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i
o
March 2[
svrywEdlmoPro
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0o}iDlTl()}ssAFIrECT.|-I{GTHEMAKING0FGLUEIJ0I}ITS
ogist '
ey T . I?. TRllAX, wt"rcd Tech:rol
se:rvice.
F
o
r
e
s
t
! , c . r : , e g .pt r . . . - c i r r c l : s- I , a . b c r e , t o r y ,
t'ue
:-s u,'icrturratel;r
in the
cLces ncr:, .),r'[:'f!)';itr'r
4:;,',atthe
terra rrglued' jointrf
eiYet'ag€ lniod' tire ideas
,J.;ri+-cjl:t.Ly, a:nrl all--a-round. higl:i qila3-lty
that
of
strength'
ri'ghtiy
apply
to
strchjo1-n{;sfu}teipruperlynad.e.Thenotionofinferiorityof
glued.jointsingeneralhasdoub.tlessbeg'n,formedfronitre
pu}11n9 apart and.
of furrij-,|ure
a1]- too coillmon experience
Carelessness and
service'
Teneers peeling away in actual
abuseont}repartoftheconsumerareof.courseresponslble
forapartofthefallui"esobu.baconsiserablepartoft}re
lies
trouble
'
farther
back'
Glued producis,
if
prope:rly
m a d ' e! p o s s e s s
:- - --^^: $ srr'*Acaq!
n l r e r ar;acreir
a,rt,icies
o'ser
ati.vairtages f oi certain purposes
r l e cl d e d
so-l-id'
o f .,\r-r-L^
wood'
construction.Across-band.edplyvuood.orveneered.panel,for
examp}e,is'farmoreconstantind.imei:.sionwiihchangesof
moisturecontent,and.,especiallyin.Lirecaseof.t}rlck-core
panelsri.sLessliabletowarpand'ebangeslrape'i;hansolid'
wood'ofthesaned'j-menslo4s.fhesead'van,.;agesareofgreat
par ts er e a pr im e essenclose- fittir r g
i m p o rta n ce w h e re fl a t,
5,urt}rermore,
cabinet work, arid' doors,
dS in fur.niture,
tial,
layer s of vr oo d
b y c r o ssb a n d i n g , i .€ ., building up a} ' ber nate
at r i g h t
a n g l e s to e a ch o i h e r ,
rr v h i e h 1 s a p p ro x$ .ma -te 1 ye q u a l in str ength
wh e r e a s t h e stre n g th p ro p e rti es
the graiir,
can be obtained.
& constr uction
in all
d.ir ections,
of solid. v,r ood.,vuith and acr oss
a.re furri.ancn'!;a-L]-ycifferent.
The quality
of vrbod
us e d i n a bu i L L -r-p p rr,d u ,:f,,c an ar so be mor e exacttr - y selected
: ,
tha,n is possible in solid
c.onstruction.
AlI !he, forggo:r1g are lrenefits which the consumer
,
en j . o v s o r a !'. l e a st sl l g re s; b ut ther e ar e other s aecr ir ing par ticuiarly
to the namrfr"t*""r,
chref
of which are that
the
:
v ;c o i J . n s , 41 l e r
d i n l e n si o n s can be dr ied. mor e qui;ckly and
'But,
cheapiy and,that.i-t can be rnlre eccnoml,cally used.
offi
an d a l l ,
t n e a d 1 'a n ta g e s o f glued constr uction
t,
go for
wilr
.
n,othing it'the
ditions.
joints
a r e n o t m a d , et o w i t h s t a n d s e r v i c e c o n -
fhe glrred product must, first
of arl,
' "
faction
la t e r
u n de r re a so n a b l e se rvice;
it
give satis-'
: l
; " " '
sooner or
on top. of ilr at,
h a s g o t to w j .th sta n d. unr eascn"oi"tr ."oi;u
, . 1 ,
the drenehing,
- . , . i
, :
the s1au,
I
the punis,rnrent.
An Undeternrined. but rind,oubted,.Lyvery Grg"
:.
. . .; ; i : ,
. . :.,.
the failureg
,,:;';
part
of
.
, ..)
: :
of glued joints..are due to ir,npropergruing condi'r"
tiqns and.method,s. fleis, the u."ir"r el;irre n"|""*r,
,n*
',,,
',,"i '
'
:',"
. . , ' ;i
.i
asp e c t o f !!e q q ,tte r Wh i ch wilL be ' pr inci.pal) - y consider ed
tJ*tur*ir.rr.u '*n"
here; but it is onl-y one o{ f ive irotol"
,rrr*,
tesult,
e a ch o n q o f w h i ch cL em ands
at least.passing
. ' i .
the present
conneqtion
-2a : l
eLv
j : i
, " " ' j " i t . ' . 1
m ention in
:
Ttre Fi":e Probiens of the Manufactureq
In general,
then,
tlre problems cf the manufacturer
(f)
of glued products may be classified
as;
s u i t a b l . e ma " l e ri a i s;
of the materials
{Z i pr epar ation
': : r,s :;ructi,tn;
{3 i ;1::c:1.'et'
ctttr
(+} giuing
((t
Selection of
for use;
c cnditi ons and rnetlrods;
t h e glued stock.
\ / , ! A* v- r.r.. 1i r ', * , , f la n C c o n d l t i o n i n g
-ESI-ea-li s1-e!-Jila t er i al s
Gl '.re a n d w o o d ,ar e,
of cour se, tl:e two major pr od-
u c t s i n g l u e d . w o o d .co n struction.
The diff er ent species or -
w o o d v a ry a mo n g th e mse l ves to a mar ked"degr ee, and the several
k i n d .s o f g 1 u e , a l so ,
c h a r a d t e ri sti .cs.
It
is
ar e sur pr isingly
obvious that
should haVe an accurate and. rather
p r o p e r t i es
o f d i ffe re n t..$ oods
b e s t p r o d u e t fo r
a p a l ti cu lar
has become available
a s t o o u r n a ti ve
o t h e r p u b l i ca tl o n s
will
untike
in most
the manufactur er
conrplet.e knowledge of the
and glues if,' he is
ser vicCI.
e e
to r na$< th'
Of 1a' be year s tlr er e
a great deal of pract.lcal
ccn n e rci a"r wocr d,s;Bulletins
inforrnation
552 and,556 and
o f th e U, S. Depar tment, of Agr lcultur e
b e fo u n d . o f i n te re st
in
this
r egar d."
As to the var ious
El u e s u se d 1 n w o o d w o rk!.n g, the Sor est Pr oducts T,abor ator y
h a s i s s u e d . se ve ra l p u b i -i cations
descr iblng
t h e i ' r m o re i ro p o rta n t ch a racter istj.cs
*3-
and compar ing
A selection
Iar
rrse cannot be made until
stoca.
tr
wr-th that
glue
of the best
or wood for
bhe service
inf ornat.ion avarlable,
d e t . e : r m i - n e' ' n ' h a t ' p r o r , e r t i e s
ior
is
lhen necessary
ancl characteristics
of wood and
it
is
subjeeted.,
ncsb inportant
cha:'ac'teristics
are
of less
nerieriai
tr'or example,
shculd,
course,
quirements
on the
bird{s-eye
of the
in
of course,
imporbanee.
