26 



Hardwood Record — Veneer & Panel Section 



September 10, 1919 



Points on Waterproof Glues 



Some Essential Matters to Be Considered in the Mixing Rooms 



A PAPER RECENTLY prepared by the Forest Prod- 

 ucts Laboratory, Madison, Wis., by S. Butterman, 

 a chemist, contains the following points on water- 

 proof glues: 



It may be found that the proportions used do not always give 

 exactly the same consistency. So long as the glue is neither too 

 thick nor too thin to spread well, however, slight differences in 

 consistency between individual batches or shipments of glue need 

 not be considered serious. Good results may be expected if the 

 glue spreads properly. Other things being equal, thick mixtures 



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BIRCH DOOR STOCK 

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YEARS OF EXPERIENCE BEHIND OUR PRODUCTS 



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MUNISING, MICH. 



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 HARDWOODS 



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We use this quality stock exclusively for our: 

 ROTARY CUT LOG RUN 

 ROTARY CUT DOOR STOCK 

 ROTARY CUT FURNITURE 

 ROTARY CUT PIANO STOCK 



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 THIN LUMBER SPECIALISTS 



REMEMBER we are specialists in 



LOG RUN VENEERS 



any thickness, any lengths up to 98 in. 



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develop higher strength than thin mixtures, and when great 

 strength is desired it is advisable to use the thickest mixtures prac- 

 ticable. 



If in mixing up a batch of glue from a new barrel or shipment 

 of some kinds of glue, it is found that the proper consistency is not 

 obtained, it is possible to alter it if attended to immediately and 

 before the glue has been removed from the mixing pot. This 

 should not be attempted on important work, unless the operator 

 fully understands his glue, and it should be entirely avoided if 

 possible. 



If the glue mixture obtained is seen before it is taken from the 

 mixing pot to be too thick to spread properly it can be thinned by 

 adding an extta part or two of water as may be required, and 

 stirring at slow speed until the water is thoroughly incorporated. 

 This holds for any casein glue. Under no circumstances, however, 

 should water be added to glue which has thickened on standing or 

 after being used a while. 



If the glue mixed is found before removing from the mixing 

 pot to be too thin, it may be thickened by carefully adding a 

 proper amount of dry glue with continued stirring. This is prac- 

 ticable only for glues in which all the ingredients are mixed to- 

 gether dry, and is not suitable for glues in which the various in- 

 gredients are added separately. The stirring should then be con- 

 tinued long enough to dissolve all the casein of the added glue. An- 

 other method which might be used is to mix a thicker batch of 

 glue and then mix the tv^ro batches together. It is far preferable 

 to avoid using either method, and with proper care it should sel- 

 dom be found necessary. 



The glue in any batch should be used up completely before it 

 begins to thicken materially. The length of time during v^rhich 

 the mixed glue can be successfully used may be found to vary with 

 different shipments. The operator must judge whether or not the 

 glue is fit to use at any time by its consistency. Tests have shown 

 that good results may be expected from a normal glue at any 

 time during its working life up to the time when it becomes too 

 thick to spread properly. 



In spreading the glue, it is important that enough be applied 

 to coat all the surface of both faces of the joint. An appreciable 

 amount of glue should squeeze out of the joints when pressure is 

 applied. As little time as possible should elapse between the 

 spreading of the glue and the pressing. The exact time which 

 can safely elapse will vary with the kind of wood being used, the 

 consistency of the glue, the amount of glue applied, the tempera- 

 ture, and other factors. In making veneer panels, it is considered 

 best practice to get the stack under pressure within ten minutes 

 or less from the time the first ply is spread. 



The minimum time the joints must be left under pressure is not 

 known. It is considered safest and best practice, however, to 

 leave the joints in the press or in retaining clamps for at least 

 three hours. After the glued material is taken from the press it 

 should be dried either artificially or naturally to remove the 

 moisture added by the glue. It is best also to allow the material 

 to stand a week or two to develop the full strength and water re- 

 sistance of the glue. The panels should, of course, be piled prop- 

 erly during the drying period to prevent warping. 



The above discussion is applicable in general to casein glues, 

 whether of the prepared type, such as Certus, Napco, Casco, or 

 Perkins waterproof glue, or of the type which is mixed by the user 

 directly from the raw materials. 



Before the ice age blnek wnlnnt yrcn- in Europe, ns is provetl by 

 fossil leaves and nuts in the geological formations of that period. 

 Evidently the advance of the ice pushed the walnut forests off the 

 land and they never returned. There is reason to believe that the 

 Circassian walnut was in Europe in the early ages of man's occu- 

 pancy in that region. 



