C SOUTH
F O R E S T SERVICE
U. S'DEPARTMENT OF AGRICULTURE
P. 0. BOX 245, BERKELEY, CALIFORNIA 94701
A
DURAB
TY TEST
OF WOOD POSTS
. . . third progress report
USDA Forest Service
Research Note PSW-260
19721
untreated posts were exposed for 10 years. Except
with two coniferous species, the treatment did not
lengthen service life enough to be judged worthwhne.
Oxford: 831.51:841.25-841.12eU:841.42:(969)Retrieval Terms: fence posts; Hawaii; service life;
preservative treatments; stake tests.
,
Roger
G. Skolmen
In September 1961, an exposure test of round
fence posts of 10 species of IidawGi-goynwood was
setup in M a ~ k iValley,Honolulu,Haw&. The test
compared untreated posts with posts treated full
length in tanks with copper chromate-copperarsenate
by the double-diffusionprocess.'
Results of this test were last reported in 1965.' At
that time 15 of the original 205 untreated posts and
181 of the original 254 treated posts rem~ned.In
September 1971, after 10 years of exposure,only one
untreated post-a robusta eucalyptus-and 69 treated
posts rem~nedin the test (table I). Among the
treated posts, only one species-sugi-has had no
failures.Except for sugi and Norfolk-Island-pine,
data
on average life are now complete for the treated
posts. The data on average life of the untreated posts
were reported ear~ier.~
The untreated posts had an average life of from
less than 1 to 3 yeas, depending on species.
Treatment more than doubled the average life of
robusta eucalyptus and silk-oakand at least tripled
the average life of the other species.Except for sugi,
on VVkich we must reserve judgment,it is certain that
some alternative preservative treatments would yield
better result^.^ For example,ohia and robusta eucalyptus pressure treated with chromated-copper arsenate and pentachlorophenoland reported on after 5
are all still sound after 9 years.
years of exp~sure,~
The double-diffusion method of treatment has the
advantage of relative simplicity and can be done on a
farm or ranch. But it is not a low-costoperation. In
1961,treatment cost ranged from $0.30 to $0.82per
post, depending on the species treated and its ease of
debarking.
Since the geatest cost in fence buil&ng and rep&r
is transporting and installing the posts,not the cost of
the posts, the fence builder should use posts that will
last as long as possible. Though the double-diffusion
Table 1-Condition of round, 3- t o 5-inch Hawaii-gown wood posts, untreated and preservative treated with copper
chromate-copper msenate by double-diffusion, MakiM Valley, Honolulu, Hawaii, September 1971
TREATED POSTS
Bluemm eucalyphs
(Eucalyptus globu Eus)
Bruhbox
(rPFistania covlferta)
Longleaf casuarina
(Camarina glauca)
Norfolk-Island-pine
(Arau caria excelsa)
(Phia-lehua
(Mebvosideros collina)
Robusta eucalyptus
(Eucalyp fus ro busta)
Saligna eucalyptus
(Eucalyp hr s saligna)
Silk-oak
(Grevillea ro busfa)
Sugi
(Qyp tomeria japonicd
Turpen tine-tree
(Syncarp ia glom tslifera)
UNTREATED POSTS
Bluegum eucalyptus
(Eiccalyphks globulus)
Brushbox
(Tristania confevta)
Longleaf casuarina
(Camarina ghuca)
Norfolk-I sland-pine
(Arau caria excelsa)
Ohia-lehua
(Me2rosideros collina)
Robusta eucalyptus
(Eucalyphs robusta)
Sdigna eucalyptus
(Eucalyp&s saligza)
Silk-oak
(Grevillea ro busta)
Sugi
(&2.yptomeviajaponica)
Turpentine-&ee
(Syncarph glomulifera)
-
3.5
0
88
12
0
1.9
'source: Baechler, R.H., and Gjovik, L.R. The chemical analyses of posts of Plawaiian species treated in tanks by
double-diffusion. U.S. Forest Sesv. Forest Prod. Lab. 4 p. 1962.
