+(J
'_ABORATORY
U. S. Department of Agriculture, Forest Servic e
FOREST PRODUCTS LABORATOR Y
In cooperation with the University of Wisconsi n
MADISON, WISCONSIN
MINIMIZING SHRINKING AND SWELLING O F
WOOD BY REPLACING THE WATER WIT H
NONVOLATILE MATERIAL S
By ALFRED J . STAM M
Chemis t
and
L. A . HANSE N
Senior Scientific Ai d
June, 1935
The antishrink treatment described in thi s
report is not a "cure-all-ills" process . It i s
limited in application to dimension stock ; it i s
expensive and has not been sufficiently tested fo r
recommendations regarding its use . It gives anti shrink protection exceeding that obtained by direc t
impregnation over relatively short relative humidity
change cycles, but whether the additional protectio n
warrants the additional-expense is also as yet unknown . Further experimentation is now being carrie d
on with the hope of finding a cheaper, more generall y
applicable method .
The extremely high adsorptiv e
power of wi;44 fax water makes the solution of thi s
problem a difficult one .
MINIMIZING SHRINKING AND SWELLING OF WOOD B Y
REPLACING THE WATER WITH NONVOLATILE MATERIALS By
Alfred J . Stamm, Chemis t
and
L . A . Hansen, Senior Scientific Ai d
i
Forest Products Laboratory,- Forest Servic e
U . S . Department of Agricultur e
Synopsi s
When either green or dry wood. is i i,egnated wit h
-a water-insoluble oil, or molten wax or resin, the 1mr regnating material merely enters the microscopically visibl e
capillary structure . Water in the fine swollen structur e
of the cell wall can, however, be replaced by a liquid whic h
is completely miscible with water ... This liquid if also a
solvent for waxes and resins can be replaced by the latte r
at temperatures above the melting point . This procedure ha s
been used for getting water-insoluble waxes, oils, and resin s
into the intimate Structure of the cell wall, using cello solve as the intermediate solvent . Only a partial shrinkag e
of the wood from the green condition occurs and t• subsequent dimension changes with changes in equilibrium relativ e
humidity are materially reduced . The process can thus serv e
as a coaab .ned seasoning and antishrink impregnation treatmen t
for refractory species,., Data obtained by the ordinary impregnation method, and data obtained by impregnating dr y
wood ith the waxes and resins dissolved in wood-swellin g
solvents are given for comparison .
-Presented before the Colloid Division, American Chemica l
Society, Kew York, April 22, 1935, and submitted to th e
Journal of Industrial and Engineering Chemistry for publication .
?Maintained at Madison, Wis ., in cooperation with th e
University of Wisconsin .
R1062
J
r.1t r Odtr tOlt
t
: :
Treatmeis for mini .iis ,ng t fFt W r)!T't .ent change s
and accompanying shrinking and . ue:l.Ung of woos6 that hav e
bean wAther proposled o$ suAcces
Lly applied ..fall into twro
441) .io Lsture-e clu.si tie,atr .en ,s :a cl (2) moistur retent ion treatments . The former class may be f .. +ther 4bdivided into coatinc~4 pod intrafiber treatroe ts .
Co!iin .
'taiaatments can t e . Jill further subdivided
.to extern-a l
- *oatings and 'Petal ur f ace Co. in ; ,r
External surface coatings have received •the • iiao 8
intensive study . Coatings that show a moisture-excludin g
effectiveness as high as 98 percent as compared to untreated
controls when a1 r r iat ily exposed to relative humidities o f
97 to 100 perce'-t or two weeks, 60 Descent . relative -r~ariidit y
fear two weeks, -and weather exposure for 'six weeks 'Or ptiri.od s
. of over a year have been developed at the Forest i i'ti'o4cta
Laboratory (1, 2, 3)
'these consist o f coati.4s of a re
'
leaf between c . is of other material g. such ae paints w)d
.
varnishes . Coatings of varnish, enamel, or . int cont a
aluminum powder give a noisture-excluding effectiveness of 90 percent and better . Bituminous paints, granular pigmen t
pailiti,y : and spar varnish as well as synthetic resin varnishe s
all show a good moisture-excluding effectiveness (50 to 9 0
percent) ,hen a number of coats are applied . Although thi s
means of excluding moisture in many cases is very effective ,
it has the distinct disadvantage of being dependent upon th e
coating remaining perfectly intact .
