run through a machine to "break it into smaller pieces, in which shape it 
is shipped as flake glue. In this or any other form, the dried glue may 
subsequently be ground and sold as ground glue. By varying the method of 
handling the glue as it comes from the evaporators the pearl glues or the 
shredded glues are produced. 
Testing Animal Glue 
The past 10 years have seen a marked improvement in the 
standardization of methods for grading animal glues for woodworking. The 
National Association of Glue Manufacturers has adopted a standard method 
of grading based upon tests of viscosity and jelly strength (8_). In 1931 
a federal specification was adopted for procurement of animal glues for 
woodworking. The grades set up in the federal specification are based on 
tests of viscosity and jelly strength (lj>_). It includes also tests for 
moisture content, pH, foaming, odor, and keeping quality and specif ..es the 
minimum requirements, considered adaptable to glues for woodworkings The 
definitely established tests and specifications afford the user of animal 
glues a method of insuring uniformity in the glue and of securing a product 
suited to his operating needs. 
The following methods for testing animal glue are taken from 
the federal specification ( 13 )» 
Viscosity 
Solutions of the glue for viscosity and jelly strength deter- 
mination shall be prepared as follows: Sufficient of the glue sample shall 
be taken (calculated from the apparent moisture content) to give 13»2 
grams of dry glue and placed in a standard wide-mouthed bottle of 150 cc. 
capacity with an inside diameter of 59 mm., an outside diameter of 66 mm. 
and a height over all of 85 mm., and fitted with a No. 9 rubber stopper. 
To the glue shall be added enough distilled water to make a total of 106.8 
grams of water, including that naturally contained in the glue. This will 
give an 11 percent solution based on approximately anhydrous glue. The 
glue and water shall be thoroughly mixed with a stirring rod and then 
allowed to stand at a temperature of 10 to 15° C. for at least k hours. 
The glue shall then be melted by bringing the samples to a temperature of 
62° C. in a water bath in which the temperature of the v/ater shall not 
exceed 70° C. The time required to bring the sample to 62° C. shall not 
exceed 15 minutes. 
The viscosity determination shall be made in a standard jacketed 
pipette viscometer or other suitable viscometer capable of expressing 
viscosity in the absolute unit of "poise." The instrument must be equir; 
to hold the glue solution at approximately constant temperature. The 
Rl+92 -3- 
