Daily capital journal. (Salem, Oregon) 1903-1919, 1908-06-18

pose the unprotected wood to fung-
Gus attack.
Ihis process. finds Its principal use
Where the amount of timber to be
treated Is too small to justify the
erection of even small treating
plant; where the land is sol rugged.
as In the building of mountain tele-
phone lines, that It is lmpractlcable
to transport the timber for even
snort distances, or where It is neces-
sary to restrict the cost of the treat
ment' to the lowest possible fagura
The Effect OF Treatment on, the
Strength of Timber.
The question Is frequently asked
whether or not the strength OF tim.
ber IS impaired by the processes ia
common use for wood preservation.
NO general answer to this can be CIV
en-, since It depends altogether upon
the character and strength. Of the
preseryative and the care with which
1t is injected. II Is probable that
creosote does not penetrate the
wood fibers, but merely forms an
external coating around them;
hence. in itself, It can not apprecl-
ably affect the stregnth of the TIM
bef. In general the ultimate
strength OF treated timber depend,
FIRST, upon the percentage of mois-
ture remaining in the wood; and,
second. upon whether or not the
wood has bsen subjected to injur-
iously high temperatures during the
preliminary processes of steaming
and vacuum II these processes were
employed. The degree of tempera-
ture which can be applied without
risk of serious injury depends upon
the duration of the temperature, the
moisture content and quality OF the
wood, and upon the pressure to
which II Is subjected.
II proper care Is observ d in the
treatment of the timber all danger
OF injury from excessive tempera-
lures can be avoided. The amount
OF moisture remaining in the wood ls
therefore a point OF greater Inn
portance. AS the moisture in a.
piece OF wood Is reduced by drying,
the strength OF the wood increases,
and as moisture Is subsequently re.
absorbed, the strength up to a GER
tain limit Is again redlced. Gre
osote retards both the absorption
and evaporation OF water; hence its
presence is thoroughly seasoned
wood exposed to humid conditions
tends TO conserve It's atrength,
wherein. on the other hand, n n Is
applied to green wood the strength
ening action of water-evaporatlon Is
retarded. Some processes tend 10
increase the moisture content OF the
wood and others TO diminish H.
Therefore whether the strength OF
timber Is increased or decreased
during creosotlng depend chiefly
upon the process employed
The effect which live steam az
safe temperatures has upon the
moisture content of'wood is now be
ing made the subject Of special
study II is safe 10 say. however.
that during steaming the amount OF
moisture I'm air-dry timber is in
creased. with consequent decrease
In strength, and that the succeeding
vacuum fails TO remove all OF the
added moisture before the introduc-
tlon OF the preservative. With many
kinds OF air-dry timber, however.
the steaming can be dispensed with
altogether, and this is done In many
commercial plants. Whether or not
! Il can be omitted with all kinds OF
wood IS not yet certain.
Those considerations, OF course,
do net apply 10 the open-tank meth
cd. or 20 similar processes where the
I timber 3 imm rsed directly in the
/ no sseryatl5e. without the pre-
liminary steamlng and vacuum. Inn
mersion in hot oil tends 10 evaporate
some of the moisture in the wood
and so TO increase its strength.
Zine chlorld and the other preser-
vatiyes which are In water solution
have a wholly different effect. Un-
less the wood structure is already
filled with moisture 10 the point OF
saturation, more water IS Injected
into It with the preseryatiye, with
the result, II the wood is partially
seasoned, of decreasing It's strength.
The original strength may be re-
\ gained, however, by seasoning. II
the zinc chlorid Is injected into the
timber in too concentrated a solu-
~ a.. .,,ov cauaa a qhQmfcal Ill -