' r l i fi e i ^ - : r e s i s t a n c e
v;ater-resistance
characteristlcs
as white
ac'terrstics
cf
r=qr;i.rements.
lvood or glue
veneered d.oorn because of the severe moisture
+ ; o ' v ' ' h . i c hi t
th:
rlreets the
maple veneer,
different
are
a g1ue, other
ihey
hand., irl gruing
srrch a
char-
the staining
mole i.rnportant than
or maximum strengih,
of the vrood for
cond,itions
be eonsidered., but
other
In a sir:ailar
an exter-
in
and durability
selecting
glue are relativei.y
required..
are und.er-
conditions
gL'ie i:.re essetri.i-el- anc f-icrni thalt w;rat particui-ar
nros'l rrearij/
a partlcu-
is,
ilrough good strength
Te-
manner, the important
into
uses must be taken
acc ount.
Prepar?tion
Both
and stilI
preparation
the
and wood. nay be of il:.e highest
grued joints
of either
the
dlfferent
glue
cf Mg,t_er.Lef
s
exact
be inf erior,
or both
technique
liincls and brands.
glue m:-xing varies
rn mixing
-+:2h6**-
ewi.ng to the
imprcper
gluing.
for
of
quality
the
with
a prepared. glue
it
is
uFually
a d vi sa b re to folr pw
t h e ma n u fa ctu -re r, th o ugh it
the instr uctions
is
fur nished by
sometines neeessar y to var y
d e t a l l -s so a s to o b ta i n the best m ixtur e
for a par ticur - ar
p u r p o se - T h e i n o re i mpor tant points
of var iation ar e ( r )
p r ( i pu .rti o n o f d ry ma i er ials
and water , ( Z) manner of puttin g
t h e ma te ri a rs to g e th e r, ( 3) m ethod.,
speed., and tim e of
s t i r r in g ,
a n d (+) i n the case of anim al and most vegetabr e
gl-uesn temperature of the mixture.
The preparation
ting
to sl ze ,
e l i mi n a ti on
M o s ' b o f th e w o o d . th a t is
t o v e n e e r o r i n to
of wood, for
gluing
of defects"
dr ying,
to be gr ued is flr st
i n ch lumber which is later
A l t h ou g h so me sto e k th icker
invorves
cut-
and. sur facing.
cut either
in _
dr essed d.osr n .
than an inch is glued up, such
as is. used in doors, ch4ir seats, thlck
table tops, framing
f o r a u to b o d i e s, a n d , a ir plane par ts,
the fact r em ains that
the g.Teat buLk of the wood for glrring
is cut froin the 1og
i n t o ve n e e r o r i n ch b o ar ds. r ur ober
is fir st
d.r ied. and then
surfaced. for gruing, whereas with veneer
the gluing surface
i s p r o d u e e d a s i t i s cut fr om the r og
or fr i.bch and the d.ry _
ing is done afterrryards.
w o o d fo r
g l u i ng
should. be dr ied. fr ee of casehar d-
e n i n g a n d o th e r str,e sses and conditioned,
to a unifor m mois_
t u r e co n te n t.
u n e q u a r. m oistur e in the pieces befor e gr uing
is the source of much trouble afterwards,
Tlre proper
(
?t6
content
moistuTe
over quite
varies
gluing
ed- in
the
rvith
the proper
paring
also
obSects of
three
red.ucing the lumber
(f)
dimension , (Z) elirninating
is
\lnren placed
of urrlf orm thickness.
should. make complete
under
contact
to
pre-
surfaced
is
tr'or panel work it
even, and. flat.
smooth,
and (:)
defects,
Wood properly
the g1ue.
for
machin-
step is
important
the next
drying,
the surfaces
f or gluing
to be ad'd-
the amount of r.roisture
to meet.tttd
are most imPogtant.
After
ing,
conditions
of whlch the service
Upon a nwnber of . factors,
the prod.uct is
range and" depend's
a wide
together
light
relatively
surfaces
the
pressures'
ProP er Cons trr.rc t i on'
Warping,vueakness,and'lack'ofdurabilityingl-ued
commonly due to
prod.ucts
are
irnproper
construction.
ttre use of- unbalanced
governing
The rules
of .most glued,.products have bgen. pretty
through
sciously,
long
usage and by experiment.
stresses
inte:rnal
stresses
are necessarily
meiricar
arrangement
These rules,
in
the
empirlcal
skrrinkage,
of
so far
established'
well
consciously
simil-ar
as possible,
balancing
present,
plies,
or unconof
density,
and' strength
of , wlten suctr
them loy a symor parts.
laminations,
though they nay be,
-6hr
the construction
t h e y h a v e b e e n b u 1 l ' r , ? . 3 o 1 [ i d "t h e p r i n c i p l e
avoiding
ottrer
or
n?":
their
properties
of
basis
the
of var ioug Sur -
y a l t i o u s w o o d s a n cLth e g l uing char acter istjcs
R e s e a r c h h a s a l r e a d . y f u r n i s h e d a c o n S i d e r a b l - eb o d y
faces.
' o f b a s i c i n fo rma ti o n
a l -o ],tgthese lines;
the use of which
' 'nr-'Lr.i-d
help to sdve many problems of the craftsman
C o n i l i ti o n s and- M ethods of Glui4g
As previously
w 1 1 1 d ea l p ri n ci p a l l y
c e s s l t se l f,
stated, ttowever, this
w i th
discussion
the pr oblems of the gluing pr o-
w h i ch ta ke s high r ank as a Sour ce of :tr oubtr e
inVolves putting
It
a n d e x p e n se to th e ma n u factur er .
gether the glue and. wood., vrhich have been properly
in such a way as to forn satisfactory
to-
prepared,
A quantity
ioints.
and suffi-
o f g l u e i s sp re a d o n o n e or both vr ood.sur faces,
cient pr€ssur€:.is applied. to b::ing the pieces 'uogether.. If
t h e w o rk i s p ro p e rl y
sist
d o ne, the joint
which is mad.ewill
o f a co n ti n u o u s fi fu n of solid, glue fir r nly
con-
adher ing to
both rvoodsurfaces.
T h e p ri n ci p a l
de' ber mining the suecess
conditions
of the gluing process are:
or failure
t h e g l u e mi xtu re ;
(f)
Consistency of
(Z ) method of spr ead.ing gLue and quantity
s p r e a d ; (3 ) ma n n e r o f a ssem bling the lamlnatlons,
e l a p s l n g b e tw e e n sp re a d i ng of glue and pr essing;
of joining
pressure applied;'(5)
s u . r e ; (6 ) ki n d o f w o o d ; and for
perature
( 4) am ount
d.uration of ioining
animal glue,
of the room and the wood.
