creosote for they are sold as technically pure solids or in
concentrated solutions and can be carried in a, variety of solvents. Where
stronger solutions than 5 percent are required they can easily be made. here
practically colorless treatment or nonbleeding treatment is desired, it can
be obtained .- choosing suitable solvents. In using creosote-petroleun
solutions with a low concentration of creosote, pcntachlorphenol may be r"dded
to increase the toxicity.
On the other hand, it is still wise to be cautious and conservative.
-..:re is a tendency for some promoters of pcntachlorphcnol preservatives to
make extravagant claims for their products. Rem'rk.ble penetrating proper-
ties.are -iost frequently claimed and the easily convinced are misled into
believing that superficial treatments with pentachlorphenol solutions are
equal to pressure treatments with creosote or accepted salt solutions. This
idea is not new, of course, for similar claims arc made for ..anv proprietary
preservatives, including several of the creosote or carbol.i.. *-.. type. In
considering such claims, it should be re..e,.bered that pen ;" .henol and
retrachlorphonol by themselves do not penetrate wood and 1'. c penetra-
tions obtained with their solutions depend upon the solvents chosen and the
treating conditions used. Petroleum solvents of very low viscosity do
penetrate better than creosote, which has higher viscosity. Substantial
absorptions and deep penetrations can often be obtained in easily treatable
wood by .icerelyr soaking it for a day or .-iore in low viscosity solutions of
pentachlorphonol -t at.-iospheric temperatures. Rather surprising results
can 'iso be obtrincd with creosote under the sae..o conditions. '..re is no
known practical solvent, however, thtt penetrates deeply rnd quickly into
wood that is resistant to penetration. The cheap byproduct petroleum. oils
of the fuel oil type ordinarily have viscosities as high as creosote, or
higher, and cannot be expected to excel creosote in penetratin._ properties.
The cost of pentachlorphenol will undoubtedly have ..,uch to do with
its ability to compete with creosote in the 'future but, unecr present ab-
nor.,al conditions, availability .,: yr often be ..more important than cost. PCenta-
chlorphenol solutions appear to be as freely available now as creosote and at
competitive costs but the situation can be changed at any time by priority
orders. For this reason, it cannot safely be predicted that r.rntachlor-
pheol solutions will twke up the slack if the creosote supply becoiimes in-
adequate. After the war the supply of both creosote and pentachlorphenol
eho-ld. b adIqu;te and cost will be a much .iore important factor. Creosote
will still li.ve the advant"-e of a century of successful use experience, but
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if experience with pcntechlorphenol solutions continues to be favorable and
their cost per unit of timber treated is lower than that of creosotE, their
use is likely to grow at the expense of creosote.
'' ter-a.s jtar.--Iost of the vater-gas tar now being produced is
used in road tars. The exact amount used in wood preservation, including ths.t
which is distilled to produce a creosote and that which is blended with cl-
tar creosote, is difficult to ascertain. Water-gas tar varies greatly il
viscosity according to the oil from which it is made, as well -s th. condi-
tions of :.manufacture. :.uch of it is too viscous to be suitable for .wood
preservation but satisfactory absorptions and penetrations ;:ay be obtained
with the less viscous tars. Service tests (2, 24) show that oater-gas tar
is a vcry good preservative when properly applied and is well worth conoider-
ing as a substitute for coal-tar creosote for land use.
Loi-tc.-'-er ,-turc t-r.- ani creovotes.--Low-te.:perature coal-tar
creosotes differ in chemical composition froL high-te;:perature coal-tar creo-
sotes as shown by pronounced differences in a number of properties, such as
specific gravity of fractions, sulfon-tion residue, tar-acid content, and
naphthalene content. Soie of the. have given very good results in service
tests (2) and a paper by Dr. Reid (22) reports interesting and favorable
laboratory data about another. The total a:.ount of these oils availabl. for
wood reservation is not larje end apparently it is being used .ainly. inl
mixture with high-temperature coal-tar creosote.
