U.S. DEPARTMENT OF AGRICULTURE • FOREST SERVICE 

FOREST PRODUCTS LABORATORY • MADISON, WIS. 

In Cooperation with the University of Wisconsin 

U.S.D.A FOREST SERVICE 

RESEARCH NOTE 

FPL-068 

1975 REVISED 

SERVICE RECORDS 

ON TREATED 

AND UNTREATED FENCEPOSTS 
Summary 

This progress report on service tests of fenceposts, untreated or 

treated with preservative, was conducted either by the Forest Products 

Laboratory and other branches of the Forest Service, or by others in 

cooperation with the Forest Service. The earliest test installations 

were started in 1908, and new tests have been added in succeeding years. 

The service records cover a wide variety of post species, 12 methods of 

treatment, and 73 different preservatives or preservative combinations. 

Actual or estimated life figures are shown for test installations where 

10 percent or more of the posts had failed at the time of the last 

inspection. Table 1 is an index to the presenratives and method of 

treatment reported in table 2. 

NOTE 

This publication reports research involving pesticides. It does not 

contain recommendations for their use, nor does it imply that the uses 

discussed here have been registered. All uses of pesticides must be 

registered by appropriate State and/or Federal agencies before they can 

be recommended. 

CAUTION: Pesticides can be injurious to humans, domestic animals, 

desirable plants, and fish or other wildlife--if they are not handled or 

applied properly. Use all pesticides selectively and carefully. Follow 

recommended practices for the disposal of surplus pesticides and pesticide

containers. 

Mention of a chemical in this report does not constitute a 

recommendation; only those chemicals registered by the U.S. Environmental 

Protection Agency may be recommended, and then only for uses as prescribed 

in the registration-and in the manner and at the concentration prescribed.

The list of registered chemicals varies from time to time; prospective 

users, therefore, should get current information on registration status 

from Environmental Protection Agency, 401 M Street, NFT, Washington, D.C. 

20024. 

The Forest Products Laboratory is maintained at 

Madison, Wis., in cooperation with the 

University of Wisconsin. 
SERVICE RECORDS ON TREATED 

AND 

UNTREATED FENCEPOSTS 1 

BY 

LEE R. GJOVIK, Forest Products Technologist 

and 

HARLEY L. DAVIDSON, Physical Science Technician 

Forest Products Laboratory, Forest Service 

U.S. Department of Agriculture 

Introduction 

The value of service tests on treated wood products in the evaluation 

of wood preservatives and methods of applying preservatives has long

been recognized. Service tests on treated ties were started by the 

Forest Service (formerly Bureau of Forestry) as early as 1902, and tests 

on treated fenceposts were started in cooperation with various agricul- tural experiment stations in 1908. With the establishment of the Forest 

Products Laboratory in 1910, these studies have been gradually expanded. 

Service tests on fenceposts are a simple and convenient means for com- paring the preservative value of different chemicals and the performance

of the numerous methods by which the chemicals can be applied. Post 

tests are also of value for comparing decay and insect resistance of 

untreated woods. 

This progress report includes records only on test installations by

Forest Service agencies or on installations by others in which the Forest 

Service has cooperated. Space does not permit a presentation of complete

details on the treatments or on the properties of the various preserva- tives used in the treatment of the posts. Much of this information is 

available, however, either in other publications or in the files of the 

Forest Products Laboratory. 

General Description of the Tests 

The records in this report were obtained from test installations in 

various sections of the United States. Soil and climatic conditions vary 

1 Recent progress reports in this series were prepared by J. Oscar 

Blew and John W. Kulp as USDA Forest Serv. Res. Note FPL-068 in 1959 and 

revised in 1964. 
widely in the different test areas. In installations such as those in 

Mississippi and Louisiana, conditions are highly favorable for decay and 

termite attack. By contrast, in the northern States, temperatures

throughout the winter months are not conducive to rapid decay. Furthermore, termites are found only in widely scattered locations in northern 

test areas such as in Wisconsin, Minnesota, and Montana. 