It is thus unsuitabl e
for use where the wood is subject to considerable mechanica l
;veal and tenets to lose its effectiveness under severe weathering conditions . Subsequent cutting and nailing of the woo d
immediately subjects it to moisture sorption .
I w•ou..1,d seer preferable to give the wood a treatment that woa d . .coat or . '~►,j l
el the e .n .llary structur e
as well as to coat the external suieace . Milfortunate.ly ,
aluminum power and ok f granules $gments wises 'f
th e
basis far l
is-as, 4saxi-te•u pretectfiG_ ; coatingp
a 0oo coars e
to penetrate the fibe-r v\lPities bcatYo h c
inicating
openings between ta,e ft.b • eavit ie tango.
rom abou t
0 .02 to 0 .-4 microns n diaxetet (4),
s
Impxeg%k
he,v~a bee i
i g vaxio
oil ; rss,, '•
x% egavert inn o ;1 00 . Zvi,-t-,ia i ~•ed nap •
in gasoline, molten beeswax, 4Pr~,
zloseo =
varnish under alternate vacuum and -Pr,
.*,t gav}c ` ~
' r
moisture-excluding efficiencies over
all
l
n
'
55, and 63 perc U
i
merely surface coated wigiANP
brush coatings, better mTAOIMOf
by impregnating with the of sue':
face coatings are less thoroughly formed than the surfac e
coatings . One perfectly intact thick film seems to be superior to innumerable less complete thin films . The foregoin g
moisture-excluding efficiencies of impregnated wood are als o
liable to be considerably less over longer exposure periods .
MacLean ,l immersed paraffin-impregnated blocks of wood in wate r
'-MacLean, J . D . Unpublished Forest Products Laborator y
report 8-4 M22W (1928) .
and followed their dimension changes and increase in weigh t
with time over a period of more than a year . In all case s
the treated specimens swelled as much as the controls but i t
took 3 to 4 times as long to attain equilibrium .
Some work has also been done on minimizing dimension changes of wood by retaining rather than excluding th e
moisture . Treatments with sugar solutions (3) and with concentrated salt solutions are of this type . One of the author s
has shown (5) that wood impregnated with strong salt solution s
ti.vQ h:uaidoes not start to shrink until the prevailing r
dity is equal to the relative vapor pressure in equilibriu m
with the salt solution . For example, if a block of wood i s
impregnated with a solution of magnesium chloride of a concentration that will attain saturation before the wood i s
dried to the fiber-saturation point, shrinkage will not occu r
until the equilibrium relative vapor pressure of the syste m
falls below 33 percent . In many localities this may neve r
occur so one right say that this treatment affords complet e
antishrink protection . This is, however, not the case as a t
high humidities the block will absorb so much water that i t
will tend to drip from the surface and carry salt with it .
This may continue until virtually all of the salt has bee n
lost . The block then loses its antishrink properties whe n
again dried . This difficulty could be avoided by originall y
drying the block to a moisture content slightly below tha t
at which shrinkage commences and applying a surface coatin g
that would be pervious to water but not to salt and whic h
would not loosen from the surface under the osmotic actio n
which would result . It is questionable, however, if such a
coating material exists . Treating the wood with a les s
hygroscopic salt, such as sodium chloride, would materiall y
R106
reduce the dripping tendency at high relative h zmi=di i :es..
