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.