U.S. DEPARTMENT OF AGRICULTURE • FOREST SERVICE • FOREST PRODUCTS LABORATORY • MADlSON, WIS. 

U. S. FOREST SERVICE

 RESEARCH NOTE

 FPL-068

 December 1964

SERVICE RECORDS 

ON TREATED 

AND UNTREATED FENCE POSTS 
The Forest Products Laboratory is maintained at Madison, Wisconsin, 

in cooperation with the University of Wisconsin. 
SERVICE RECORDS ON TREATED 

AND UNTREATED FENCE POST1 

By 

J. OSCAR BLEW, JR., Technologist 

and 

JOHN W. KULP, Technologist 

Forest Products Laboratory, Forest Service 

U.S. Department of Agriculture 

Summary 

This is a progress report on service tests of fence posts, untreated or treated with 

preservative, conducted either by the Forest Products Laboratory and other branches 

of the U.S. 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 preservatives and method of treatment reported in table 2. 

This Note is a revision of Forest Products Laboratory Report No. 2005 of the same title, originally 

published in 1954, and revised in 1959. 

FPL-068 

1 
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 fence posts were started in 

cooperation with various agricultural experiment stations in 1908 (4). 2 With the 

establishment of the Forest Products Laboratory in 1910, these studies have been 

gradually expanded. Service tests on fence posts are a simple and convenient means 

for comparing the preservative value of different chemicals and the performance of 

the numerous methods by which the chemicals can be applied (3 ). 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. 

A list of other sources of information on post service records will be found in the 

appendix of this report. Space does not permit a presentation of complete details on 

the treatments or on the properties of the various preservatives 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 widely in the different test 

areas. In some installations such as those in Mississippi and Louisiana, conditions 

are highly favorable for decay and termite attack. Termites are seldom found, 

however, in the northern test areas such as those in the States of Wisconsin, Minnesota, and Montana. In the northern States, temperatures throughout the winter months 

are not conducive to rapid decay. 

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 advantages 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. 

Underlined numbers in parentheses refer to Literature Cited at the end of this Note. 

FPL-068 -2-

2 
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 fence-post 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 treatment. Posts were 

generally debarked except where noted or where treated by the tire-tube and enddiffusion processes. 

The test posts have been inspected at various times, usually at regular 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.” 

Methods of treating fence posts are described in “Preservative Treatment of 

Fence Posts and Farm Timbers,” U.S. Department of Agriculture Farmers’ 

Bulletin No. 2049 (4 ). 

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 performance. It is also possible through the 

use of mortality curves developed for crossties (6) 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 averagelife 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 

FPL-068 -3-
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; namely, (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 percent copper) solution, 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 averagelife of 8.4 years, and 12 years when 

the butt portion is brushed with water-gas tar. Engelmann 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 (2 ).--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 creosote from 1 to 45 hours lasted, on an average, 

FPL -0 68 -4-
11 to 23 years. Posts treated with light fuel oil solutions containing coal-tar creosote, 

pentachlorophenol, and copper naphthenate are shown for tests located in Illinois, 

Mississippi, Missouri, New York, and Wisconsin since 1942. During this period of 

21 years or less, some of the post species have not had an opportunity to show the 

length of service they may be expected to have. All have shown an improvement over 

untreated posts of the same species, however. Posts, such as pines, black cherry, 

Douglas-fir, white fir, hickory, and oaks have been in test for periods of 16 to 21 

years. When seasoned and treated with soaking periods of 48 hours or longer, these 

posts generally can be expected to last approximately 20 years or longer on an 

average in Illinois, Missouri, and Wisconsin. In Mississippi, slash pine posts soaked 

48 hours in pentachlorophenol solution and with somewhat higher than normal preservative retention for pine posts, will probably last longer than 20 years on an 

average, and red oak posts at the same location show an estimated average life of 

19 years. Posts of aspen, birch, ash, maple, sweetbay, tamarack, sweetgum, and 

tupelo 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 

little or no improvement with balsam fir and tamarack posts in that State. 

Double diffusion (1) .--The double-diffusion process consists of successively soaking 

green-peeled posts in chemical solutions that diffuse into the moisture of the wood 

and react with each other to deposit a preservative 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 5 posts have failed in 22 years. Later installations of 

southern pine posts with various chemical combinations have been made in Mississippi, Alabama, Georgia, and Tennessee. After 7 to 17 years of service, an average 

life of from 6 to 26 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 differences 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 such as 

willow and yellow-poplar appear to show more promising results, particularly with 

higher retentions and with full-length treatment. 