The tar produced by thc Curran-Knowles process is so,.mtim.es re-
ferred to as a low-te.:perature tar, but in most of its characteristics it
lies between a high-temperature and a true low-temperature coal t:,.r. T>e
few service tests that have been started on the tar alone have not yet
reached a stage where conclusions .iay be drawn. At present all of it is
said to be sold for wood-preservation purposes !nd is used undistillcd and
mixed with coal-tar creosote. It apparently finds fa-or for this purpose
m=-iso of its low' viscosity, distillation residue, and benzol-insoluble
Th-- low-te:.rperature coal tars and Curran-Xno'wlcs tars produced
in the United States result for the most part from the manufacture of s.oke-
less domestic fuel. Certain indications point to an increased use of these
processes in the future, but because of priorities on building material
any great expansion in any of the is not to be e-pected for so..e tie. -:he
total production of thise ;.ateri4so probably com.prises less than I percent of
the coal-tar creosote used annually.
Lignite coal-tar creosote has been used by one railroad company for
some years, in Amixture with coal-tar creosote and petroleum oil. The lim-ited
service data thus far available (24) fail to show that lignite-tar c. eoote
is equal to coal-tar creosote, but in certain regions and under certain -on-
ditions its use m.ay well be an eco:noq.
The ?Portland G-as and Coke Com..any, in carboniizing- petroluu. oils
for the Maxufa.c.ture of ounicipal gas, produces an oil tar fro-.. which
creosote may be distilled. Some tests on this creosote (23) by the block
method indicate that it has considerable promise as a wood preservative.
Aromatic petroleum oils.--The importance that petroleum oils used
as diluents of creosote have assumed in the wood-preserving industry is well
.recognized and the possibility of extending our supplies of creosote by re-
ducing the creosote percentage in these mixtures has been mentioned. In ad-
dition to furnishing the inert oils that are now being used as diluents or
solvents, thle petroleum refining industry might be a source of toxic oils.
This field, which has been sporadically explored in the past, is now of re-
newed interest because of changes in conditions. As a general rule, straight
distillate oils from petroleum are too insoluble to kill wood-destroying fumni
growing either on agar or wood. They usually exert some retarding effect and
within a _iven boiling range the tendency to be toxic increases wita t'e
aromaticity of the oil. By the use of certain preferential solvents, it is
possible to extract from petroleum oils, constituents that will kill wood-
In cracking heavy petroleum oils to produce gasoline, the un-
converted residual oils tend to increase in aromaticity. In applyii the
different basic cracking processes and their variations to different crudes,
a large number of different oils of varied properties are produced by the
petroleum industry. Certain refining processes other than cracking also
tend to increase the aromaticity of oils. The yields of some of these oils
are small on a percentage basis but, because of the tremendous volume of oil
processed, the volumes of the byproducts are large by standards of the wood-
Determinations of toxicity have been made on a number of sales of
aromatic petroleum oils. As a general rule, they are not quite soluble enough
to kill the organism growing on agar, but their inherent toxicity is shown
by the fact that very small amounts permit only a very feeble -rowth. It is
possible that these oils would show fairly good preservative properties in
service and it uii-ht be possible to fortify them with relatively small
amounts of toxic chemicals or creosote. Some preliminary tests have indicated
that mixtures of creosote and aromatic petroleum oils may be more toxic than
equivalent inixtures of creosote and petroleum oils now being used in the wood-
preserving industry. It is hoped that these studies may be continued.
One patented process (2l) is said to produce an oil from petroleum
residues that is practically identical with coal-tar creosote so far as all
ordinary tests show. If this can be substantiated, it will be of great
interest, but thus far, little if any progress has been made towards commer-
cial production of the oil.