For the most part, the test posts are installed in boundary fences of 

farms, ranches, and units of the National Forests. Test installations 

by the Forest Products Laboratory since 1946 at Madison, Wis., and at 

Saucier, Miss., however, have been in rectangular plots with the posts

installed by the randomized-block method. The posts in plots do not 

support a fence, but for test purposes the plot system has several advan- tages over the fence-line type of installation. The posts in plots are 

exposed to more uniform soil and moisture conditions, are less subject 

to loss, and are easier to inspect than line posts. 

In many of the installations the number of posts now shown in test is 

less than the number originally installed. Losses have occurred through

the changing of fence lines, pilferage, fires, mechanical breakage, and 

other causes not associated with decay or insect attack. In such cases 

the posts have been eliminated from test. 

The posts, except in a few instances where untreated 3-1/2-foot stubs 

were used, are of usual fencepost size varying in length from 6 to 

7-1/2 feet, and in diameter from approximately 3 to 7 inches. Square 

posts, when they are used, are approximately 4 inches square, and the 

faces of the split and half-round posts are approximately of the same 

dimensions as the diameters of the round posts. Posts treated by

diffusion processes and the Osmose process were not seasoned, while 

others, unless specifically indicated, were air seasoned prior to treat- ment. Posts were generally debarked except where noted or where treated 

by the tire-tube and end-diffusion processes. 

The test posts have been inspected at various times, usually at regu- lar intervals by representatives of the Forest Products Laboratory or by

those directly responsible for the installations. During these inspections the posts are examined for the presence of decay and of termite 

attack. Posts that would break off with a moderate push, or would no 

longer support a fence because of severe deterioration in the above- ground portions, were considered as failures. They are shown in table 2 

as "removed ." 

Results of Tests 

Post service tests must be continued until all or a high percentage

of the posts have failed in order to obtain actual figures on average

life. Treated or untreated posts that have been in service for 15 years 

or longer with few or no failures, however, furnish an indication of good 

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performance. It is also possible through the use of mortality curves 

developed for crossties to obtain a good estimate on average post life 

when 10 percent or more of the test posts have failed. On this curve the 

average life is indicated when 60 percent of the posts have failed. 

Table 2 shows such estimates, or actual average-life values when all of 

the test posts have failed. 

The various post installations in table 2 are itemized and are grouped

alphabetically according to species of wood. In addition to the post

removals and average-life figures, information is shown on the preservative used, kind of treatment, and preservative retention, whether the 

posts are round, square, or split, by whom and where the posts are 

installed, the dates of installation and of the latest inspection, and 

the number of posts in test. To obtain information on various post 

species, the reader can refer directly to table 2. For information on 

various preservatives or processes, he can first refer to the index 

(table 1), which will direct him to the item numbers in table 2 relating 

to those preservatives or processes. 

Summary of Results to Date 

In arriving at conclusions on the basis of the data presented, the 

reader should keep in mind two important facts: (1) That the performance

of untreated wood used as posts is influenced by the proportion of heartwood and the soil and climatic conditions to which the posts are exposed,

and (2) that the performance of wood treated with a preservative is 

influenced by the thoroughness of the method of application and by the 

resulting retention and penetration of preservative. 

It is not reasonable to evaluate or to compare preservatives on the 

basis of results obtained by superficial applications that are known to 

result in low retentions and incomplete sapwood penetration. Even with 

the more thorough methods of treatment, poor preservative performance can 

be the result of poor preservative penetration, due either to careless 

treatment or to the resistance of a particular species to treatment. 

These factors, along with the locations of the tests, should be considered 

when evaluating a method of treatment or comparing different treatments 

and preservatives. 