FPL -0 6 8 -5-
Lodgepole pine and Douglas-fir treated with copper sulfate-sodium chromate have 

shown poor performance during 9 to 10 years’ service in Washington and Oregon but 

have shown up much better when treated with sodium fluoride-copper sulfate. 

With 3 years’ exposure of posts in Hawaii, results with sugi and araucaria are 

promising, while early failures have been noted with brush box, casuarina, blue gum, 

eucalyptus robusta, silk oak, and ohia. 

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

are allowed to stand upright for several days in a 15 to 20 percent solution of zinc 

chloride or other water-soluble wood preservative, Following the application to the 

butt end, the tops of the posts are given a somewhat shorter application in the same 

preservative solution. Of the posts treated by end diffusion, 6 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 24 years, or from 10 to 

15 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 17 years for slashpine 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 satisfactory 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 groundline, have a life of 3.7 to 7.5 years in Wisconsin, Southern yellow 

pine posts treated with Osmo-plastic 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 watergas 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. 

FPL-068 -6-
Hot-and-cold bath. --Approximately 135 installations of posts treated by the hotand-cold-bath method, involving 47 different species and 9 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 in the case of the pine 

and to poor preservative penetration at the groundline 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. 

3 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 averagelife of 17 and 19 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 8 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, 36, 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. 

3 

-Forest Products Laboratory Memorandum No. 63-015, “The Osmose Preservatives and Processes,” describes the Osmose method. 

FPL-068 -7-
Between 9 and 47 years of service have been reported for 57 installations 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 creosotecoal tar solution or creosote-petroleum solution. These posts display no failures 

during 37 to 47 years of service. Alsooutstanding are southern pine posts in Mississippi treated with water-gas tar and with 5 percent solutions of pentachlorophenol or 

tetrachlorophenol, which have sustained few failures during 27 years of service. 

The results noted from posts pressure treated with waterborne preservatives are 

variable. Southern yellow pine posts treated with zinc meta arsenite have been in 

service in Mississippi for 27 years with only 3 percent removed, while 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 35 years, while 

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

preservatives show an average life of 27 to 28 years in Mississippi, while several 

more recently installed have shown no failures during 14 years of service. 

Steeping (8 ). --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, that were treated with mercuric chloride, show estimated averagelife 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 16 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 (7).--Posts of ash, aspen, birch, butternut, cherry, cottonwood, maple, 

red oaks, jack pine, sweetgum, and willow show an estimated average life of 10 to 

15 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. 

FPL-068 -8-
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. 

Literature Cited 

FPL-068 -9- .5-54 
APPENDIX 

List of Other Publications Containing Service 

Records on Treated and Untreated Fence Posts 

FPL-068 -10-
FPL-068 -11-
FPL-068 -12-








































PUBLICATION LISTS ISSUED BY THE 

FOREST PRODUCTS LABORATORY 

The following lists of publications deal with investigative projects of the 

Forest Products Laboratory or relate to special interest groups and are available upon request: 

Box, Crate, and Packaging Data Logging, Milling, and Utilization 

of Timber Products 

Chemistry of Wood 

Mechanical Properties of Timber 

Drying of Wood 

Pulp and Paper 

Fire Protection 

Structural Sandwich, Plastic 

Fungus and Insect Defects in Laminates, and Wood-Base 

Forest Products Components 

Glue and Plywood Thermal Properties of Wood 

Growth, Structure, and Wood Finishing Subjects 

Identification of Wood 

Wood Preservation 

Furniture Manufacturers, 

Woodworkers, and Teachers Architects, Builders, Engineers, 

of Woodshop Practice and Retail Lumbermen 

Note: Since Forest Products Laboratory publications are so varied in subject 

matter, no single catalog of titles is issued. Instead, a listing is made for 

each area of Laboratory research. Twice a year, December 31 and 

June 30, a list is compiled showingnew reports for the previous 6 months. 

This is the only item sent regularly to the Laboratory’s mailing roster, 

and it serves to keep current the various subject matter listings. Names 

may be added to the mailing roster upon request.