-72L5
and tim e
pres-
( 7) ttr e tem -
E'xperi.mental
at
ttre Forest
work has been under way f or some ti-me
Pro<iucts laboratory
irn-portance of these various
j.ng of
glued joints.
of finding
with
gluing
stated.
since
and other
conditions
p,Togress includes
used together.
the best
to cover
practice;
of
with
the
lvithin
and the work novr in
glues and wood.s corumonly
rslll
discusslon
glues,
animal
illustration
alrplane
glued lrrood prod,ucts
other
the various
The present
the v,'ork with
the purpose
uhen the scope of the investi.ga-
of factory
all
1n the mak-
w h i c h w a s d - o n em o s t l y
g1ue, covered a wide range of concitions
has been enlarged
1y to
the rel-ative
or factors
The work was started.
and the ear'l.y r'ork,
limi-tations
tion
conditions
out the best methods to use in
propellersr
animar
to determine
since
the various
be confined. large-
ihis
adhesive
poi"nts involved
offers
in prac-
tice.
The tests
types
ing
of weak joints
conditions
trated
have shown that
which may occur
or methods, or both.
in Figure
1.
The three
each.represent
three blocks
The photograph
exhibits
sets
there
are three
on acciount of poor
of ten tested, specimens
of failure
pearance
of the broken
is
in appearance and shows no distinct
crean
of g1ue.
rt
results
joints.
from
2L6
conditions.
and the ap-
The rrstarved,, type
ttre glue being
-8-
glu-
These types are illus-
glued under different
the character
maj or
film
forced
of joint
or layer
into
the wood.
!,f e L:JUf
j c i n t - b l u e t'orroci iwo a fi:'m jeiiy and the
,; appli od u a t l i n s u f f i c i , r n t tc L.ri ng rr:r'p':.:+.e
. 'riihit.c
arg arcas ef no :onte:+".
Starved joint
reeulted from tne etrpii:rtirrn r:l p:'.,-..s u r e ' f i j r i 1 o t h € g . , L u <$ra s ; t o o I i q u i d .
[,cclr- lrt t;,:;ti.,'-,
on cgrtsin rc()ic.
l)ried jcint, - girre Criod on t hs r.!ood
'*lo arp.;.iaJ. i;rrr eiina._
j c n -,J.,.1u€ t'
Fia..l
E . , , \ B l m o nt ! p , . , , i 1
t'4b331F
v , , e , r n)
uef--,;'B ,fGo::itr'
cr'o*t
over ttre edges and is
1;ures of low visco.sity
1rl'ile of joint
is
and with
due to
the
pr"ssr'-rre to giwe corprete
rat- (nioe
or'bone)
gl-ues and arises
wil]
not
likely
to
porous wood.s,
glue
jellying
contact.
gIues.
rhe
frorn the fact
oceur with
rt
n d . r i e d . t rj o i n t
that
adhere even und.er a very
The .rchirledn
without
occurs
sufficient
only with
ani-
occurs with
a d.ried. film
high
glue,mix-
of
a1r
glue
pressure.
rtant
,
In making a-glued joint
it
is of the highest im_
p o r t a n e e to h a ve th e g l u e at the pr oper
consi.stency when the
pressure is appliecl. rf it is excessively
thick or excess i v e l y th 1 n , th e re i s d .anger of getting
weak joints.
som e
v a r i a t i . o n i n co n si ste n e y m ay be com pensated.
for by the use
of a higle or a row pressure,'spread,ing, assembling,
kind of
wgod'
te ra p e ra tu re a re of impor tance chiefJ- y in r er ation
"ld
to the consistency of the glue at the exact
time of applying
pressure.
T h e vi sco si ty
m o m e n t a fte r
of gr ue at any par ticular
b e i n g sp re ad. on the wood.is deter mined. by sever-
a l c o n tri b u ti n g
ca u se s.
and the proportion
it.
of a layer
!' ir st,
ther e is
of dry material
and water used. in mixing
B ro o d a n d a n i ma l g l ues, when pr oper ly
ere quite 1ow in vlscosity,
i.e.,
m ixed and used.,
f l u i d . , v r h 1 1 ec a s e i n a n d .
-9ct {.
the kind of glue
vegeta,bt e glues
.[,rcrns of dry
glue and vrater used.
'':
'ri-ood. a,llumin glue is tliinner
than
ar larger
proportion
waod, lt
begins
at
glue has been spread
otbers.
. The total
the
surrounding
pelrd,s rrpon tkre cond.ltions
temperature
shown that
ttran the d.rying;
has relatively
at
ln
lhat
with
the
coures very
it
r,vlrereap with
great.
other
ternperature
general
th,e change in
tulttg,
but
temperature iF yery slieht,
F.
other
the ctrange per degree be-
word.s, ?n pniry]
",elue
room ternperature cleanges in viscosity
:
Thls temperature-viscop{ty,rel-atiSnshiP'
with
for
the
anlmal
which
glue,
grade and mixture
In
tr''igure
ate
shows a qertain
of !h"
solution
very
although
amount of variation
shown a nulrilcer of
.2
$rere presse<L wtrilg. ttre glue
as
solution.
$ested' j oints
on the Tqood.was at
-10-
2r.6
have
usually
approaches
rapiCly.
is
glues
Invqstigators
eff€gt",
of 8Oo to loo
In
eff ect
ttre glue,bef.ore
one d.egree. of
region
few minutes
_the.woQd.this
l-4Oo tr'. , the approximate
reconmended f or heatlng
viscosity
little
depends very
f gr t}1e f irst
Indded,
af+uer aninr,al glue has.b,een spread gn
rauch more important
and thie lapse
gluing
v+scosity
an animal- glge soluti-on'
upon temperature.
l-argely
amount of chanBe,de-
'
of time betr,veen spreadi.ng and pressing.
In
on
showing a mucle
some kinds
onse to thicken,
change than
rnore rapid
glue rnixed with
a vegetable
Af,ter
of water.
Ov a
an animal
general,
In
any one
the propor-
with
variation
show a considerable
of tkrese will
but
viscosity;
higb-.in
are normally
d'ifferent
lr
b
s
p
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s3J'nNtn
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A'lan3ssv
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+
(tt
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E
c o n s i s t e n ci e s,
the tem per atur e of the wood
o b ta i n e d b y var ying
a n d t l r e la p se o f ti me b e tween spr eading the glue and pr essing.