I-' *r orn :, taz.--Althou h ~1rood-tar creosotes have been av.il-
able in smali quantities for many years, they have never been used extensively
In pressure treatments. This hds been due in part to the relatively lir.1ited
Tquantities jjroduced and, to some degree perhaps, to l;Ic': of sufficient stan-
dr rdiz-;.tion, Frr the most part, these products appear to have been sol0. for
nr'npres-,ure use although there have been substantial exceptions.
No very positive statements can be zarde about the effectiveness of
wood-tar creosotes because of the differences in character of the prod-ucts
obtained frou different sources. The tcst data available indicate a consider-
able degree of effectiveness but do not show that the wood-tar creosotes can
be safely assumed to be equal to coal-tar creosotes. Red oak tis ''ith an
absorption of about 10 lbs. of wood-tar creosote per cu. ft., in test for 1.
years at Madison, Wisconsin, (2) will probably have an average life of a-bout
20 years or .iore. Another group of hardwood ties in the s;...e test th:t rc
.. cstly red oa
about 27 years or more.
In the ForLst Service fence post study in Mississippi (24) southern
pine fence posts pressure treated with 6.6 Ibs. of a wood-tar creosote per
cu. ft. were showing -.,ore deterioration at the end of 3 years than si..ilar
treat.-ents with coal-tar creosote or a 50-50 mixturee of coal-tar creosote
and waste crank-case oil. In the Barro Colorado Island tests also (15) the
spcciuens treated with wood-tar creosote are not standing up quite so weil
as those treated with coal-tar creosote.
While the evidence fails to indicate that wood-tar creosotes -'re
equal to coal-tar creosotes in ability to prevent decay and ter;:ite attack,
the wood-tar creosotes do have considerable protective value. They have
been used occasionally in the past in mixture with coal-tar creosote, as
an acco::..odation to the wood-tar producer. Opportunities .-.ay now occur
when this would be of advantage to both the producer and the user of the
wood-tar creosote, and thus serve to extend the supply of coal-tar creosote.
When such mixtures are conte.2plated, it will be advisable to consider the
quality of the wood-tar creosote very carefully and, if possible, have it
ieet a definite specification. High acidity and high voltility in the
wood-tar product should be avoided. Tests should also be :.-ade to assure
that the oils used will ilix satisfactorily without producing a slud.-: during
the .iixing operation or subsequent heating.
Thr.I.t-nh.e3.--Copper naphthenate and, probably, soue of the other
metallic naphthenates have considerable value as wood preservatives. -.. ir
use, up to the present tir.me has been confined almost exclusively to surface
applications which necessarily has limited their effectiv-ness and, until
very recently, they were sold only in proprietary preservatives. One such
preservative has been in use for .iany years in Europe, particularly in
Denmark and in England, but the sale of naphthenate preservatives in the
United States appears to have only begun during the last or 5 years. The
growing interest in the naphthenates as prC-servatives appearss to arise frog.
the increasing quantities of naphthenic acids being pro 'uced as by products
of the petroleum industry and the urge to find ...rkets for the:-.
The effectiveness of the nmphthienat-s C wood prescrvawiv s has
not received adequate study and no data are available a.s to th. absor tions
that should be injected for best results. It is possible that petroleu.n
solutions of copper naphthenate could be u.:ade to protect wood -,s wE;ll 's
creosote does but it rei.ains to be seen what solution conce(ntrations and
absorotions would be necessary and whether they would b1. ccono;.;ically
feasible. i;: frag.-..ntary information available fro:.- various minor studies
of coo-ner nai-hthenEte give favorable indications with regard to toxicity,
permanence, and field tests. rush treat.,.ents with a naphthenrte preserva-
tive a-rc said to have given only mediocre protection but apparently satis-
fact ory protection from substantial absorptions injected by pressure. Field
tests have been started recently by the Forest Products Laboratory, in
cooperation with a producer of naphthenates, in which surface and i.-pren-na-
tion treatments in a variety of absorptions arc being compared but thl-sc
tests will yield no results in time for the present emergency.