Following is a review of the results obtained to date in the various 

post installations according to the method of treatment used: 

Brush-treated posts.--Untreated jack pine posts with an average life 

of 3.8 years in Wisconsin show an average life of 8 to 9 years when 

brush-treated full length with copper naphthenate (2 pct copper) solu- tion, coal-tar creosote, 5 percent pentachlorophenol in No. 2 fuel oil, 

a water-repellent preservative containing 3 percent pentachlorophenol

and 2 percent chloro-2-phenylphenol, and water-gas tar. Untreated 

lodgepole pine posts in Colorado show an average life of 8.4 years and 

12 years when the butt portion is brushed with water-gas tar. Engelmann 

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spruce posts at the same location reveal an average life of 7.1 years 

untreated and 11 years when the butts are brushed with water-gas tar. 

Cold-soaking.--This process consists of immersing the posts full 

length in unheated, low-viscosity preservative oil, usually for a period

ranging from several hours to several days. The oldest tests on posts 

treated by cold soaking were started in Minnesota in 1909. In these 

tests, elm, basswood, and red oak posts soaked in unheated coal-tar creo- sote from 1 to 45 hours lasted, on an average, 11 to 23 years. Posts 

treated with light fuel oil solutions containing coal-tar creosote, 

pentachlorophenol, and copper naphthenate were exposed in Illinois, 

Mississippi, Missouri, New York, and Wisconsin since 1942. All show an 

improvement over untreated posts of the same species. Posts such as 

pines, black cherry, Douglas-fir, white fir, hickory, and oak, when 

seasoned and treated with soaking periods of 48 hours or longer, generally can be expected to last 20 years or more in Illinois, Missouri, and 

Wisconsin. Posts of aspen, balsam fir, birch, maple, and tamarack have 

shown somewhat less improvement through cold-soaking treatment than those 

of the species mentioned above. Soaking periods of longer than 48 hours 

have, in some cases, resulted in improved service. Aspen and birch posts

in Mississippi have shown improved service as a result of incising, while 

incising has resulted in less improvement with balsam fir and tamarack 

posts in that State. 

Double diffusion.--The double-diffusion process consists of succes- sively soaking green-peeled posts in chemical solutions that diffuse into 

the moisture of the wood and react with each other to deposit a preserva- tive with high leaching resistance. Approximately 122 test installations 

of posts treated by the double-diffusion process have been made since 

1941. Of 100 southern yellow pine posts treated full length, first in 

copper sulfate solution and then in sodium arsenate solution, and installed during 1941 in Mississippi, only eight posts have failed in 

29 years. Later installations of southern pine posts with various chemi- cal combinations have been made in Mississippi, Alabama, Georgia, and 

Tennessee. After 7 to 26 years of service, an average life of from 8 to 

39 years, and possibly longer, is indicated. Many of the earlier failures 

can be attributed to low preservative retentions and to the inadequate

protection to the tops of posts treated only at the butt end. These 

factors would appear to have greater significance than the effect of dif- ferences in chemical combination, although the copper sulfate-sodium 

arsenate and the nickel sulfate-sodium chromate (with and without arsenic 

acid) appear to show up favorably. An excessively high retention of 

chemicals applied to posts from dead (insect-killed) trees provided only

limited protection, possibly due to lack of sufficient moisture in the 

wood to provide good chemical diffusion. 

Hardwood posts of red alder, hickories, red and white oaks, sassafras, 

sweetgum, and tupelo have shown up less favorably than southern pines.

Hardwoods 

results, p

such 

articularly 

as willow 

with 

and 

higher 

yellow-poplar appear 

retentions and 

to 

with 

show 

fu

more 

ll-length 

promising 

treatment. 

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Lodgepole pine and Douglas-fir treated with copper sulfate-sodium 

chromate have shown poor performance during 9 to 14 years' service in 

Washington and Oregon but have shown up much better when treated with 

sodium fluoride-copper sulfate. 

Sugi, after 12 years' exposure in Hawaii, has no failures. Brush box, 

casuarina, bluegum, eucalyptus robusta, silk oak, and ohia have average

life values of 4.5 to 11 years. 

