May 25, 1919 



Hardwood Record — Veneer & Panel Section 



23 



Mixing Prepared Casein Glues 



The Work Can Be Done by Machinery Better Than by Hand Methods 



7|HE GOVERNMENT laboratory at Madison, Wis., 

 has carried out numerous tests in mixing pre- 

 pared waterproof casein glues, and has embodied 

 the results in a series of notes, from which the 

 following article has been compiled : 



In using any waterproof casein glue it is of the great- 

 est importance that the glue be mixed and applied 

 properly; otherwise unsatisfactory results will be ob- 

 tained. Each glue, furthermore, differs more or less 

 from the others and may require certain differences in 

 manipulation. 



In using waterproof casein glues, the mixers used 

 ordinarily for animal glue and vegetable glue are gen- 

 erally not very successful, as a more rapid and thorough 

 stirring than these mixers give is necessary. It is possible 

 that some types of ordinary glue mixers can be speeded 

 up enough to give good results with casein glues, but they 

 have additional disadvantage in being rather difficult to 

 keep clean. The most successful mixer so far found for 

 these glues is the power cake mixer, such as is used by 

 bakers, or machines constructed on a similar plan. These 

 machines have several speeds and mix the glue in a de- 

 tachable kettle which is easily cleaned. They can also 

 iTiix relatively small quantities so that no batch of glue 

 needs to stand very long before being used up. Copper, 

 brass, or aluminum vessels should not be used for mix- 

 ing casein glues, as the alkali in the glues attacks these 

 metals. It is advisable also to equip the glue pot with a 

 metal hood fitted with a feed hopper in order to prevent 

 spattering outside of the glue pot during the course of 

 mixing. 



PREPARATION OF THE GLUE 

 It is advisable, in all cases, to mix thoroughly the con- 

 tents of a freshly opened barrel of prepared glue, and 

 preferably several barrels should be mixed at once be- 

 fore any of the dry powder is v^^ithdrawn for use, in order 

 to counteract the segregation of ingredients of varying 

 specific gravities which may have occurred during ship- 

 ment from the factory to the point of consumption. This 

 mixing may be accomplished by transferring the contents 

 of the barrels to a box of suitable size in which the dry 

 glue is turned over a sufficient number of times and 

 thoroughly mixed with a clean shovel. 



It is necessary to caution against the practice observed 

 in some plants of sifting the powdered glue and dis- 

 carding from it the coarse matter which remains upon 

 the screen. This may remove from the glue an essen- 

 tial ingredient and thus defeat the purpose for which 

 the glue is intended. 



The proportion of water to mix with the dry glue 

 should be as directed by the glue manufacturer. It is to 

 be borne in mind, however, that fixed proportions, satis- 



factory for each and every barrel of glue received, can 

 not be specified, because of a slight lack of uniformity 

 which may exist in the product. Hence, only average 

 proportions can be stipulated by the manufacturer; and 

 the operator, in order to obtain satisfactory consistencies, 

 may find it necessary at times to vary from the average 

 proportions specified. It has been found in some cases 

 that using exactly the same proportions of glue and 

 water, the glue from one barrel may be thinner than 

 that from another. It is hoped that this difficulty will be 

 overcome before long by improved manufacturing 

 methods, but until it is, much will have to depend upon 

 the judgment of the operator. It should also be remem- 

 bered that some classes of work require thicker glue 

 than others. 



.\ MECHANICAL DEVICE FOR MIXING (iH'K 