T r l e j o i n ts
ler
ma d e w e re o f yellow bir clr wlth a cer tified
pr opel-
glue about ee\rivalent to peter coopenrs standard No.l.
m i x t ' . ' . r e ch i l -re d i n to
the character
case'
a jelly
of failure
at 8gor .
o n l y o n e si d e o f e ach jolnt
sholus
The illustr ation
and the figures
strength
for
tbe
in each
r vas photogr aphed,, since the
other sidp would shorr ttre same cha:iacteristi.cs,
Each ten half
s p e e i m e n s a re *g ro u p e d to g ether in their
b1ock, and.
ihe blocks
are arranged. so as to shovr the more important
ing eonditions.
of 70oF.
12oo for
or iginal
Ihe g1ui,.ngwas done in ryfoom at a temperature
For harf
the speciuens the birch
2 0 n i n u te s b e fo re gluing,
r o o m t e r n p e ra tu re .
wood,was heated at
The other s wer e glued at
rn e a ch case pr essur es of, both 110 and 4oo
pounds per square inch for
t i n c e s r ,f i " € . ,
glu-
approximately
period.s of prelimlnary
IB hours and "assembly
contac't without pressure,
o f 3 , 5 , 8 , L 2 , 1 8 , a n d , 2 ) m i n u t e s r r / e r e u s e d . . T L r eg l u e w a s a t
approximately
o f t h e j oi n t
I40oE . r when spread on the .wood.,and both f aces
w e re co a te d -
ftr e ccated. sur faces wer e pr aced to-
gether as soon as spread, but pressure flras not applied
ur.rtil
t h e p r e d ete rmi n e a a sse mi l y time had..eJ.apsed,
T h e g Iu e , a s so on as it
t o c i i a n g e 1 n vi sco si ty,
w o o d a t 7 0 o r'. i t
was spr ead on the wood, bega n
a nd within
h a d ch i l l e d
into
fr om I to 2 minutes on the
a j elly.
- Ut' 215
on the heated. vr ood
it
changed much more. slow1y,
periods
was too fIui.d
it
The eff ect
ter. cf
t h e jo.int
ip
and for. the
shorter
on the birch-
t9 l8ive gqad ioints,
of , all
on the charac-
,these conditlons
qu:L.te clearly
assernbly
phown in' the
figure.
On
tlre ,,jo,l'4t strength was
n-3essures,,
'l
r r r,/
r r : f .ua
ha
n
',
r .rr
q.li
eI:lV prp ss ed, j oints but showed a reas cnably
.r n ' n t'r,c
t.Le kLeateclwooC-,,.1rit,h bgth
i n e re a se ,i ,4 ,st4 e n g th with assenbly tim es up to 18
c onsr s t e n t
n : i, n n t e s , , T h g q u i .ckl y, p 5 g ssg d j oints of the:heated wood ar e
t rrn i o . r r ' r. e J - a r-ve d .!r
j o l n ts.
i \t,both"the l- 8 and t]y,;e25 minute.
v
e + +
v ! q
J
v * r ! e P .
a s s . e m b l y ,l i f n g p th e j g i n ts.: w e re 6f,r good str ength' and
srderable .pe.rcen,t"gq,.o{, w,ggd,fa'ir.ure oeeu.rred:
a con-
Th,e jotnts
of i h e h e a t e d w o o d *g l u e d u n d e r. 1lO,,ppur - r ds
pr essur e tested
un:f ormly stronger ,!han. tho,Fe gl.up.dund.er 400 pounds.
,
0,n the other trand,. when the wood was not:heated
there was no indication
o f . F t a f v e d .j o i n t s , ' : a n d
prgssu,re prod,uced..unilf Arn]y str.ongef joints
p o u n d s p r e s s ure .
caused by partial
j oi- n t ;
a s s h o w n . b S r , t h eu l n i m u u r s t r e n g t h v e i t r u e s ;
or.ineomplete,cor-rtact.bver: portion3
of the
, T h e 4 0 0 p o u n d s p re sd u re, ,howev€r ;r ' ,pr dduceda complete
c c n t a c t a n d . j o i n ts
o f , u n i fp rrfl y
hi,gh' stfength,
Tkrese and many other t€sts
lesults
v is c o s i t y
have sfrown that
a i e o b t a i n e d . , w i t h g l r l e s ' ! ' i l r e nt h e y . a r 6 o f , t l l e
the best
proper
a t th e tl me o f .p fe ss ingl' "" Anir iial: gtr ues:$r henmixed
:12216
than ,the 150
U n d .e r th e ,'1 i gh.ter pr essufe thdr e wer e vr eak
the joints,
spots.in
15s',400pouhds
a n d . p r e p a re d fo r u se a re or dlnar tr y
d i a t e pre ssu re a fte r
thicken
sp reading.
for
imm e-
They should be allowed to
consid.erably on the wood or slloul4 be m:ixed thicker
originally.
Animal glue is at the best viscosity
rng ,L
by touch.
sticly
m uch too thin
If
it
is too thlck
to fo l l o vr th e fi n g er
d o w n i n to
d i sti n e t
for pressi
, which may be judged.
to rfstringft but sufficiently
a shor t dlstance and. then dr aw
sca r*s haped. ir r pr essions,
safest consistencli f or pressing.
is usec, good joints
it
Of course, if
*
is at the
proper care
may be madeby pressing before or after
t h e g l ue h a s re a cb e d th i s
condltion,
but the chances of se-
c u r i n g j o i n ts
o f ma xi n s:n str ength ar e not so favor able.
'Making
an extra thlck mixture or ilcookingfr the
g l u e u n ti l
it
h a s th i cke n ed consider ably fr om evapor ation nr ay
m a k e a fu rth e r
vi sco si ty
change unnecessar y, hut these pr ac-
tices are not economical of glue.
&cessive
i n g n o f th e g l u e a l so e n danger s its
c a s e i n g l u e s a re r o rd i n a rily,
heating or "cook-
str ength.
r nuch higher
vegetable and
in viscosity
than
a n i m a l a n d b ro o d g Iu e s, and do not need to und,er go so lar ge
a change before pressing;
c o m m o nl y o ccu r w i th
b e s t p r a cti ce
pressures if
ilstarved" joints
in fact,
th e se gIuds.
But,
eyen with them, it
to a vsi d . the inmediate application
the strongest posslble joints
especially with porous woods.
-13 -
d.onot
of high
are sought
is
The. rate at which any gl-ue changes on the wcqd depe n d s u p o n a n u mb e r o f co n d i tions,
sueh as the temper atur e
an d m o i s t u re co n te n t o f th e wood, the extent to which the
5 1 u e - . c o a i e ds u r f a c e s a r e e x p o s e C , t h e p r e s e n c e o r a b s e n c e o f
ai:: lri::re:.rts, and the qr.raniity of glue spread.
eoated.Iamrnations or plies
Are laid
\Meere the
together as soon as
s.freacl, the glue changes much more slow1y than rrhere left
e : r p o s e d t o th e a i r.
u n d " e r" c losed. assem bly an aver age spr ead.
of glue may remain in good. cond.iti,on for
from 15 to 20 nrin-
ute s ,
cur r ents,
o x e ve n J-o n g e r.
ma y d r y w i th i n
If
e xposed.to air
a fe vu mi n u te s until
past the r ight
a p o i n t w h e re p ro p e r a d h e si o n. ip impossible.
he a t e d , t h e d ryi n g p ro ce e d .s much faster
then occur within
or less for'a11
s e t v e r y q u i ckl y
poor ioints.