A sodium chloride treated specimen would, however, start t o
shrink at 75 percent relative humidity, so that the anti .shrink protection would also be reduced :
When wood is treated with water-solu :kple a ter i
such as salts and sugar, the solute diffuses into the water
in the fine capillary structure of the wood within whic h
swelling takes place, thus gi r .ng an intrafiber treatment .
A salt solution will, in fact, attain
concentration withi n
the adsorbed water virtually the sarne,fn the bulk water ('2) ,
When the water is evaporated the salt will depoeit in the
cell wall, cutting down the total shrinkage to twee oven-a y
condition by are
k .
to the volume of atilt deposite d
(5) . If a water-insoluble material could be depot} ted w=itl n
the cell walls in . a similar manner, it would very lilely
have an appreciable effect upon the subsequent shrinking and
swelling and should have none of the inherent disadvantage s
introduced by wotAg 'ekatt ai_ luble materials . Ir pxegnati.on
of either green or dry wood with water-insoluble matetial :s ,
however, results merely in the penetration of the microscopically visible capillary structure . Water-ira_, otmbl e
materiels which don
well wood tnw
A .
cell walls of wood only by diffusio, inIe wood-swelli n
solvent which is adsorbed by the w©oda o ly the metho d
replacement in•which water is replaced by a oes&ft
_
in succession each of which is completel y
following liquid (6) .
Exile '
+
nl
:l
-
'
Le '
This paper is an introductory surrey of i t ,Pbfiber treatment of wood with water-insoluble materials usin g
the replacement and diffusion methods . The effective'nes s
of retarding the shrinking and swelling of wood obtaane : with
these treating processes is compared with the ffle'ctivenes s
of total surface coatings obtained by direct i,rri,Vre•nation .
The treatments were made on small wood blo ,e3 o f
white pine heartwood approximately 9 by 2 by 2 cma T ht Fon g
dimension was in the tangential direction . A 4044 :d4tm alision
in the fiber di eetic was chosen in order t4 e1 .r .iw factor of penett tiox . The results thus shell,
€ilim
eff (Ft,
under complete it pelegn ,tion conditions . Them ge . , ,r at
least . in their present state of development, a.. e r :a*
s-p. e4**8 e
able for treating large specimens of ref afcte
effectiveness of reducing the shrinking and . }1 a g of rloeTLY
p
R1062
- .-
a
less .
forms of dimension stock might ve-117 e_ll be co+ sti . *h
than the values given in this
4er t most
3 vow:.
drastic treatmen_td• .. End--gr-aia laaak flooring and ,ethe r
similar forms of Mall diensotaak, l owever, fall TAM:
within the realm of treating by these methods .
Air-dry wood with a moisture content of 16 pE*:uen t
was chosen as the starting material . The swel .l *g of tt .
blocks given in all the following tables ale'
s c~ dition .
r
Replacement Proces s
In order to make the replacement p=re a
s?nupl e
as possible, it is desirable to use a single inta -tle c t o
replacing liquid whic;ii is completely mis. ible with Water a%d
with the water-insoluble material that is to be depcisite d
within the cell wall . The liquid should al*'o 12,4il above t.d
boiling point of water to facilitate its re0:41nt nt o f
water . Cellosoive (ethylene glycol monoethyl e-tlile
was
to
found to be an ideal solvent for this purpose I(bsu,.
136° C .) and was hence used for all . the xOP100utO giWE is
this paper .
It is completely miscible with w*t
at . U
temperatures and with various waxes, oils, ai .•
' 's wt
only reasonably elevated temperatures . Table 1
v
temperature above which the various impregnatizIg a ,t6 i.+ :
used form a solution with cellosolve in any pr ar y l® .:s .
The effect of adding small amounts of water to solut -omo o f
beeswax in cellosolve was determined . Complete miseii ,lit y
was obtained when 3 percent of water was added to a solutio n
of 5 percent beeswax in cellosolve .
