GENERAL PROPERTIES OF HIDE GLUE
In physical form, hide glues are odorless, dry, hard materials ranging in color from amber to dark brown. Generally they are supplied in ground form but occasionally pearl and flake forms are available. Form and color have no relationship to grading or quality. Ground forms are easiest to use as they more readily absorb water. They are stable in ambient storage conditions under which they have an unlimited shelf life.
PREPARATION OF HIDE GLUE FOR USE
The preparation of hide glue is exceedingly simple. The proper amounts of dry glue and cold water are mixed together and the glue allowed to soak until swollen. The swollen glue is then melted at 140o F (mild heat) and stirred until dissolved. The glue solution is then ready for immediate use.
While hide glue will stand considerable abuse in its preparation and use, there are a few basic considerations which will enable the user to always obtain maximum economy and uniformity of working properties in the handling of this material.
- Use Clean Equipment
Clean equipment means a clean glue solution with best results.
2. Weigh Glue and Water
Correct glue-water ratios insure uniform, consistent working properties of the glue solution. While it is best to weigh the glue and water, adequate control can be obtained with careful volume measurement (refer to Dry Mix and Ratio/Density page 15).
- Soak in Clean, Cold Water
For general adhesive work the dry glue should always be soaked in clean, cold tap water to insure speedy glue preparation. Typical ground glue will require 30-45 minutes to soak. Coarser ground glues will require 1 to 2 hours to thoroughly swell; flake glues, from 2 to 8 hours, depending on thickness of the flake.
- Pour Dry Glue into Water
To minimize possible lumping and to insure speedy glue preparation, the dry glue is preferably added slowly to the cold water with constant stirring until the dry glue is wet-out. Then let stand to allow the ground glue to become swollen.
- Use Gentle Heat
When glue has been thoroughly soaked until soft, it is then preferably heated in a jacketed tank or pot. Swollen glue dissolves readily at temperatures from 110o to 150o F with gentle stirring. A glue temperature in excess of 140o to 150o F is unnecessary as it, increases evaporation losses, slows the speed of set, and introduces needless process variables.
- Preparation Equipment
A jacketed mixing kettle permits optimum preparation of glue solutions. This kettle may be large or small, depending on specific needs. For very small batches a “double boiler” is satisfactory or the use of a water-jacketed glue pot. The “jacketed” feature permits even heat transfer, more uniform storage temperatures, and minimizes local overheating. It is desirable to keep the glue covered so that evaporated moisture will be returned to the glue pot and thereby maintain a more uniform mixture.