2 ~ v e r a g elife is when 60 percent of posts were removed; if less than 60 percent, but more than 10 percent were removed,
asterisk indicates estimate was made from figure 3 in MacLean, J.D. Percentage renewals and average life of railway ties.
U.S. Forest Sew. Forest Prod. Lab. Report 886. 1957.
Round posts of 10 Piawaii-flown species were set up in MaiFiki V a l e ,
Honolulu, in 4961, top. Some posts had been @eated with copper
chromate-copper arsenate by the double-diffusioa process. After 10
years, bottom, only a few posts remain. The missiw posts broke o f fat
pound level h r n decay or termite attacks, and were ~ m o v e dAnother
.
w o d durability test undeway is shown in the background.
method was better than no treatment for the eight
hadwood species tested, its use would be u n w l i ~
when still. better treatments are avdaMe at not $00
great a &fference in cost.
It is possible that the softwmd posts-m@ and
Nosfolk-lslmd-pine-are outlasting the hardwoods because= the fun@ that attack them are less residant to
the horgmic presewatives used thm are the hardwood-destroying fungi.6 If such is the case, better
results mi&& be achieved by uGng the same process,
but with &fa"enenk chemicds.
It is noteworthy to compare temite attack, by
treatment and tree species. The subterranearn termites
(Coptolermes fomomnu~)attacked Muegum, silkoak, and robusta heavay whether the posts were
treated or not, ~ o u g lthey
l
were somewkt deterred
by the presemtives. So fa-, termites seem Lo be
avoi&ng treated Norfolk-Island-pine and sugi. W e n
untreated, these two were the species most heavay
attacked. This difference is prharjlly only of aca d e d c hterest because abterranean termites are not
yet an jllmpr.lant h e a t to fence posts on most farms
md ranches in Hawaii. They have not yet spread that
far from. their centers of introduction.
NOTES
'~,e&ler, R. N.,How to treat fe~ace posts by doublediffusz'on. U.S. Forest Sew. Forest Prod. Lab. Rep. 1955, 6
p., illus. 1962.
2 ~ k d m e n , R. G. A durnbiliq test of wood posts in
Hawaii. . .second propess repork. U.S. Forest Serv. Res. Note
PSW-91, Pacific SW. Forest & Range Exp. Sta., Berkelley,
CdEf. 3 g. 1965.
3 ~ k w 9.
, O., and J. W. Kulp. SePvice mcords on *eoted und
un8rested fence posts. U.S. Forest Sew. Forest Prod. Lab.
Res. Note FPL-068,52 p. 1964.
"Skolmen, W. G. I"reservalives extend sewice life ofohia and
robus& posts. U.S. Forest Serv. Res. Note PSW-171, Pacific
SW. Forest & Range Exp. Sta., Berkeley, Calif. 2 p. 1968.
'~kdmen, R. 6. i"uea8ing costs and dumbility tests of
Hawaii-gown wood posts tresfed by double-diffusion. U.S.
Forest Serv. Res. Note 198. Pacific SW. Forest 8r. Range
Exp. Sta., Berkeley, Calif. 5 p. 1962.
'Baechler, R. H., and H. G. Roth. The double-diffusion
method of IPeating wood: a review of studies. Forest Prod. .I.
14(4): 171-176. 1964.
ROWR 6;;. SKOLMEN is on the staff of the Station's Institute of PacMc
Islands Forestry, with headquarters in Honolulu, Hawaii, where he has
h e n hvestigdhg the uses, properties, and processhg of forest products.
Native of San Francisco, he holds B.S. (1958) and M.S. (1959) degrees in
forestry from the Universiw of Calgor~nia,Berkeley.
U.S. Forest Service research in Hawaii
is conducted in cooperation with
avision of ForesLry
Hawaii DeparLment of Land and Natural Resources
GPO 981-791