Separation into two.
layers resulted when 5 percent of water was added . The lei
water tolerance of the system thus makes it imperative tha t
the replacement of water by cellosolve be quite complate .
lla°
0 e .The blocks were weighed to 0 .01 gram and t
sions determined with a micrometer caliper with a4 bceE alo y
of from 0 .002 to 0 .003 cm . The blocks were the* s-o• i i n
tl e
water in a vacuum desiccator, the air being removod Tro
blocks by alternate evacuation and releasing of the ra uAm .
This procedure brought the moisture content considerabl y
above the normal green condition . This was done to make th &
replacement conditions uniform and as severe am r kit *PINS
'4 ,
g
be encountered in practice .
The blocks were them wcAef
measured, and soaked in cellosolve, the volume of cellosolv e
used being about twice that of the water contained in th e
blocks . After soaking for about a week the water was distilled off under a vacuum of about 60 cm . of mercury (temperature 40° to 45° C .) .
Table l .--Temperaturesabove which the impregnatin g
materials aresoluble in ' cellosolve in
all proportion s
Material
Spermaceti
Paraffin
Beeswax
Stearin
Stearic acid
Halovax
Rosin
Linseed oil Tung oil
: Approximate ▪: Temperature o f
complete
: melting
▪
miscibilit y
f
point
:
;
13
57
68
58
58
90
85
:
50
87
70
5
60
90
19 5
0
---20
1Soluble at room temperature, minimum point o f
complete miscibility not determined .
R1062
_6 -
The distillation was carried out in a number o f
steps, each a day apart, in order to insure complete outwar d
diffusion of water and inward diffusion of Gellosolve .;
About 20 to 30 percent of the total volume was distilled of f
each time and an equal volume of fresh cellosolve added . The
water content of each of the succeeding distill .' e:s for a
batch distilled eight times was 58, 41, 19, 5, 1,6 , 1.3, 1 .0 ,
and 0 .4 percent as determined from the refraettVe
.,.,
cpy
di€-After the last distillation two of the blocks were
tilled on a steam bath and the water content of the tota l
distillate determined . On the basis of the dry weight o f
the wood it was approximately 0 .2 percent . The possibilit y
of a small amount of volatile extractive material in the
wood distilling over with the cellosolve and water mode thi s
determination of the residual water by refractive index a
little uncertain . For this reason a similar repla, e .ent o f
the water in cotton linters alpha cellulose by cellosolv e
was made . The residual water in this case was foulld to b e
less than 0 .1 percent . Virtually all the free -and a ;ds :orbe d
water in wood can thus be replaced by cellosolve .. This:
replacement was made without any shrinkage occurring ; in
fact, there was a slight increase in dimensions resrult .iag
from soaking of the water-swollen blocks in cellosol qe.
Although a slight shrinkage accompanied the removal o .
water, the dimensions in the dry cellosolve in general Te e
mained slightly greater than the original water-soaked di :mensions (fig . 1) .
:4
Subsequent replacements of the water with cello solve in blocks at a moisture content just below the fiber saturation point of the wood (average moisture content 25 :-1 •
percent) were carried out by heating the blocks in cello solve to 700 C . under a vacuum which just caused continu o
distillation . The total distillate obtained in 24 hour s
contained 20 percent -water, and the blocks still retaine d
3 percent of water as determined from the dry distillatio n
of the blocks . The total distillate obtained in 48 hour s
under the same conditions contained 6 .S,' percent water an d
the blocks but 0 .25 percent water, . It is thus possible t o
replace the water with cellosolve much faster than th e
replacements used in the regular measurements if the initia l
moisture content of the wood is at the fiber-saturatio n
point or less . Continuous distillation and the use o f
higher temperatures and less vacuum are also advantaoG at, :y
Preliminary measurements made by R . O . Rounds a t
the Forest Products 4 :aborat ory indicated that th,a i epla e ment of a water-soluble intermediate replacing agent by a
Rl&62
Figure 16--Volumetric swelling of white pin e
blocks from the air-dry conditio n
to different stages of the replacement and direct impregnation processes with stearin and after a
series of alternate 2-week exposures to 90 and 30 percent relativ e
humidities together with the corresponding values for the control .