It see.s doubtful that copper naphthcnate will be sufficiently
plentiful or cheap in the near future to be of much use os a substitute for
creosote in pressure treatments. At prices co.,parative with current creosote
prices, hoevcver, copper naphthcnate solutions would warrant serious conrsidcra-
tion. They a; pear sufficiLntly promising to justify extensive experimental
use even now, despite their present cost.
Preservative Salt -- Oil Treatments
C'rd t-'. t.,cnt.--The Card treatment with mixture of creosote and
zinc chloride solution,' which was used extensively for tic treat.:.ent prior
to 1934, was originally developed as a means of economizing on cost by re-
ducin, the amount of creosote used per tie. It does not offer much of value
in the present situation, however, because equal or greater saving of creo-
sote cane'be accomplished by using creosote-petroleum., solutions, which are
more desirable and more effective than the Card mixture.
Zii.L ,hlorid --petr.r-.leu. t r, t:..,-- its.--Several types of zinc chloride-
petroleuw.i tie!at:..nts have been described by E. R. Boller (5). Since these
treat-.ents use no creosote, they have a distinct advantage over Card ...ixtures
fro.., the standpoint of creosote economy. Service records are not sufficiently
comprehensive or coi.plete to per:.lit an exact co:.parison between these two
treatments but it see..s suite possible that the petroleum. combination wouldd
at least equal the Card .-ixture in effectiveness and, bNcause of the larger
amount of petrolu:u.i oil injected per cu. ft., it mi-ight exceed the Card treat-
.eCnt. The effectiveness of the zinc chloride-petroleum treatment can
undoubtedly be varied considerably, according, to the absorption of zinc
chloride .nd petroleum used.
A disadvantage of the zinc chloride-petroleum treat:.,ent is that it
is a two-m..ove..,ent process and, therefore, more complicated and expensive
than a one-,ove.ent process. Another disadvantage is the uncertainty as to
the zinc chloride supply but this is true of practically all preservativ-s.
Combination salt and oil treat..ments are not limited to zinc
chloride but are possible with all accepted salt preservatives. Zinc
chloride has the advantage over the other salt preservatives for this
pVirpose, h)wever, in that its solutions can be heated to over 200'F.
without causing undesirable che:.mical reactions that reduce the concentration
of pro erwv.tivw in the solution. This permits a high-tempcrature Ruepin.
treat:.ent with the zinc chloride solution, followed by a vacuum th:'t v-'Dorates
soLe of the surplus water, end then the iu.ediate application of the -il tro-t-
uent. With preservative salts that cannot be heated to such high t.: )r.turts,
less water is rc..ioved during the vacuum period and the wet wood is lcsr sit-
able for the oil treatment. Air seasoning bet,.een the salt treat... .nt ..the
oil treat:.ient will, of course, remove the excess water and put the wood in
excellent condition to receive a good oil treatment. This ..ithod is r' cti '-
ble with all the salt preservatives but the extra handling, for seasonin, -1nd
retreat:.ent is expensive and the ti:e required for the scasoninr prolol:s t: e
In short, petroleu.-salt treatment can be applied in various u ass,
gives.lonjer life than straight salt treatment, and avoids the use of creo-
sote but has th disadvantage of being a two-Lovecent treat:.Icnt.
Other Preservative Salts
Wi pr. servative salts thus far mentionedd nai.;ely, Celcure,
chrom.ated zinc chloride, Tanalith, zinc chloride, and Zi-, re not the only
water-borne, salt-type, preservatives that can be used. Various others ar' e
known that have i.ore or less value .ven though not so extensively used.
