MODERN GLUE-ROOM EQUIPMENT
With the increased knowledge of the nature of glue, and of proper
methods of handling, has come a great improvement in apparatus used.
The primitive way of melting glue was to heat it in an open pot over
a fire. No heed was given to the loss through evaporation; nor to the
scalding of glue; nor to the dirty condition of the glue-pot, and
consequently contamination of fresh glue by the remains of former melts
frequently occurred.
We say “primitive” methods advisedly in speaking of this old-time way
of melting glue; for in the light of modern knowledge such methods
belong to a day gone by. Yet some glue-rooms still use the old open
glue-pot, and many others use apparatus which shows little, if any,
improvement.
Modern glue-room appliances are now available for every glue-room, for
every purpose. No glue user, large or small, can afford to use any but
modern, scientific equipment. The saving in time, and in materials, and
in improved quality of the completed work, and in the greater respect
and increased efficiency of workers in the glue-room, all these things
result in quickly repaying the increased outlay required.
ONLY COPPER, BRASS, ALUMINUM SHOULD COME INTO CONTACT WITH GLUE
The advantage of using copper, brass, and aluminum in glue-room
appliances, due to their self-cleansing properties, already has been
mentioned.
In apparatus designed for melting glue the use of copper, brass, and
aluminum is absolutely required for economy and good results. Copper,
brass, and aluminum are the only materials available that are not
affected unfavorably by the action of acids in glue, steam and water;
by boiler compounds, dirt, pipe-rust and sediment.
An iron agitator or stirrer in a glue-heater is corroded so quickly by
the acids in glue, water and steam that in six months it is unfit for
use.
A brass agitator, on the other hand, will last practically forever. So
it is with every part of the glue-heater with which glue comes into
direct contact.
The glue user who has had experience with galvanized iron heaters
does not need to be told that the iron quickly is eaten away and the
apparatus rendered unfit for use. It is certainly the part of wisdom to
invest in copper, brass, and aluminum equipment, to which metals there
is practically no “wear-out.”
Glue-room equipment of iron is still sold, but only because there are
still some users who are so blinded by the initial small saving in
outlay, as not to see the saving that accrues in the end from using
indestructible materials--and the additional saving due to good work
and economy of glue.
A SCIENTIFIC GLUE-HEATER
The facts already mentioned about the melting of glue should be borne
in mind in choosing a glue melter, or glue-heater--always remembering
in particular that it is of utmost importance that the heating agent
should not come into direct contact with glue, and that the glue should
not be overheated in preparation.
The glue-heater that has been proved most economical and efficient in
wide-spread use has an air-tight glue chamber (to prevent evaporation),
surrounded by a water-jacket (to prevent burning or scalding glue),
the water in the jacket being heated either by direct injection of
steam or by the use of copper heating coils. Electricity is also used
successfully as a heating agent.
The heater is made of copper and brass throughout, and is therefore not
affected by the harmful effect of acids in glue, steam and water, dirt,
grease, pipe-rust, sediment and other harmful substances. In this
heater glue is reduced to a uniform and correct working consistency,
and with unusual speed, if desired; 5 gallons of glue may be melted in
less than 15 minutes, and as much as 50 gallons in less than one hour.
It has already been noticed that excessive speed in heating requires a
degree of heat that is injurious.
A thermometer is provided with this heater that gives accurate readings
of the temperature within the glue chamber, so that the heat may be
turned off when the danger point of 150° F. is reached.
THE AUTOMATIC TEMPERATURE CONTROLLER
A still more recent and valuable improvement is the automatic
temperature controller, a thermostatic valve which operates
automatically to keep the temperature in the glue chamber between 145°
F. and 150° F., or at any temperature for which it is set.
Not only overheating of the glue is prevented, but expense of
supervision is reduced. The heater does not need to be constantly
watched for fear glue will not be kept at correct temperature.
This particular heater is also provided with a brass agitator (hand
or power) for keeping glue thoroughly mixed while melting, and with a
special faucet by means of which the melted glue is drawn off without
dripping or clogging. It is made in sizes from 2 gallons to 500 gallons
liquid capacity, and for use with any heating agent--gas, electricity,
or steam.
An apparatus of this kind not only facilitates economical melting of
glue, by preventing evaporation, waste, formation of scum, sour and
dirty glue, but it also insures uniform “spread.” Furthermore, it is
a great incentive to accuracy and cleanliness on the part of workmen,
encouraging them to good work by providing them with a neat and clean
glue-melting appliance, in contrast with the old-fashioned, unsightly
and ill-smelling “glue-pot;” and providing them also with glue that has
been properly prepared.
KEEP STEAM AWAY FROM GLUE
Above all, keep steam away from glue. Some glue-melting devices are
on the market in which glue is prepared by subjecting to the direct
application of steam. This produces only bad results. All authorities
are now agreed on this subject. It is safe to say that the chief
development in glue-room methods of the past ten years hinges entirely
on the discovery of these facts: that steam ruins glue; that glue
never should be heated above 130° to 150° F. at the utmost; that the
other properties in steam--boiler compounds, acids, dirt, pipe-rust,
sediment, and grease--are absolutely injurious to glue.
