Iowa County democrat. [volume] (Mineral Point, Wis.) 1877-1938, 1905-04-06
Treatmens that Weaken Timber.

oAAAt MANI 'AaL pay
Treatmens that Weaken Timber
The bureau of forestry had in oper-
alton at the st. Louis exposition an
J experimental plant for testing the in
tiuence of preseryatives upon the
strength of green and seasoned tim.
Der. Most processes involve three
stages-a preliminary treatment to
hi the wood for the next one. the ac-
tual introduction of chemical agent
and an operation which tends to seal
the pores. Thus, steaming Is some
times resorted to as a preparatory
measure. The two chemicals to
which the most attention was given
were creosote and chloride of zinc. A
press bulletin recently issued by the
bureau gives some details about the
methods followed in conducting the
inquiry and the conclusions thus far
reached. To render the COMPARISONS
as instructive as possible, the 11-foot
ttmbers with which the experiments
were made were taken from the same
forest
Because of fears that defects Of
brlttleness of treated timbers might
not be shown by the ordinary tests
under slowly-applied loads. provision
was made for both that class of tests
and others in which there was sud
den blow or impact. The test pieces
were subjected to crosS-bending strain.
compression along the grain under
both slow pressure and impact condi-
tions. The data taken include the
moisture conditions. specific gravity
and rate of growth. Durino the treat
ing operations records wer kept of the
temperature to which the timbers
were subjected to all stages. the
amount of water lost or gained. and
of the amount of preservatives absorb
ed. as Indicated by gross weight and
subsequent chemical analyses of the
test pieces.
While this program is not sufficient
" advanced to allow the drawing of
final conclusions, yet the preliminary
results are fairly indicative of what
may be expected. II is found thai
the steaming process weakens the
resistance of the wood fiber to both
steady pressure and impact loadings
II may be stated that this diminution
G. Strength is very nearly in direct
proportion to the length of time that
any given steam pressure is appli a.
The elimination Of strength was found
to be 20 percent after a pressure Ct
70 pounds was applied for 10 hours
tog reen lobolly pine and to per cent
when pressure of 90 pounds was ap-
pie dior four hours. This diminution
OF strength increased very rapidly
When hhe pressure rose above 90
pounds, and amounted to about Is
per cent when a pressure of 80 pounds
was applied for four hours.
Ii Will be easily seen that when the
conditions of time and pressure are
made very severe the conditions pre-
Vailing in pulp mill industry win be
approximated. Evidently it is well to
avoid, when possible the use of
these preliminary steaming opera
lions in the wood preserving industry.
With relation to the effect of pres
ervatlOu themselves the latter is dis
tinct from the preliminary process.
II may be said that the treatment with
zinc chloride does not seem to further
reduce tile strength of timber beyond
the effect of the steaming process.
This might have been expected when
II is considered that the strength of
the solution ordinarily used does not
exceed 2l2 per cent The strength ii
timber that had been treated with the Z
81. per cent solution of zinc chloride
after having been steamed four hours )
at 20 pounds pressure was the same
as that of timber which had been
steamed without the subsequent ap- .
nlication Of zinc chloride. The same
statement way be made of timber 1
treated with an So Ner cent solution
Of zinc chloride. 1t may be that sub
seqUently the crystalization C ~ /.
salts will weaken the wood fiber This
remains to be determined
The effect of the creosote appears
TO be the same as that of an equal I
amount OF water in weakening the 1
hber That is TO say the strength Of i
creosoted timber is that of green tim \
Der. The difference is that while green /
timber gains strength upon seasoning.
the cre0sote oil remains in the wood
and it appears from analysis of nile 4
35 years old that the oil remains in a
f"rid condition, Consequently com
nari-on between seasoned timber and
creosoted timber will always result to
the disadvantage Of the latter as far
rs 'ts strength Is concerned In the6
case of creos1ted wood. II also re-
mains to determine what changes
in the wood iber take place through ]
lanse # time in the presence of creo-
sote oil
20 Ouch Sion that" ypIleoE