a
I
I
90 30 90 30 90 30 90 30 9 0
RELATIVE HUM/O/Y
I
I
I
I
I
nonpolar liquid cannot be made so efficiently from th e
standpoint of constancy of dimensions as the original re placement (table 2) . These replacements, with the excwtion of the acetone-toluene replacement, ' were, made in a
continuous distillation-extraction apparatus in which th e
blocks were kept continuously submerged in the distillate
r .Thiswanecrystheplacingqudsbolatfew
e
temperatures than the liquids replaced . The last valu
given for the percentage retention of the sw8lli-g in weste r
was determined under the most dr .stic replacement conAitiox.s
and is perhaps a more representative value than the others .
In all cases t}a values are practically constant for th e
replacement with the different nonpolar liquids, using various replacing agents . Although all the water held below ,
the fiber-saturation point (29 percent for ttae white ytd-Nfe )
can be replaced by water-soluble intermediate rri.la.cinc
agents without accompanying shrinkage, about 19 pier sn , o f
the replacing agent corresponding to a moisture 'content o
the wood of 5 .5 percent cannot be replaced by a nompola4' '
liquid, although it can be removed in the preswappe of t
nonpolar liquid with accompanying shrinkage . It is interesting that this moisture content corresponds closely wit h
the moisture content at the inflection point in the moister a
content-relative vapor pressure curve which, in turn, i s
believed to correspond to the initial surface-bound mono molecular layer of water (7) . This surface-bound wate r
can apparently be replaced by swelling agents which have a n
affinity for the wood but not by nonpolar liquids which
themselves show no affinity for wood and cause no swelling .
After replacing the water with cellosolve th e
regular test blocks were placed in oils, molten waxes, am d
molten resins and held at temperatures slightly in eA .aea s ce
of those given in table 1 for more than a week to a : .mow t
outward diffusion of cellosolve and the inward diffusion off '
the treating material to take place . The cellosolve wa a
then distilled off under a reduced pressure at these ternperatures in the presence of an excess of wax . A Numbe r
of distillations several days apart were made to insuxq
complete removal of the cellosolve . In all of these distillations only cellosolve distilled over so that ea,c-i dis tillation was continued until no more visible condensate '
could be collected . The blocks were then weighed an d
measured an,d- placed in a 90 percent relative humidity roo m
at 80° F . All of t .e determinations were made in duplicate .
One block was kept in the 90 percent relative humidity roo m
for 20 weeks and the other for 2 weeks . . 'The latter wer e
next placed in a 30 percent relative humidity room at 80° F .
R1062
-8-
•p.
#b
•R .--Retention of the external volumetric dimension -`
change swelling of white pine in water result ink; from the replacement of the water wit h
nonpolar liquids
Replacing
material
10araOnik Pt e
:
ri
--~
:
i
Retention o f
swelling i n
water resulting
from th e
replacemen t
Percen t
Toluene
Alcohol-acetone
1.
Petroleum ether . . . . :Cellosolve
(boiling point
:
20 0 . 40' C .)
Benzene :
Do
.
:
:Diacetone alcohol . . . :
:Cellosolve
83 . 9
84 . 8
83 . 0
.8
84
83 . 5
84 . 5
81 . 3
85 . 0
81 . 3
85 . 5
86 . 3
185 . 7
' All but this value were taken from the preliminar y, stud y
made byyR . C . Rounds at the Forest Products Laboratory .
In the case of the last value, the authors carried o n
the extraction for three weeks . The residual cello- .
solve was less than 0 .5 percent as determined from th e
refractive index and from dichromate oxidation tests .