Do not let the argument of speed blind you to the damage resulting
from the live steam type of dissolver. If you want speed, use a type
of instantaneous dissolver that prevents steam from coming directly
into contact with glue. The very best practice, the one generally
recommended by experts, is to heat glue slowly, with a heat not above
130° to 150° F. Then the glue is in the very best possible condition
for work.
The effect of acids is such that they have been known to turn a pot of
good glue black.
GLUE SPREADERS
In wood-working establishments where much glue is used, it should be
applied mechanically, by means of glue spreaders.
Some spreaders are made with Brussels carpet covering for rolls, but
this is not good practice. The carpet covering absorbs dirt quickly,
is difficult to keep clean, is liable to tear, is sure to stretch and
eventually rots and wears out.
The simplest, cleanest, and cheapest method in the long run is to have
rolls with corrugated surface; even spread is thus assured, and there
is practically no “wear-out” to them.
In order to keep glue at right temperature during use, it is best to
have the glue-pans surrounded by heating coils. These may easily be
connected with the steam boiler or gas heater; or electricity may be
used.
A further improvement is to have the spreader connected with the
glue-heater, as then only a minimum quantity of glue need be carried in
the pans. By this method a quantity of glue sufficient for a day’s work
or half-day’s work may be melted in the morning and maintained steadily
at uniform thickness and temperature until used. The melted glue is fed
to the pans only as needed, through open copper troughs.
Glue pans should of course be made of copper, for the reasons already
mentioned. Another advantage is that copper pans are self-cleaning, as
glue does not adhere to this material.
Spreaders may be had as a single-roll machine, for coating one side of
stock, or as a double-roll, for coating both sides, or as a combination
single and double-roll. They may be operated by hand or with power.
When used with power a good operator can coat 13,500 lineal feet per
day, with a good machine. The results with a glue spreader are largely
due to the proper adjustment of the scrapers.
Glue spreaders can be used to coat flats, edges, straights and mitres
equally well.
For coating plain and straight surfaces, use a solid roll. For tongued
and grooved pieces, V-shaped stock, dovetails and other irregular
shapes, use a brush roll. Some spreaders are fitted with combination
solid and brush roll; a very convenient and economical arrangement.
The spreaders should be kept scrupulously clean, and also the brushes,
if any are used. Clean brushes by filling glue pan with hot water and
revolving the brush in it until all the glue has been removed.
CLAMPS AND PRESSES
After gluing, the work should be kept under pressure for a sufficient
length of time to insure perfect adhesion. In the case of hide glues
the time required is from three to four hours. The time varies with
variations in the glue, in condition of stock, and in temperature of
room. No general statement can be made to cover the case; experience is
the best guide. Either retaining clamps or presses are used.
Pressure should be distributed as evenly as possible. Presses may be
had in almost every style for every need--open on one side, or on two
sides; for veneered stock; sectional presses; etc. Very excellent
presses are being made of structural steel. They are practically
indestructible, very efficient, and yet simple in operation.
In selecting a veneer press equipment the amount of pressure per
square inch must first be determined. Opinion varies with different
manufacturers, some using 100 pounds, some 200 pounds, per square
inch. The best general results are obtained by using 150 pounds per
square inch. All presses made with a 2-inch screw should be designed to
withstand a pressure of 8 tons or 16,000 pounds per screw. To find the
tonnage of press that you require, multiply the length by the width of
stock, this by the pressure per inch you desire and divide the results
by 2,000. This will equal the tons pressure required. The number of
screws per press can then be determined.
DISTRIBUTING GLUE IN LARGE PLANTS
Glue is used in the wood-working industry mainly for making joints and
veneers.
In large establishments, where many workmen are employed, a good plan
for distributing the melted glue is to arrange a battery of small
glue-pots, or warmers, strung along a pipe line running from the steam
boiler or gas heater.
Individual pots of copper which are filled at the central source of
supply fit into cast-iron jackets, kept warm by steam which comes from
the pipe line. The requisite temperature is thus maintained at minimum
cost.
The valves may be so arranged as to cut off any warmer not in use,
avoiding waste of heat. The arrangement is very satisfactory even in
comparatively small establishments, and may be adapted to any number of
individual pots.
ADVANTAGES OF ELECTRICAL EQUIPMENT
When steam is used as the heating agent, only about one-fifth the
amount of heat generated is actually used for heating the glue.
Four-fifths of it radiates through the pipes and creates a heat so
intense that the efficiency of the workmen is reduced fully one-half
in summer. With gas as the heating agent, the same conditions are
present as with steam, plus the fire risk, which in itself is so great
as to make gas extremely inadvisable.
Electricity is coming into greater favor every year, with the
improvement of electrical glue-heating appliances. Electricity is still
too expensive to justify its use as a heating agent, except for the
exact purpose desired, but modern electrical devices, including the
jacketed, heat-retaining glue-pot, make it possible to use electricity
without waste.
The cost is less than either steam or gas and its advantages are so
great that thousands of institutions are now using these “fireless”
glue-heaters. The best electric glue-heaters are made of copper and
brass, the greatest conductors of heat. They require much less heat
than any other pot and the heat is required for just about one-fifth
the time, owing to the heat-retaining jacket.