{very
short
the glue
stage, to
tyith the wood
and dr y spots m ay
time. vfhile this
glues, casein glues in particular
true more
dry and
o n h o t w o o d, and ther e is mush d.anger of
Heating the wood before gluihg is.Iiable,
theref ore,'to.cause 'tstarvedr joints"with animal glue and
'rdriedtt joints
( . g e eF i e , I )
vrith all glues.
A small quantity
ra p i d l y
t h an a l a rg e r
of glue naturally
a mo u n t.
tr ' or this
changes more
r eason a scanty
spread of animal glue vrhen applied. to heated, or warm wood
ha s b e e n f ou n d l e ss 1 j .a b 1 e to give r r star vedil joints
-l-4'.
2t6
than a
o
heavy spread, if
pressed quiekly;
the quantity
of glue spread.
h a s - ' l - e ssto .d o 'w i th p ';o duei- ng a r tstar vedr r ,i oint
than tha con a
sis'Lency cf the glue vr.l"ren
the pressure is appried..
p ) . e, ' a
tr'cr exam-
s'ta rve cl .j c;n f n a y be pr ccueed. r ,vith a spr ead of glue
trrut-l.e tl:a,'l useci to ob'i;a:r.na joint
v i d e d th .e g l u e i n th e fi rst
pro-
cf maxi;-.:rnsirengrla,
case is pr .essed.whil,e thin
and in
the second is allowed to ccme to the prcper ccndit,ion before
p r e s s i ng .
N o te , h cw e ve r, that
since a sma- r 1euantity
drj.es more qulckly: t}:an a larger
nore liable
to g i ve p o o r joints
aro.cunt, the thin
v,iher econditions
s1' glue
spread is
ar e cond.u.c i v e
t o r a p i d d .ryi n g o r l o n g exposur e befor e pr esstng,
&.t Aiuf_tf._prg
Pressing
SSJI3*! o._.I_o
r rlt Ske*elh
is an impor.r,e;ft lrait
cf' the gtru:ng opeya-
tion.
P re i ssu re i .s a p p l red in or d.er to
"br r ng tr gether ilr e sur f a c e s to b e j o i n e d a n d to hold then fir n- r - y' togeiher u,t:ir e il.re
g l u e s ets,
w i th o u t
B re ss ur e the gl.' .r e*,coei;ed' ir iu"esnig!r f; wa;p
' Pr essur e
m o r e o r l e ss fro m th e e ffeets of' the ad.Ced.
nr ,- r i' stur u.
forces
th e a i r
fro m th e gr ue l.ine and. also pr r :bab]- y ai.ds the
glue in penetrating
obtain
the ceils
of tjre v;coti, thus enabl,ing it
q.6ocd tror d..
fh e e xa ct a mo u.nt,of pr essur e to use is
p o r t a n ce th a n i s g e n e ra l ly
of less
in-
belier r ed,, ar :d the necessi,;y of a,p-
pl)-ing a fixed. amount is frequentl-y
-r5CIO
io
overemphasi.zed. For
e x a n p l . e , p re ssu re e ve n a s h l gh as 1,1000 pounds per ss- uar s
ir : c n r n a y p rcC u ce j ci n .'l ;s o f v er lr high str engthn wtr er eas r esults
equal-l-y gooC nay be obtained. hy merely n.rbbing the
s u r f a c e s t og e ti re :,
p ro vi d -e d the glue coati.ngs ar e of the
proper consistene:,; :er-r,J.
the rvood.surfaces are lt'ell machined
a n d . p r e p a r ed .
U ri d e r ce rta i n
conditions
other wise ldentical
presFures anSruvherqfron50 tto 5OO or more pound.s may give
satisfactory
la r g e l y
results.
In fact,
the effects
of pressure are
d e p e n d e n t u p o n th e consisteney of the g1ue.
which is thin
and.liquid
A,' g]- ue
a t the time oSbr esslng should he
g i v e n a c CIn p a ra ti ve l y Ii g h t
pr essur e, wher eas a th.ick one
sh o u l - d .r e e e i ve a h e a vy p re ssur e.
T h e e ffe ct
: a t , , h . r c ka nd a th i n
shown the results
o f p re ssur e on ioint
g l u e i s ilhistr ated
str engttr vr ith both
in Fig.
of tests madewith five
3"
Cifferent
Her e ar e
pres-
E i u r e s , 2 5 , ,O, :..5 O,4 OO, a n d. 600 pounds per sq.u.ar einch, and
'under
two d.ifferent temperature conctitions, !0o and 90oF.
Ih e j o i n t s
ma d ,ew e re i ,o f b i rch with
a b o u t e q u iva l e n t
solution
cer tified.
to P e te r Cooper ts Star r C- ar dI' Tc,.I. The Blue
was heated. to l4OoI'. wtren applied"
th e 7 O o c o n d i ti o n s
it
q u i ckl y
vrri.th.inf rom I
to 2 minrltes,
ed" inilc afirrr
jeli-y.
chilled.
lI
f)
\X,lhen
rrsed under
on tkr e wcod. usualiy
and at three min'ii.;es :,t had f orm-
0n the woo,l. at 9Oo it
-16L -/-t)
p::opeLler glue
char.rgedsLov'rly in
c
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s
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E
e c n s i s t e n cy a rl d . d i d - n o t for q into
c n d o f 2 5 mi n rb s,.
t
I
I
a fir m
Jer ly
even at, the
T h e qur faces, both coated vr ith glue, wer e
p r a c e d - to g e th e r a s so o n as spr eb,d,
and. wer e left for per iod.s
o f 3 , 1 2 " o r 2 ! ml n u b e s bef or e pr essur e
was appl.ied,.. The
r e s u l i s o f th e J, !p , a nd zj- minute per iod.s
wer e &ver aged.
'
together..
with
lihe room and wood"at gootr'.' the rfo-pound. pres_
.sure gave the raost d.epend.abreresults.
The ai, Fo, and J-!0pound pressures all gave about
the same average qtrength var_
ues, but with the. two l.ower preesure.s
the.;oints were weaker:
i n s p o ts. A d e e i d e d d ro pping off,
in- ,str ength occur r ed. vffr en
t h e p r e ssu re w a s. i n cre a sed to 400
ana 600 pounds per squar e
inch
T h e p re ssu re -strength
r elationship
was d.iff er ent,
however; when the room and wood were
at /gotr,. Under these.
conditions the glue jellied. bef
ore preqsure lqas applied.,.and
a n i n c r ea se l n th e p re ssu r e up
to 400 pounds per squar e inch
made a d'ecid'ed,improvement in j
oint strength and was espec i a l l y effi ca ci o u s i n o ver com lng.weak
spots. Both 400 and.