R1062
for 2 weeks and then returned to the 90 percent relativ e
humidity room . These blocks were put through five complet e
cycles after which they were placed in the 90 percent relative humidity room for 6 to 8 weeks . The blocks that wer e
held for 20 weeks in the 90 percent room were then place d
in the 30 percent relative humidity room for 6 to 8 weeks .
The dimensions of each block were determined every 2 week s
for the first 20 weeks and then again at the completion o f
the humidity tests . The retardations of the shrinking an d
swelling occurring between 30 and 90 percent relative humidity referred to the control (volume change of contro l
minus the volume change of the treated block divided by th e
volume change of the control) are given in table 3 for th e
average of four 4-week relative humidity change cycles . The
first 4-week cycle gave somewhat erratic results for som e
of the specimens, presumably because all the cellosolve ha d
not been previously completely removed . For this reaso n
the averages for cycles numbers 2 through 5 are given .
Similar values for the percentage retardation of the shrinking and swelling are given for a long cycle (20 weeks a t
90 percent relative humidity and 6 to 8 weeks at 30 percen t
relative humidity) .
The volumetric swelling of blocks of white pin e
from the air-dry condition to different stages of the proces s
of replacing the water with stearin are shown diagrammaticall y
in figure 1 together with the swelling occurring at each ste p
in the subsequent 2-week exposures to 90 and 30 percent relative humidity . Corresponding data for the control and fo r
direct impregnation with stearin are given for comparison .
for the retardation o f
Data are given in table
the shrinking and swelling of wood under various drasti c
replacement conditions . The values for no distillation s
are for cellosolve replaced blocs soaked in molten oil s
and waxes for a week . Subsequent values are for block s
from which cellosolve was removed by different numbers o f
distillations 2 days apart .
Direct Impregnatio n
Air-dry blocks were also impregnated directly wit h
the oils, molten waxes, and molten resins by immersing the m
in the liquid at about 85° C . and alternately pulling a
vacuum and releasing until air bubbles no longer appeared .
These were put through the same relative humidity cycles a s
R1062
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the blocks impregnated by replacement . The retardations o f
shrinking and swelling resulting from these treatments ar e
given in table 3 on the same basis as for the replacemen t
treatments .
Diffusion Proces s
Oven-dry blocks were also impregnated with solutions e the oils, waxes, and resins, dissolved in wood swelling solvents, cellosolve, methyl alcohol, and acetone .
The impregnation was carried on in a similar manner to th e
direct impregnation with molten waxes and resins except tha t
lower temperatures were maintained . The blocks were heate d
in the impregnating solutions for 4 to 5 days at temperatures slightly below the boiling point to promote diffusion of the solute into the cell walls . The volumetri c
swelling of wood in the dry solvents relative to its swelling in water are cellosolve 85 percent, methyl alcohol 94
percent, and acetone 63 percent . The treated ()locks wer e
dried in a vacuum oven at 45° C . after which they were subjected to similar relative humidity change cycles to thos e
used for testing the antishrink efficiencies of the othe r
treated blocks . The results are given in table 5 for th e
retardation of the shrinking and swelling obtained durin g
one 4-week cycle .
Discussion and Conclusion s
It is evident from table 2 and column 2 of table 3
that the maximum efficiencies of replacement of water wit h
a water-insoluble material from the standpoint of retentio n
of the water-swollen dimensions of wood is about 80 percent .
The value given for rosin is higher than 80 percent but thi s
is undoubtedly due to the fact that the residual cellosolv e
was not completely removed in the }r.olten rosin . Excessiv e
frothing of the . rosin made it practically impossible t o
remove the last traces of cellosolve . The relatively hig h
hygroscopicity of glyceryl monoricinoleate indicating it s
polar nature accounts for the more complete replacement i n
this case .
Replacement of water with cellosolve alone show s
no change in the subsequent equilibrium swelling and shrinkThe replacement of the cellosolve with waxes ,
ing (table 3) .
oil, or resins does, however, decrease the subsequen t
R1062
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dimension changes . The best results were obtained wit h
beeswax, stearin, rosin, and linseed oil and rosin, and linseed oil and beeswax . Rosin alone is not satisfactory, how ever, as it caused rather severe checking of the wood .