Tnitir cost, availability, priority liz1itc'tions, and other considerations
greatly linit the ability of these .ateriols to relieve the short .e of0
other preservatives, nevertheless they .-ay in individual cases be very
practical and economical to use and they should, not be ov-rlooked. Aong
thea are the following:
Aczol is a proprietary preservative solution cont'aining co r
and zinc salts and a..onia. In one test (13) Aczol in heavy absortions h',s
given excellent results but in another t st (2) it has not done so icll. It
seems unlikely that Aczol can be aade available in sufficient ouantity to
contribute .much to the relief of thi shortage of creosote and other pre-
servatives or theft it will be economical to use in th. high absorptions ,hr.t
appear to be desirable for a high degree of protection. Teverthcliss, Aczol
undoubtedly has preservative value and should receive consideration w:en it
is available in an ,.tergency.
Borax has been shown (4) to have greater toxicity to fungi than
zinc chloride and in a service test on 200 rcd oak ties (2) with absorptions
of 0.24 and 0.59 lbs. of borax per cu. ft., only about 4 percent have boen
removed for decay in 13 years. A group of 31 southern yellow pine fence
posts pressure treated with an. average 1.05 Ibs. of borax per cu. ft. ..ows
about 55 percent removals after 15 years service in Wisconsin. The Bn'rro
Colorado Island tests (13) indicate that borax treated wood in contact with
the ground -oos not have high resistance to ter.-ites but it cannot co deter-
ained from these tests whether the lack of resistance was due to leaching
or to low inherent toxicity to termites. Until that question is settled,
it would not be wise to depend upon borax for protection Lgainst ter..itCes,
even where there is no opportunity for leaching.
Borax is rather strongly alkaline in reaction and iay possibly
have some effect on the strength of the wood. The service tests thus far
fail to indicate any adverse effect on strength but they are no proof that
there is no such effect. So far as fence posts and similar products arc
concerned there seeuLs little to fear, but for timbers that gust carry heavy
loads some caution should be exercised.
Batean and Baechler (4) suggested that a :mixture of borax and
boric acid, being neutral in reaction, would be less likely to dainage the wood
(and paint) and would still be nearly as toxic to fungi as the straight borax
solution. Only one service test of such a Lixturc appears to have been
started (24). One hundred southern yellow pine fence posts pressure treated
with an average absorption of 0.9 lbs. of 50-50 borax-boric acid per cu. ft.
and placed in test on the Harrison Experimental Forest in Mississippi showed
no re:.ovals at the end of 4 years but 4 percent were showing evidence of
term..ite at tack.
In norv.al tines, bora-x is cheap and plentiful and the borax-boric
acid .:tare should be competitive in cost with other salt preservatives.
Under present conditions the dei.and for borax for other uses is heavy and
its availability for wood preservation is questionable. This situation Liay
change, however, for there is plenty of borax in the ground and increasing
the refining capacity could provide all the borax and. boric acid needed for
all uses. "!.?.ther th. t will be accomplished in the near future we are unable
Crc. :nitc is a proprietary copper-arsenic-ar.L.onia wood preserva-
tive (8) that has found sonc coia..ercial use on the Pacific Coast. Its
continued availability obviously will depend upon the availability of the
chemicals of which it is coi.iposed. The preservative has not been fully
evaluated or generally accepted nor is it yet certain that the optiuum ab-
sorptions have been arrived at. Nevertheless it appears to be doinr, very
well in unreported service tests and there can be no doubt that Cheuonite
preservative, when properly applied, can give a considerable degree of pro-
tection against decay and termites to wood in contact 1ith the ground. It
has not yet reached the' stage of development that would justify its general
acceptance cs a so-called "standard" preservative because it has not had
sufficiently etensive use over a long period of tii.;e. T'. results that
have been obtained to date, however, are very pro.:iising and justify favorable
consideration. It certainly should not be ignored for land use where it
is economically available and where it may often be a practical alternate to
turn to in emergency. Its suitability for marine use is open to question
and has not been sufficiently doiionstrated to justify our reco:.-i.,cndinr;, it
for the protection of piles in salt water.
