26 



Hardwood Record — Veneer & Panel Section 



May 10, 1919 



PLYWOOD 



For Makers of 



FURNITURE 

 CABINETS, CHAIRS 

 TABLES, DESKS 

 TRUNKS 

 M'OTOR TRUCKS 

 FILING CABINETS 

 INTERIOR TRIM & 

 FIXTURES 



Made of 



QUARTERED OAK 

 MAHOGANY 

 BLACK WALNUT 

 QUARTERED GUM 

 PLAIN RED GUM 

 PLAIN OAK 

 ASH, BIRCH, ELM 

 BASSWOOD & MAPLE 



Flat or Bent Work Machined or in Panels, With 

 or Without Part Cabinet Work Finished or in the White 



Send Us Your Specifications 



WISCONSIN CABINET 6? PANEL COMPANY 



NEW LONDON, WISCONSIN 



b 





glue cools too quickly and is liable to set before the joint has been 

 put into the clamps. This results in weak joints. It is also con- 

 sidered good practice to warm the wood before applying the glue, 

 but it should not be heated long enough to warp it. Wood should 

 never be glued when it is colder than room temperature, and, 

 olF course, only thoroughly seasoned wood should be used. Since 

 high-strength animal glues set so quickly on cooling, they should 

 be applied and the joints clamped as quickly as is consistent 

 with good workmanship. 



In clamping, the pressure should be evenly distributed over 

 the joint so that the faces will be in contact at all points. The 

 amount of pressure to give the best results is a question which 

 has never been definitely settled. Apparently no tests have yet 

 been made to show the best pressure to use on edge or flat grain 

 joints. In gluing veneers it is necessary to use high pressures in 

 order to flatten out the irregularities of the laminations. Pressures 

 as high as 150 pounds per square inch are sometimes used, but it 

 is not established that such high pressures are necessary or desir- 

 able. 



Strict cleanliness of glue pots and apparatus and of the floors 

 and tables of the glue room should be observed. Old glue soon 

 becomes foul and affords a breeding place for the bacteria which 

 decompose glue. The fresh glue is, therefore, in constant danger 

 of becoming contaminated. Glue pots should be washed after 

 every day's run in hot weather, and two or three times a week in 

 cooler weather. Only enough glue for a day's run should be 

 mixed at a time, so that mixed glue will not have to be held over 

 from one day to another. If these sanitary precautions are not 

 observed poor joints are liable to be the result. 



partly decomposed stock was used, or that the glue itself is decay- 

 ing. For high-grade work it is usually specified that the glue be 

 sweet: that is, it must not have an offensive odor, which is deter- 

 mined by smelling a hot solution of the glue. The odor of differ- 

 ent glues varies considerably, and it is difficult or impossible to 

 express the different "shades." It is not usually difficult, how- 

 ever, to determine whether or not the odor is clean, or, as it is 

 commonly called, sweet. The temperature and strength of solu- 

 tion are not usually specified. 



The keeping quality of a glue is determined by allowing the 

 jelly left from the jelly strength test to stand in the laboratory 

 at room temperature for a number of days. The odor and con- 

 dition of the glue are noted at intervals. Glues with good keep- 

 ing qualities will stand several days without developing an offensive 

 odor, or showing any appearance of decomposition. A more 

 rigorous test frequently adopted is to keep the solution in a 

 thermostat at about 35" C. The glue should remain sweet at 

 least forty-eight hours under these conditions. 



Glue's Odor Has Bearing On Quality 



The odor of a glue gives some indication of its source or its 

 condition. Glue which has an offensive odor is not considered 

 of the highest grade. The bad odor may be due to the fact that 



Smooth or Scratched Veneer Joints 



The common assertion that scratched surfaces make stronger 

 glued joints than smooth surfaces seems hard to prove. Com- 

 parative tests made on several occasions by the Forest Products 

 Laboratory all indicate that the strengths of these two types of 

 joints are practically the same. 



The test specimens used by the laboratory were pairs of hard 

 maple blocks, some with smooth and some with tooth-planed con- 

 tact surfaces. These blocks were glued with a high grade hide 

 glue, allowed to stand for a week, and then sheared apart in an 

 Olsen universal testing machine. Four joints of each type were 

 compared in a single test. 



Eleven tests showed that in seven of them the smooth surfaces 

 gave better adhesion. Consequently, it would seem that there 

 is no advantage in tooth-planing wood for gluing purposes. 