The efficiencies of the treatments on a weigh t
change basis, in general, paralleled those on a volume chang e
basis . Treatments with hygroscopic materials such as th e
diglycol oleate and glyceryl monoricinoleate, however, gav e
negative efficiencies on a weight change basis . The anti shrink effect of such materials is evidently similar i n
mechanism to the antishrink effect obtained with inorgani c
salts, the water being retained rather than being excluded .
The efficiencies obtained by direct impregnatio n
with the molten waxes, oils, and resins are less than thos e
obtained by the replacement method with the exception o f
paraffin in which case the efficiencies are practically th e
same . In the replacement with paraffin very little paraffi n
entered the cell wall of the wood as indicated by the lo w
Thi s
retention of water swelling (see column 2, table 3) .
will account for the fact that the replacement method ha d
no advantage over the direct impregnation method when treating with paraffin .
In all cases the efficiencies for retarding th e
shrinking and swelling of the treated wood decrease with a n
increase in the time of exposure to each of the relativ e
humidities . (C.olumn 4 versus 5 and column 7 versus 8 ,
table 3 .
Thij indicates that the retardation of shrinkin g
and morel ing is largely a matter of decreasing the rate o f
sorption of water rather than a shift in the true equilibrium .
Increasing the efficiency of the cellosolve re placement with waxes, oils, and resins materially increase s
the retardation of the dimension changes as is shown i n
table u- .
These data, together with the diffusion data give n
in table 5, indicate that it is not enough to get some o f
the treating material into the cell wall, but that the whol e
structure should be filled to obtain high efficiencies .
Fairly good efficiencies are obtained, however, by th e
simple diffusion process with beeswax and combinations o f
beeswax with other m ,te,xials when 50 percent solutions ar e
-A ma ':* w&ltile solvent than cellosolve i s
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If more highly moisture-resisting materials could
be found that would dissolve in wood-swelling solvents, t.hc
amount that would have to . be put into the wood to give goad
efficiencies might be materially reduced . Such a material
is now being sought .
r
.
The replacement process not only materially d-@ creases the dimension changes but it also causes a retentio n
of more nearly the green dimensions of wood than any o gle r
treatment (fig . 1) . The replacement process is thus of a s
great if not greater value in cutting down the degrade o f
wood due to the shrinkage occurring on initial seasoning a s
it is in maintaining uniform dimensions .
J
The replacement process as here described is unquestionably too expensive for general use . It should ,
however, be of value in seasoning and retaining the dintensions -of small expensive articles made from-refractory woods .
In the case of woods, the seasoning degrade of which is .
small, the dry wood can be impregnated with a nonaqueou s
wood-swelling solvent and the replacement carried on fro m
this stage, thus avoiding the expense of replacing the wate r
with cellosolve . The simple process depending merely upo n
the diffusion of the solute from a wood-swelling solven t
into the cell wall is not as yet in a state for recommenda tion . Because of its simplicity, further studies alon g
this -line are being made . Impregnations with syntheti c
resins under various conditions are also being studied an d
will form the material for another paper .
4
1
Literature Cite d
r
(1)
(2)
(
(
(5
(6
(7
R1062
Browne, F . L . Ind . 'Eng . Chem . 25 :835 (1933) .
Dunlap, M . E . Ind . Eng . Chern . 18 :1230 (1926) .
Hunt, G . M .
Ciro . 128, U . S . Dept . of Agr . (1930) ..
Stamm, A . J . J . Phys . Chem . 30 :312(1932) .
J . Amer . Cher. . Soc . 5b :1195 (193 4 ) .
~-
Ind . Eng . Chem . 27 :401 (1935) .
and Loughborough . W . K . J . Phys . Chem,.
39 :121 (1935) .
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