Mineralized-cell preservative --This is a proprietary preservative
aaid to contain zr.caic- trioxide, zinc sulphate, and copper sulphate, all
of which are known to have preservative value. It stands to reason, there-
fore, that wood properly impregnated with a sufficient absorption of this
.Aixture will have its decay and ter;Aite resistance in-reased. Since the
preservative has found so.i, use for the treatment of piles in Pacific
Northwest for a number of years, it should be possible to obtain service
records that indicate the anitude of its effectiveness but none arc knowr
to have been published. It is not reasonable to suppose that a prescrvativc
of this character would give Luch protection to piles in salt afterr an thec
published (18) and unpublished information available recomLcncds stronrJly
against its use for that purpose. It may, however, compare ,ell with vario.u
other salt preservatives for land use and iay properly receive co inor(tio:
for such use when available in an emergency.
Miscellaneous salts.--There are, of course, other salts, which
either should have or are known to have more or less preservative value,
that have not been used to any significant extent for co.- crcial pressure
treat..ients, if at all. Such salts, however, are unlikely to be fr1g 'v- il-
able now. About all that need be said about theo now is that they could
probably be used to advantage if they were available at reasonable co.t.
A.-..:.- these are mercuric chloride, which is a powerful preservative but
expensive, corrosive and poisonous; Boliden salt (9); grecnsalt (Ascu)
(17,19); sodiu:., fluoride; copper sulphate; arsonatos anid other salts "
nickel; and a variety of others that have been included in various fie-ld
experiments but not co:.mercialized as wood preservatives.
To the operators of coi..ercial pressure treating plants, there.
would seldom, if ever, be any advantage in turning; to a nonpressure treat.uent.
For the user of pressure treated wood, however, certain nonpressurc trat-
uents ray be useful in an Emi.ergency when the customLary pres-ure treated
materiel is unavailable. Similarly, users of butt-creosoted polos, in lacing
a creosote shortage ,.,ay have to turn to other methods s as well as gruservativcs.
S ta:di:-i ,I pC tr-.: t ..-.--Standing poles tha t have begun to de-
cay at the ground line can have their service life -aterially prolo:,Ce byi
ground line treatment if the upper parts arc in good condition and the decay
at the rou,.. line has not progressed too far. Several types of such .ra t-
aents have developed during the last 10 or 16 years. Their rlativo effectvc-
nose and ccono:a-y has not been worked out but enough information has boc n
obtained to indicate that a nuwiber of the:.: have ierit under nor.-,ial econo...ic
conditions and that they can extend the life of poles several years. I the
present emergency they ...ay prove very useful to public utilities in t. event
of a shortage of their preferred creosoted poles and ,,with the necessity of
making their standing poles last longer.
These various ground line treat.-.ents have been described in publi-
cations or are being actively promoted by th ir proprietors mnd it secr :-
necessary to describe thea individually here. Several of these treati.g
mLethodcs use coal-tar creosote, including the charring and sprayin e :..L thod (_l',
the "saI-oollar" .ethod developed by the Hydro-Electric Power Co;:.isvion of
%ntario (_15), the "iLpr ,o7.-:ted sawdust collar'1 method (16), pouring creosote
in. ,he earth arou-and the poles, and no doubt others. 'e.c of cours.., use
less creosote per pole than is required to treat a new pole and in that way
economize on creosote. Still greater creosote econo-my is obtainable, however,
by using pole base treatments that contain less creosote, such as the Osmose
and Pfister treatments, or the Anaconda arsenic paste method, which uses no
The ......se r-nth:d.--The Os..- ose method is a nonpressure method of
treating luber, poles, mine timbers, posts, and similar materials in the
green condition and without the use of creosote. Its economy and effective-
mess in co-poarison with "standard" preservatives and treatments re...ain to be
worked out. No doubt they vary widely under different circumstances, The
fluoride-chro.ate- arsenic-phenol preservative that is applied to the surface
of the wood in paste form does penetrate appreciably under favorable circum-
stance-, however, particularly in sapwood. Such treatment should have effec-
tiveness in proportion to the absorption and penetration obtained and, in
pine posts and timbers, this has been shown to be considerable. Th- ntu-re
of the preservative is such that the treatment cannot be expected to have
the effectiveness of creosote im.pregnation in material that must be in contact
with the soil or water but in emergencies, and particularly in places rmcote
from pressure treating plants, the Osose treatment warrants consideration.