5 O Op o u n d .sp re ssu re p e r s qqar e
ingh gave vety str ong jointsn
as strong as the best of those glued.
in the warmer roor[. The
p l a c i n g o f th e p i e e e s to g ethdr
without. pr essur e as soon as
coated and vrhiLe the glue was stiil.
liguid
resulted. in adlre_
s i o n o v er a p a rt o f th e j oint;
then after the g.r ue had jellied
-t7 zt6
:
:
the r emaining
(. . r a p i d . p r 6 ce ss a t th e l o w e r tem per atur e) ,
use of
i: o r t i o n s w ere b ro u g h t i n to fu1I contaci only by the
're r y h i g h p re ssu re s.
T h i s a ccounts f Or the low anC higlr
'n i n i n m
s t r e ri ." i l l T a l .i l e s f o r the iight and heavy pr essur es'
^
-
{
I
i
I
re s p e c + , i v e l y, i r:. 'th e 7 ()o ro om .
gfuin g ConO:.-,ticns f ntelq@-en!.
T h e g l u i n g p ro ce ss,
ther ef or e, i' nvolqes a compfex
of which the amount of g3-u-ingpressure,
of f actors
perature
of gLue spread., are all
one factor
stiil
ma y b e va ri e d
r e s ul t,
laminations'
interdependent
p ro vi d .e d . th e rest ar e contr olLed
o f fa vo ra b l e
u n i l e r ce rta i n
Any
to compensate'
eom bina-
and. DoubLe ,$Preading
co nd.itions the r esul- ' fs obtained' wi} I
or double spread-ing is
is, whether one or both sid,es of the joint
glue"
r l j . : i i - ' e t r e r i ce
i n re su l ts,
T b is factor
will
m ake no appr eciable
p ro vided the glue is at the pr oper
c o n s i s t e n cy w l re n th e p re ssur e 1s applied' -
-182i.6
parbe.
one of r nany possible
depend. somewhat upon whettrer single
F , r . e I c o a t e d . w i th
and tlre
co n d i ti o n s.
Single
practiced.; that
of
o ver a lvide r ange and str ong ioin' ts
S u c c e s s d .e p e n d su p o n g e tti n g
tions
the tem-
of room and wood, the kind., grad.e and rnixture
g1ue, the manner and time of asserbting
quantity
I
If , however ' the
l
I
I
g L u e actu a l l y
jellles
b efor e pr essing,
j c r : - n t r mrrst b e co a te d fo r
p l : e s i u re s a re u se d .
the best r esults,
wili
in excessively
r apid dr ying,
o f g l ue d.istr ibuted. over the two sides
dtn,.
dry rircffiluickly
than if
and, is moxe l-iable
spread on but one sid.e.
r a n g e o f co n d i ti o n e ,
t h a t a g i ve n se t o f g tu i ng conditions
on aJ.1 kinds
pro p e rti e s.
over a wide
th e double spr ead.ing is m or e r ellable
tr'rom what has been said. it
$ame results
to cause vueak joints
But as a rule,
a n d w 11 1 g i ve th e h i .g h e r aver age joint
their
even though high
rf , or r the other hand, thb cond,ltions
s - r r ' : c u n d l n g th e g l u i 'i i g result
t h e s a,meq g a n ti tf
botb sld.es of, the
of woods.
so me ar e r ight
str ength.
must not be concluded
will
always produce the
Wood.svary greatly
in
and por ous, otir er s heavy
and dense; some are comparativeLy ufiiform in grain and.
texture, others are rnarked.ly nonunif orm in these respects.
some
a r e w e a k, o th e rs stro n g ; some shr ink or swer l excessiver y
w i t h m o l stu re ch a n g e s, other s var y but LittJ- e.
some contain
oils,
or g w n s; o th e rs a re compar atively fr ee of such sub_
stances.
some cut and surface evenly and. smoothJ.y; othe:is
a r e d i f fi € t& t
to ma ch i .n e at- all.
A1l these
vrrvev
vchar
r r a r q , l g acter
e g 4 . istics
{
I
a f f e c t rd o re \o r l e ss th e gluiRg pr oper ti.es of the
var ious
w o o d s an d th e se rvi e e th ey will give in gJ,ued constr uction.
_19-
under an e:ctr emely
$ o me vro o d s g l u e satisfactor lly
ay
v rs
* -e
l'a
r ol t i n g
J - ! . , r u n .r r :rn 6?n pt 6 .a L
trra I f -s
nrr
a no
ap
l ' l e l l e ro n
h
a L f c ii z rey o p
,.'1 nnlrc
diffcrentl"y.
jci.-':.i;s,
nach ccnsists
of five
'Ihe urlper par''c of the
after
part
the appea:'ance
had been cut up and tested;
(trorizcntal
;ugether by j oints
(vertical
ror'/s ) and blog]<s
Tlie tinie
colurnns ) .
i ; r v e e n s p r e a d . i n g t h e g l u e a , n d .p r e s s i n g
ntntltes
f or the
A.icrr.g the lower
l-eft
margin
of the diagram
,trr-rnerals designated
rrassernbly timerr.
.lressu.re conditicns
for
.:ach co].umn.
on bieck
.iel.iy af, al-l jcints
. ' ' r l t e np r e s s e c l ,
each block
Na.4
\{Lren removed from
variation
.ous joints,
in
although
:rad been applied
*rere
in
'it6
tire
the liead of
visccsities
th.e press,
each case.
It
the bloeks
pressed
the
is
the wood had been heated. befcre
Ailarger
and
a firm
d.epend.ing
and. assem.biy times.
apprnxirnate)_y
rore gltte squeezed ou't.
are
these
0n the' other blocksl
amount of glue
the
each block.
cf
the glue had chil-Lec into
cond.itions
be-
and IJ
7, 1I,
are noted at
glue was of various
the
. .
elapsing
The temi:,erature
bef ore pressing.