End diffusion.--In this process the butt ends of green, freshly cut, 

unpeeled posts were allowed to stand upright for several days in a 15 to 

20 percent solution of zinc chloride or other water-soluble wood pre- servative. Following the application to the butt end, the tops of the 

posts were given a somewhat shorter application in the same preservative

solution. Of the posts treated by end diffusion, six installations were 

made in Wisconsin during 1945 and 1946, including jack pine treated with 

copper sulfate, and aspen, red oak, white oak, and jack pine treated 

with chromated zinc chloride. These posts showed an average life of from 

14 to 29 years, or from 10 to 20 years in excess of untreated posts of 

the same species. 

Five installations of posts treated with zinc chloride in Mississippi 

showed an average life of 5 to 7 years for posts of sweetbay, water 

tupelo, and sweetgum, 9 years for red oak, and 20 years for slash pine 

as compared to an average life of 2 to 3 years for untreated posts of 

these species. 

Groundline treatments.--Lodgepole pine posts with Anaconda (arsenic

trioxide) around the groundline zone had a life averaging from 18 to 

28 years in Wisconsin. The untreated tops of the posts held a fence but 

were badly rotted in that time. The results were somewhat less satis- factory on lodgepole pine and other species treated in Montana, presumably

due to drier soil and conditions otherwise less favorable to diffusion 

of the preservative in Montana. After mercuric chloride and white arsenic 

were poured in bored holes at the groundline zones, posts of various species 

installed in Wisconsin showed an average life of 8 to 10 years for box 

elder, American elm, and shagbark hickory, and 11 to 18 years for red 

oak, white oak, slippery elm, and black cherry. Jack pine posts 

treated with pentachlorophenol solution, applied in holes at the ground- line, have a life of 3.7 to 7.5 years in Wisconsin. Southern yellow 

pine posts treated with Osmoplastic at the groundline and on the post 

top had an average life of 11.2 years in Mississippi. 

Hot bath.--Posts of alpine fir and lodgepole pine treated with a hot 

bath of water-gas tar lasted 21 and 18 years, respectively, in Colorado,

and Virginia pine similarly treated had an average life of 17 years in 

Maryland. Willow posts treated with a hot bath in asphaltum had an 

average life of 10.8 years in Maryland. 

Hot-and-cold bath.--Approximately 135 installations of posts treated 

by the hot-and-cold bath method, involving 47 different species and 9 

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different preservatives, are included in this report. In 58 installations involving posts of various species treated in coal-tar creosote, 

average post life varies from 9 years to more than 50 years. Where an 

installation has had an average life of less than 20 years, it was generally butt treated in an area favorable to decay in the untreated tops.

In the case of loblolly pine, tupelo, and sweetbay posts in Louisiana, 

however, the somewhat mediocre performance was attributed to inadequate

debarking of the pine and to poor preservative penetration at the ground- line zone of the two hardwoods. Good results were noted with other 

hardwoods, some of which are difficult to penetrate uniformly. 

The results from posts treated with creosote-petroleum solution, 

pentachlorophenol solution, and water-gas tar are generally favorable. 

When petroleum oil was applied alone during the hot bath followed by 

creosote in the cold bath, the length of the post service was not so 

great as when creosote was used throughout the treatment. In 

Stoneville, Miss., variable results have been noted when various hardwoods 

have been subjected to a hot-and-cold bath of diesel oil containing 

5 percent pentachlorophenol. The results in treatment with zinc chloride 

solution in Wisconsin were less satisfactory than with creosote. 

Osmose.--An installation in Mississippi of unseasoned southern yellow

pine posts treated full length by the Osmose diffusion process displays an 

estimated average life of 25 years. Four installations of aspen posts in 

Wisconsin similarly treated show average-life values of 6 to 14 years.

Round red oak and jack pine posts installed in Wisconsin in 1946 have an 

estimated average life of 17 and 21 years, respectively. 