The chemicals of which the Osmose preservatives are made, however, like .:ost
other preservative che..icals, are available in limited quantities ana this
restricts the extent to which treat-ment by this m..ethod can be expanded.
The steeping process.--Merely soakii., green or dry wood in a he ted
or urnhcated water solution of preservative salt for a week or two, is .iuch
m..ore efficacious than is com..only supposed. Its usc, of course, depnds on
the availability of preservative salts and its value is primarily in places
remote fro:. pressure treating plants or for quantities of material too ..:al
to interest such plants. 'When m.ercuric chloride is applied by this etho,
remarkable results are sometimes obtained and very good results have been
obtained with zinc chloride and sodium. fluoride, as is shown in the 1942
report of the ComL.ittee on Post Service Records (1).
Oil-salt co..,.bination for poles.--A pole treating method that has
had some use in recent years is to apply full length pressure treatment with
a salt preservative then, with or without subsequent sensonin. to apply a
hot-and-cold b;th creosote treatment to the butts. This serves to oconc..dze
on creosote as well as to provide a pole that is "clean" nbove the ground
line. T. process ,,p ears to have considerable merit and for some uses it
jutlfies careful consideration.
There are various other methods of treatment that m..ight be :.ention-
ed (i.3) iivn'.ludinr several of the Boucherie type, that can sometimes be
used in m em.,ergency or nuder special conditions, but it seems unnecessary to
catalo -ae them here.
Thec foregoing discussion has forecast that the a:.ount of creoa-te
produced in 19q2 for wood preservation from: domestic sources will co1
stocks that the amount of domestic creosote available for use in 194"' not
exceed that of 1941. If the authorities decide that the military needs per-
;it, enough foreign oil can be i.iported to supply all requirements not .Ot
by domestic production. This is strictly a problem of war-tiL. cono0icC,
however, and what the decision will be only those .in control can dct'. ,ir .
Th, preservative salts in co:i;.,on use or that Light be used rk: ;.:11
of i..ore or less limited availability. Zinc chlori-de s.ee .s least likely to
be seriously restricted but not one of the.i will be available in unli-ited
quantities and it should cause no surprise if any or all of the:- s1lould be
less available for wood preservation in 1942 than in 1941.
Th1 only toxic preservative that, at present, see.-s likely to be
Lore available in 1942 than in 1941 is pentachlorphenol. Extenders for cre -
sote ind solvents for pentachlorphenol, either in the form;i of ordinary
fuel oils or aromatic byproducts of petroleum cracking processes see:-. likely
to be available in any quantity thLat ;.ay be needed for wood preservation.
An.ong the substitute materials or practices that seen .ost oro_.is-
ing today for iin.ediate use if needed for large volu,.e treatinW re uire ents
are the following: use higher percentages of petro-leu. or tar in creosote
solutions, raise the lin.its on the percentage of creosote distillation
residue above 355C. where such li..its have been -set up, and use penta-
chlorphenol in petroleum. solutions. Obviously the practicability of these
and other methodss will vary considerably in different places and circumstances
and nay be upset at any ti:.;e by new developments. There is also the os@iil-
ity that the need for then. ..ay be largely avoided by a reduction in the a_.ount
of ti.-ber to be treated,
Th.. results of adversity are not always evil and not infrec- tly
the things w'e are forced to do against our will have unexpectedly beneficial
results. The research for substitutes should broaden the knowledge of is
all and we -.ay find that so..e of the substitute .materials or .mthods will
prove economical and desirable for continued and even epaniiding use under
the highly competitive conditions that we all expect to exist after the
present emergency is over.