'rpon the temperature
3reat
y . r a s3 ,
nurnbered joi-nts
consecutlvely
and. four
shol.ls the blocks
illustration
the blocks
glued
alll
bl ocks,
laminations
'i;h.e lower
L'hen l:emoved f ri'rn r.:l:e plt:ss,
of the joints
oak
In Fj.g- 4 ar e shown fout wliite
r q - i c l er a n g e o f ccn d i tj .o n s,
showed. a
frorn the
var-
same ,a:nount of glue
se.Lj-e.rident
that.
gluing
was much
quantity
tnere
of
glue was also
c
BLOCK
BLOCK
4
BLOCK
3
o',,o't
9Jr8?,5'
*-ET!l'
LB9. PRES9UR€
r50LBs
I5O
2
I
BLOC K
ROOF4 AT 9O"F
wooD HEA'IED lo FllNlT l4o-F
t5O LBl PRESsIJR€
2
RoOM AT 9OOE
2 HRAI9O"F
wooo HELo
-
IUMT STFT'ICTH
HtNAve
2353
?096
,l
I
F
lfooo
FAILI'PE
917c
SP ;uillr 3
6R lHrN.
.1t l?4oz
VrrQOo
H
E.
?
FAILURE
o6cle
sP. lUNlr
$tooo
?{i; '^iir': ?$l'iii
sP.r u N r T! rrrpix
c R .I H t l .
.re|
zoe
sP I
wooo
FAILURE 6R I
to I
6o0/o
AVE
?360
I
.!
c
z ' 7
- z
liJNlT
I HIN
s
T
wooo
AVg,
tulo4
FAI!URE
51 o/o
l'655
GR I HIJT
.76
AW
21t6
FAILU€E
6696
;; l-d,:i.
.16
l?t6e
FAILIJiE
92Ao
lt7ez
OR
17
F
fl
f - .
- 6
0
o
I UNIT
I mrw
irac5
AVE
2251
sP. , uNlT i
vpoo
AVE.
FAILURE
GR I M I N
e 2 % . 7 6 ?roo ?490
|
9P . UNIT STRCnGTll tlr@O
$rooD
FAILU"T
AvE.
FAILURE G R . I H l N .
8.Oo/o
75 12255
?5o4
84o/o
sP I unlT
G R . l M r N . Ave
16
1145 ?t55
|
SP I
wooD
FAILUR€ Og I
.77i
87'/o
-=
t
z
SP UNIT 3.'QEN6TX
ur.ilT STREI{€TH ti/ooO
AVE
M IN
AVT
FAILURE 6 R M I N
2379
7A l82e
A6"/.
?O24
t4oo
WOOO
FAILURE
.13 "/o
5P.
GR
76
SP UNIT 9TREN6TH
U N I T :9 T R E N O T H WOOO
AVE
FAILURE CR MIX.
AVE
MIN
69/o
12 t8'a5 ?\4
?
t
9
a
?093
THE
.+ JOINTS GLUED U
- NDER DIFFERENT CONDITIONS,9HOM/ING
sPF-CIMENs
nND TEsreD
sl-ocx5
H(J336i^PriFF'c)
- (/'BouT^
GLUE
ANIMAL
wrTi
TEOUIVALENT
lt'/A
l'lllxED
tlol)
srrrrrrrARD
A/ooD
FA!LURE
'f
Ao/o
5P
G. tP7
GLUEO
ID
PETER
.presrsed out frorn the
, i , s s e t r , b l - e dl a s t .
sides
jointe,
top
0n block
f'l+ned- cver
whlc}. had been coated. a,rrd
Ne.4 the lines
the ec.ges when the
of d.riir shown on the
gr-ire lvas spreal,
but
a
c - le s + : n s p e r c t , i . o n n a y s h o w i n p l _ a e e s t h e j - j . n e s o f c o n g e a l e d o r
jc-l l-j eii gir;e w.;ri;,]: T'r3r'erf or.'ced. out b-rr the ]i-igir presslr.re.
iio'Lr,vi'ihsiani:-ng
whieh
the
variation
joint
f our blocks
in
ences as did
quality
test
throughout
exist'were
occurred. in
values
and per
The tendency
were much the
t h e v r o o d .i t s e r f
assemblies),
cent
is
in
occurs
in
gluing
lvhite
are more or less
i-ng central
true
filred
American
the .two spread Last.
somevrha'Ubelornr the
vrhat 'wourd have appeared. r,vith certain
here
shor,vn are
with
oak, q6pecies
tyroses.
spec-ies.
cther
quite
o,ver&g€;.
as compared to
typicalof
.vr,'hat
in v;hj.ch the pores
otir.er woocs, inciud-
mahogany and a number of conif ers
softlroods,
have al-sc been found to
give excellent,
throughcut
an extremery
of gruing
wide range
-2t 2l-6
in
p e r h . a p s s o f i r . ei n d i c a -
h{'tr'rever, especially
The results
the
in
os shov,rnby mirri,re:m strengt):
vrood. failures
slight,
euch d.iffer-
vras no one joint
, and there
lio.I
tlre
of the fail-rrre
There is
in block
saule*
to differences
A higih percentage
1ow throughout,
(3 and' T-minute
great.
cf pressing,
the tlme
due chiefty
of s'barved.jcints
Li ons und.er
c or.rcL-i-
gIued., and tire conseciuent
o f 6 , J - u ea t
of the rnood.
vrh"ich tested
tion
were
viscosity
strengths
the lvi.d.ely varian'b
joints
concitj+ns.
or
on ttre other hancl, has been f ound- to glve
Yellovr birctr,
s : t a i v e d . j oi -n ts
r r o ' i t h c e r t ai n
o f 1 o w stre n gth
und.er cond.itions identical
to the white
o f th o se a p p l y ing
oak shown j- n
to
Hard roa!,le, r€d oak, and ash appear to be similar
Tig.1-.
: , r e l - c- lw b i r ctr
In gener al,
i n g l u .i i rg ch a :r acter lstics.
( ' F e j l - - p c r o u sw o o o s o f h i g i r str ength pr cper ties
r r , i f : e j - c u l t to g l rre a n d re q u i r e
ar e the m ost,
the most pr ecise
a n d m e t h od s i n tl rd e r to o b tain satisfactor y
the
conditions
Studies
ioints.
i l r e n c w i n p ro g re ss u :t, th e Sor est Pr oducts Labor ator y as a
result.cf
woods nsw connr enl- y
i l fu i ch 1 t i s tro p e d. that all
g 1 u e d m a y b e g ro ri p e d a cco rdihg to thelr
glulng ehar acter is-
tics.
t r 'o r e xa n p l e , th e w o od.s in which star ved. joints
liable
t o o e e u r w o u l d b e g r ouped. in one class,
glue easily
ih.e like;
point
under a wid.e range of cond.itions
ar e
those which
and'
in anottrer,
b u t a s ye t th e studies have not pr ogr essed tc a
wkrere the lines
can be d.ravrnwith
exactness.
Gonclusi ons
fhe maj or part
paper were mad.e vrith
other
tests
vegetable
sions,
true,
of the
anlmal
tests
glueo but
while
witLrin
It
appl-ying
is believed.
especially
reasonablel.im:-ts,
that
for
tc
thelr
al-l-i
this
in
eompletion
casej.n and'
the f lllovri-ng
to animal
- 22-
2]-5
since
blood, albumin,
have been made with
g1ues.
referred'
glues,
concfu-
will
hold
1 . T h e mo st i mp o rta n t single f,actor in secur ing
good joints is the 1fi.scasity or'consistency of
the glue at the time prbssure is app11ed. Other
factors are of importance in so far as'they affe ct th e g l .u e vi scosity at that moment, but of
l i ttl e
n o me n t o ther r r lse.