Pressure-treated posts.--In reviewing the test installations of 

pressure-treated posts, 43 installations treated with coal-tar creosote 

are located in Mississippi, Missouri, Montana, and Wisconsin with 6 to 

38 years of service. Of these, 27 installations should have an average 

life exceeding 30 years, and only 9 installations have had sufficient 

removals to permit an estimate on average life. Cottonwood, loblolly

pine, southern yellow pine, and sweetgum posts treated with approximately

6 pounds of creosote per cubic foot show estimated average-life values 

of 18, 22, 35, and 23 years in Mississippi, respectively, while with 

12 pounds per cubic foot sweetgum posts have an estimated average life of 

34 years. The other species should last somewhat longer. Lodgepole pine 

posts in Montana experienced an average life of only 21 years. In the 

latter case, the comparatively poor performance is attributed to inadequate bark removal and poor penetration of preservative. The creosote 

retention is not known, but is presumed to be substandard. 

Between 9 and 55 years of service have been reported for 57 installa- tions of posts pressure treated with miscellaneous preservative oils 

other than straight coal-tar creosote. Outstanding in this group in 

Wisconsin are southern yellow pine, aspen, basswood, black oak, and 

northern white cedar posts treated with either creosote-coal tar solution 

or creosote-petroleum solution. These posts display only one failure 

during 37 to 56 years of service. Also outstanding are southern pine 

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posts in Mississippi treated with a 5 percent solution of pentachloro- phenol, which have sustained few failures during 33 years of service. 

The results noted from posts pressure treated with waterborne preserv- atives are variable. Southern yellow pine posts treated with zinc meta 

arsenite have been in service in Mississippi for 33 years with only

14 percent removed; in Nebraska, lodgepole pine posts treated with a 

similar retention of the same preservative show an estimated average

life of only 20 years. Southern pine posts treated with acid copper 

chromate (Celcure) in Mississippi display an average life of 40 years,

while those treated with borax-boric acid average only 10.6 years. 

Steeping.--Posts treated by the steeping process using waterborne 

preservatives, such as zinc chloride, chromated zinc chloride, sodium 

fluoride, and mercuric chloride, have been installed in Alabama, 

Mississippi, Montana, Nebraska, and Wisconsin. Posts of southern yellow

pine in Mississippi and Douglas-fir and western larch in Wisconsin,

treated with mercuric chloride, show estimated average-life figures of 

27, 47, and 39 years, respectively. Cottonwood, red oak, sweetbay, 

sweetgum, tupelo, and willow posts treated by steeping in zinc chloride 

or chromated zinc chloride have average-life values of 4 to 10 years in 

Mississippi. In that same State southern pine posts steeped in zinc 

chloride have had an average life of 20 years. Western redcedar posts

treated with sodium fluoride and zinc chloride and installed in Montana 

exhibit no appreciable increase in life over untreated posts of the same 

species. In Nebraska, Montana, and Wisconsin, however, a significant

increase is reported in the post life of ash, cottonwood, Douglas-fir, 

elm, western larch, the pines (jack, lodgepole, ponderosa, scotch, and 

red), and willow, when treated by steeping with sodium fluoride or zinc chloride. 

Tire-tube.--Posts of ash, aspen, birch, butternut, cherry, cottonwood, 

maple, red oaks, jack pine, sweetgum, and willow show an estimated 

average life of 10 to 26 years when treated by the tire-tube method and 

installed in Wisconsin. This is significantly greater than the untreated 

life of posts of these same species. Posts of basswood, hickory, black 

locust, and white oak in Wisconsin display no significant increase in 

life as a result of this treatment, however. Aspen, ponderosa pine, and pinyon posts experience considerable added life in Arizona as a result 

of tire-tube treatment, while posts of naturally durable Arizona cypress, 

Gambel oak, and local junipers exhibit little or no increase in service 

life. 

Top application.--In treating the tops of red oak posts one-half pint

of No. 2 fuel oil containing 5 percent pentachlorophenol was applied by

inverting a jar set on a layer of felt. These posts were installed in Wisconsin, but have shown no significant increase over the life of 

untreated posts. 

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U.S. GOVERNMENT PRINTING OFFICE 1975-650-517/4 -44- 4.0-45-7-75