Jl and J2 for general use in joint work where assembly periods are 
short. 
SI and S2 for special use in warm and humid climates where a quick 
chilling glue may he required. 
As a further guide in selecting the grade and concentration of 
glue for a particular job, the following schedule (ll_) will pre luce good 
joints when an animal glue equivalent to the J2 grade is mixed in the pro- 
portions of 1 - 2-l/h. 
Temperature of Assembly 
room and wood period 
(°F.) (minutes) 
70 1/2 to 1 
80 3 to 5 
90 10 to 18 
When the assembly period is fixed by the operation and the 
temperature in the glue room rises, an adjustment must be made to accelerate 
the speed of thickening. This adjustment can usually be made most easily by 
mixing less water with the glue. 
The above schedule of conditions can be met with a lower grade, as 
Jl for example, by mixing less water with the glue than recommended for the 
J2 grade. Likewise, a higher grade, as SI or S2, may be made to conform by 
mixing more water with the glue. Within limits, therefore, a user may pur- 
chase a glue of higher rating and mix it with more water or one of lower 
rating and mix it with less water to fit a particular operation. 
In preparing animal glue for use a number of precautions must be 
observed if satisfactory results are to be obtained. The proportion of glue 
and water should be varied to meet manufacturing conditicr.s (11 ). When the 
right proportions have been worked out they should be adhered to consistently. 
The glue and the water should be weighed out whenever a batch is prepared. 
Clean, cold water should be used and the mixture thoroughly stirred at once 
to allow a uniform absorption of water by the dry glue and prevent the 
formation of lumps. The batch should then stand in a cool place until the 
glue is thoroughly water soaked and softened. The soaking may take only an 
hour or two, or it may take several hours, the time depending upon the size 
of the particles. The glue should then be melted over a water bath at a 
temperature not higher than I5O F. High temperatures and long continued 
heating reduce the strength of glue solutions and are, therefore, to be 
avoided. The glue pot should be kept covered as much as possible in order 
to prevent the formation of a skin or scum over the glue surface. 
Strict cleanliness of glue pots and apparatus and of the floors 
and tables, of the glue room should be observed. Old glue _socn becomes foul 
RUQ2"' -7- 