2.
3.
4
If the glue is very viscous, such as a jellied
a r . i u a l : r g J - u e ,h i g h p r e s s u r e s ( + O O t o 6 O Op o u n d s
p e r scr.u a rei n ch ) ar e ad.visable in or der to secur e
good contact and high joint strength,
Under con:
d l t i o n s w h e r e t h e g J . u ej e l l t f l e s
bef ore pressing,
both sides of the joint should be coated vrith.
glue.
If th e g l u e i s ve r y thin and l1quid at the tim e
th e p re ssu re i s applied, star ved or weak join.bs
a re ve {y l i ke l " y to r esult.
The use of low pr essu re s (2 5 to 5 o pounds per sq,uar e inch) may give
successful results,undei these conditionsr-but
i s n o t to b e d e pended upon, as a slight war p nay
easlly prevent good contactfh e a mo u n t o f j o i ning fr essur e, the tem per atur e of
room and wood, the manner and. tlme. of assembling
lami.nations, the glue mi.xture and quantity of
g l u e sp re a d . re q uir ed to give good joints ar e all
i n te rd e p e n d e n t.
Any of these factor s nay be
varied over a vride range and. stiIl, permit strong
joints, provided the other factors are controlled
a e co r d i n g l y ,
5 . PFSs_ure.
S t r o n g j c i n t s c a n b e s e c u r e d .w i t h , j o l n rng pressures varying from 25 up to 500 pounds
ler square inch or even more,.. I,ow pressures are
i e q u i re d i f th e glue is ver y,Lieuid,
and higlr
p re ssu re s i f tl i e glue has chi} } ed, or par tiaj,l_y
d ,ri e d . Io w p re ssur es with chi1led. elue and high
BTessures with:very 1i,quid glue. give weak joints.
A
Tef.nperature. A Lotr remperature (around. Zoof')
ca u se s, h i g h g ra d e animal gfues.to chiII quickfy
u p o n th e w o o d a nd necessitates r elativelt
high
p re ssu re s f o r g ood j ointS.
.A temper atur b of 90otr .
ke e p s th q g l u e 1 iquia longer ; hence mediun pr es_
su i 'e s a n d a sse mbling tlm eJ ar e desir able.
ff the
v'ro o di s w a rme d for 20 minutes' or m or e at I1OOI,.
or higher the glue rernains liquid
stil_l longer;
-23 *
2;-6
and l'ow pres.sures and. long assembly period.s
f-ess .trouble is encountered
a.re desirable.
in uslng heated. wood in a 7Oo gl-ue room'than
I n g e n e r a 'l f a,v ohtesa t e d w o o d . ,
in a lOo room.
the produckeeping -uhe glue liquid,
j
ti on of star'.red olnts; i:Iteating als o increases
because it
the l-ikelj-hocd of weak ioints,
fasors vrarpi-ng of the wood. and" rapid' Cryi-ng of
to spread a
the Blue- ar:d makes it dlfficuit
g
l
u
e
quantity
on the wooct ln
suffic:-ent
of the
pIace.
the flrst
I
r1
R
-'-'
*
tleat is, the time vrhich elapses
IhS egpSmbiJj-lme,
the pres*
l-tetweeir spreading the glue and applying
o
nsistency
c
t
t
r
e
upon
sure has an important
effect
wooo. in
g1ue.
glue
heated
of the
With animal
and.
are
t
i
m
e
s
a warm roomf relatively
long assembly
a
i
n
d.esirable.
V{ith the sime h6ated wood
70?
room, shorter assenrloly periods may be saf e1y used'
With both wood and room at ?OoF., the glue chills
immed-i.ately; and wtren it is in this condition
good. results
can be obtained rvith either long or
r r O p e n a s s e m b J - y r,r t h a t i s '
short assenrlcly periods.
,
g
i
u
e
allowing
the spiead
to remain expcsed' to the
air,
induces rapid d.rying and is not desirable exvery
cept where the Lssembly iime is unlformly
o
f the
short"
Ord,inarily the desired. viscosity
glue may be seeured. more ad.vantageously througtr
an adjustment of other cond.itions than assembly
time and method.
spread.
A spread. of about Jf grams
A'r4p-gpt of elw
of glue mixture pcr square foot of j oint area can
be eiqpected to give satisfacbory
resu-lts under
most conditions.
With cond"ltions vrhich tend to
produce starved. joints
spread of glue
a light
g,i-.resstronger jo:-nts than i ]reavy spread; but l'';ittr conditions
under which the g.Lue tends to dry
Uncler conexcessively a heavy spread is trbtter.
ditions wtrere the glue c}iIls,
the anouvrt spread
is not very imFort,ant, so 1ong as tl- e vrood is
well covered..
may be made
9- 9-1-ge--Ui$!gleJoints
of higlr strengtlr
f;orn Fie
concentrations
solutions
of different
if the ottrer gluing conditions
con:
are prcperly
troll qd. A med.iummixture is to be preferred' if
-24 tt-lD
il r)
,
a vl i d e ra n g e o f pr e8eur e, tem per atur e,' and
assembly conditions is likeIy to be encountered.
10. QiedS-a,tq-do"1rr!rpg51"dlng. Spreading the
g ru e o n o n e o r both sides of the j oint glves
a b o u t th e sa rce r esults, pr ovided the glue
r e e i e t r e st h e ' p r o p e r c o n s i e t e n n y w h e n p r e s s e d . ,
ff , l e e vre re r, i t cnills io a 3effy, d- ouble
spreading is 1:reier.able; if the condltions
cau$e excessively rapid drying, single spreb,duantity of'efuel wifl be
l n g , w l t h t h e s a m e q- Uncler
th e mcre re l i a b 1e.
a wide r ange of con_
d i ti .o n s d o u b l e spr .ead.ing is m or e dependable.
1 1 . S p S cr_ ,e S . T h e re is a consid.er able d.iff er ence.
1 n th e g l u i n g pr oper ties of the differ ent
s p e c i e s . 0 p e n - p o r o u g w . o o d . sa r e m u c h m o r e s u b _
jeet to starved joints than are the 1ess por_
ous. On the other.hand., ro marked differ_
e n e e s e a n b e d e ' b e c t e d a n r o n gt h e s p e c i e s w h e n
glued under ccnditions wheie the glue is relati ve l y th i ck w hen pr essur e 1s applieaA.Lmost
any species can be easily and satisfactorily
gluied under intelligenily
controlled condi_
ti o n s .
-?-52L6