Refere_-,,,, 01 tred
(1) A;erican Wood-Preservers' Association Report of Co -Attec, "ole:, "<-
Pressure Tr at..ent, A.W.P.A. Proc. 1942.
(2) A1-ierican Wood-Preservers' Association Report ,of CoT-_-ittee on Tic Service
Records, A.7.P.A. Proe. 1941 (and earlier)..
(3) Anon. Methods of applying wood preservatives, Forest Products Lab:r:--
tory Mimeograph R154, 20 p., 1940.
(4) BatcEan, Ernest and R. H. Baechler, "Sox.e toxicity data and their
practical significance", A.W.P.A. Proc., 1937, p. 91-104.
() Bollcr, E. R., "Zinc chloride-petroleu2 treatment for ties," A.'.i".A.
Proc. 1940, 361-376.
(6) Carsxell, T. S., and Ira Hatfield, "Pentachlorphenol for wood pr.serva-
tion," Ind. and Eng. Che:. 31, 1431-35 (:iov. 1939).
(7) Carswell, T. S., and H. K. Nason, "Properties ond uses of pentachlor-
phcnol," Ind. Pnd Eng. Chei. 30, 622-26 (June, 1938).
(8) Gordon, Aaron, U.S. patent 2,149,284, March 7, 1939 and earlier patents.
(9) Ha er, Bror, "Prcservation of wood with the Bolidcn preservative co..-
posed of difficultly soluble arsenates," A.T.P.A, Proc. 1941, 45-53.
(10) Hatfiold, Ira, "Toxicity in relation to the position and nu,-.ber of
chlorine atois in certain chlorinated benzene derivatives," A.J.P.A.
Proc., 1935, 57-66.
(11) Hulnt, G.M. and G. A. Garratt, "Wood Preservation," 450 pages, Mc-rav'-
Hill Book Co., 1938.
(12) Hunt, G.M. and T. E. Snyder, "An international ter..ite exposure test,
A.W.P.A. Proc. 1932, 282-297.
(13) __________"_____An international tcr...ite ex-
posure test," results reported annually in A.W.P.A. ProcB930 to date.
(14) Helph nstine, R. K. Jr., "Quantity of wood treated -.nd preserwvtives
used in. the United States in 19*0,": A.W.P.A. Proc. 1941, 10-432.
(15) Hydro-Electric Power Co..i.ission of Ontario, "Grounj line preserv tion
of xood puol r,t" The -bulletin, June, 1939.
(16) Johnson, R. A. "Prcservation of wooden poles, i..:prcgnated sawdust
coll r i.iethod, Electrical E., in.er -nd 1ierchaadiscr (Australia)
April 1i), 19D-0, 17.
(i17) Lu..sdin, G. and A. H. Hcarn, 'Greensalt treat-ient of poles, "A.,P.A
(18)) MacDonidd -. H. "The place of trcited timber in hih.',': construction"
A.'. P.A. Proc. 1939, 154-159.
(l9) Mc'..; r.n, C.-M.Hill, and F.C. Koch, "Greensalt -- a new preserve tivo
for weood", A.W.P.A. Proc. 1942.
(20) :-:itional Door Manufacturers Association, "MIini..u..i standards for ...il-
work preservatives" (ii.L.eo r.:h) My 21, 1935.
(21) Putt, J. W., U.S. patent 2,207,552, July 9, 1940.
(22) Heid, J. J., "A study of several products of Disco-type, low-tr.crature
coal tar as wood preservatives," A.p.P.A. proc. 1942.
(23) Voorhies, Glenn, "0il-tar creosote for wood preservation," Ort
(24) Wirka, M.., "Co;.parison of preservatives in Mississippi fence 1ost
study," A.W.I.A. Proc. 1941, 765-378.
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