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THE
MAY 30, 1925
MUSIC TRADE
151
REVIEW
Composition and Varieties of Glues
The Forest Products Laboratory, Maintained by the Federal Government at Madison, Wis., Gives the
Results of Extensive Experiments Which Have Been Carried on Over a Long Period by This
Organization, and Analyzes Five Principal Types of This Commodity
IANO superintendents, like most wood-
working executives, are divided as to a pref-
erence for the various glues in general use.
Some superintendents have prepared figures
from their experimentation with glues, showing
a distinct superiority for vegetable glues. Others
P
in price from 12 to 24 cents, different grades of
arrimal glue from 12 to 30 cents, and dried
blood-albumin, suitable for making glue, from
16 to 38 cents per pound.
"Animal glue, frequently referred to as 'hot
glue,' has been in use a long time and is famil-
COMPARISON OF VARIOUS GLUES
Point of comparison
Source of principal
ingredient
Spread*
Extremes reported
Common range
Mixing
Application
Temperature of
press
Animal glue
Casein glue
Vegetable glue
Animal hides, bones, Casein from milk Starch, generally
etc.
cassava
Blood glue
Liquid glue
Soluble dried blood Animal glue, or skins,
bones, etc., of fish
20 to 50
25 to 35
Soaked in water
then melted
30 to 100
No data
Mixed cold
Requires no prepara-
tion
Applied cold by hand
or with mechanic.il
spreader
Hot or cold, depend-
ing on formula used
Applied cold or
warm, usually by
hand
Cold
30 to 80
35 to 55
Mixed cold
35 to 70
35 to 55
Mjxed with alkali
and water, with or
without heat; can be
made without alkali
Applied warm with Applied cold with Applied cold with
brush or mechanical brush or mechan mechanical spreader
spreader
ical spreader
Cold; hot cauls
Cold
Cold
frequently used
Strength (block shear High grade; have Similar to medium
greater shear
test)
grade animal glue
strength than strong-
est American woods;
medium grades
slightly lower
Naturally low, but High or low, as
Water resistance
can be increased by required
chemical treatment
Staining
Does not stain
Stains wood of
some species
Uses in woodworking High grade, where a
strong joint is de-
sired ; low grade
sometimes used for
veneering, especially
where it is desired to
prevent staining
Similar to medium
gr a
Similar to .or slightly Good
similar
XJUUU grades
gl«UC9
DII11I14I
less than medium
to medium grade ani-
grade animal glue
mal glue; some
brands very weak
Low
High
If mixed with caustic Does not stain, but
soda, stains wood of the glue is very dark
some species
and may show
through thin veneer
T o some extent for Almost entirely ' for
Mainly where
water resistance joint work, but main- water-resistant ply-
ly in veneered work wood for aircraft or
is desired in
veneered or joint where good strength automobiles and for
at low cost is desired articles to be molded
work
after boiling water
Low
Does not stain
Mainly for repair
work and gluing
mall articles by
hand
*Expressed in square feet of single glue line per pound of dry glue for veneer work.
The Composition of Different Types of Glue
have found casein glues more satisfactory for
their purposes.
Extensive experiments with glues have been
made for years by the Forest Products Labor-
atory, Madison, Wis., and a treatise, dealing
comparatively with the five principal types of
glues, has been printed by this institution re-
cently. In this article, glues adapted for glu-
ing wood are conveniently divided into five
classes, as follows:
"1. Animal glues. These are made from the
hides, hoofs, horns, bones and fleshings of ani-
mals, mostly cattle. They come in dry form
and must be mixed with water and melted.
"2. Casein glues. They are composed of
casein, lime and certain other chemical ingredi-
ents. These glues are commonly sold in pre-
pared form, requiring only the addition of
water, but may be mixed by the addition of the
separate materials to the water.
"3. Vegetable glues. These are made from
starch, usually cassava starch, and sold in pow-
dered form. They may be mixed cold with
water and alkali, but heat is commonly used in
their preparation.
"4. Blood-albumin glues. These glues are
made from soluble blood albumin, a product
recovered from the blood of animals. They
must be mixed from the separate ingredients
just before use, since they deteriorate rapidly
on standing.
"5. Liquid glues. They are commonly made
from the heads, skins, bones and swimming
bladders of fish. Some liquid glues are made
from animal glues and other materials. They
come in prepared form ready for immediate use,
"Vegetable glues are the cheapest glues, nor-
mally ranging in price from about 7 to 11 cents
per pound. Prepared casein glues may range
iar to all woodworkers. The principal desira-
ble properties of animal glue are its great
strength and reliability in the higher grades, its
free-flowing consistency, and the fact that it
does not stain wood. So far no glue has been
found by the woodworking industry to be as
suitable as animal glue for hand spreading on
irregularly shaped joints, although a cheaper
glue would be very desirable. The price of
animal glue is the chief factor which limits its
use. The fact that it is not highly water-
resistant is occasionally a drawback.
Casein Glue
"Casein glue has been used commercially for
a much shorter time than animal glue, and its
possibilities and limitations are not so well
known. It has sufficient strength for either
veneer or joint work. It is used cold, and when
properly mixed it can be spread with a brush.
The property most featured is its high water-
resistance, which makes it suitable for gluing
articles to be used under moist conditions. Not
all casein glues are water-resistant, however;
there are some on the market which are made
to compete with vegetable glue and for which
no great water-resistance is claimed. Among
the disadvantages of caein glues arc their ten-
dency to stain thin veneer and the relatively
short working life of some kinds. It is claimed
that this trouble has been overcome to a cer-
tain extent in some glues. They arc somewhat
harder on tools than animal and vegetable glues.
Possibly this objection can be overcome by
altering formulas or by using different steel in
the tools.
Vegetable Glue
"Vegetable glues have found wide use in re-
cent years because they are cheap, can be used
cold, and remain in good working condition free
from decomposition for many days. They arc
extremely viscous, and it is not practicable to
spread them by hand. Their lack of water re-
sistance and the fact that they usually cause
staining in thin, fancy veneer are factors lim-
iting their use. They set relatively slowly and
for this reason are not so well adapted for
joint work. Vegetable glues have been studied
and developed almost entirely by private initia-
tive, and there has been much litigation over
patent rights during the past few years.
Blood Albumin
"Blood-albumin glue has shown notably high
resistance to moisture, especially in the boiling
test. This makes it particularly suitable for
gluing plywood which is later to be softened
in hot water and molded. The production of
molded plywood articles has been very limited,
but it offers a good field for future develop-
ment. In the past the chief drawback to the
use of blood glues has been the necessity for
hot-pressing, but recent tests have shown that
a highly water-resistant blood glue may be de-
veloped which can be cold-pressed successfully.
Liquid Glues
"Liquid glues are, in general, similar in prop-
erties to animal glue. Some brands are quite
equal in strength to good joint glues, but other
brands are very weak and unreliable. Their
great advantage is that they come in prepared
form, ready for immediate use. This makes
them particularly suitable for patch work and
small gluing jobs. The factors which limit
their use are their high price, their lack of
water-resistance, and the difficulty in distin-
guishing between good and poor brands.
Veneer Glues
"Generally speaking, present vegetable and
blood-albumin glues are veneer glues, while
animal and casein glues are used both as veneer
and as joint glues. As between animal and
casein glue for joint work, if freedom from
staining is important animal glue is preferable;
if water-resistance is of importance then a
casein glue should be selected. Because of the
necessity of heat in the preparation and use of
animal glue, the casein cold glue will probably
be favored if both glues are otherwise equally
well adapted."
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