28 



Hardwood Record — Veneer & Panel Section 



August 10, 1919 



PLYWOOD 



For Makers of 



FURNITURE 

 CABINETS, CHAIRS 

 TABLES, DESKS 

 TRUNKS 

 MOTOR 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 & PANEL COMPANY 



NEW LONDON, WISCONSIN 



Effect of Age on Casein Glues 



That casein glues can be successfully used any time after mixing 

 up to the time they become unworkable is the conclusion drawn 

 from a number of tests at the Forest Products Laboratory. 

 Ordinarily casein glues exhibit a life of from 3 to 5 hours, though 

 there are some which remain usable over a much longer period. 

 The laboratory has from time to time received inquiries as to 

 whether or not these glues could be relied upon to give as satis- 

 factory strength and water resistance after three or more hours 

 as they do immediately after mixing. 



To study this question, shear blocks and plywood panels were 

 made up hourly, starting at the time the glue was mixed and con- 

 tinuing until the glue became so thick that it was unworkable. 

 The blocks were allowed to season for 7 days and were then 

 tested in shear in the usual manner; the panels were given shear 

 tests, 8-hour boiling tests, and 1 0-day soaking tests. Results of 

 the tests on one commercial glue are shown in tables I and 2. 

 These are typical of the results obtained with other glues. 

 Table 1 . Result of Joint Strength Tests 



Average Percentage 



Age of Glue Shearing Strength of Wood 



in Hours in Lbs./Sq. In. Surface in Failure 



Vi 2,170 24 



Wi 2,137 51 



2>/2 2,276 58 



31/2 2,453 3 



5 2,098 23 



Table 



Age of Glue Condition After Condition After 



in Hours Boiling 8 Hrs. Soaking 10 Days 



1/2 O.K. O.K. 



V/z O.K. ' O.K. 



21/2 O.K. O.K. 



iVi O.K. O.K. 



.3- O.K. O.K. 



Results of Plywood Water Resistance and Strength 

 Tests 



Ave. Shear- 

 ing Strength 

 in Lbs./Sq. In. 

 261 

 289 

 349 

 294 

 257 



Effect of Number of Coats on the Moisture 

 Resistance of Spar Varnish 



Recent experiments at the Forest Products Laboratory have pro- 

 vided some information concerning the relative protection against 

 water afforded by various numbers of coats of spar varnish. 



For these experiments three varnishes were selected from about 

 forty brands tested, the first varnish being one of the best of the 

 forty, tlie second a little better than the average, and the third a 

 little below the average. From two to twelve coats of each varnish 

 were applied to panels of 3'ellow birch, which were then exposed 17 

 da.vs to a humidity of 100 per cent. Tlie results are given in the 

 accompanying table. 



Comparative Reduction in Absorption of Moisture and Swelling 

 Caused by Different Numbers of Coats of Spar Varnish Exposed 

 for a Period of 17 Da.vs in a Saturated Atmosphere: 



Xo. of 

 coats 



of 



spar 



varnish 







2 



4 



(i 



S 



10 



12 



Percentage of moisture 



excluded (based on 



untreated specimens) 



1st 

 varnish 

 n.O 

 7G.7 

 86.2 

 88.6 

 91.0 

 9.S.0 

 94.3 



2d(1 

 varnish 

 0.0 

 72.0 

 75.8 

 81.7 

 S6.9 

 S8.4 

 89.0 



3rd 

 varnisli 

 0.0 

 65.D 

 76.9 

 83.0 

 S0.2 

 .17. 3 

 .S7.2 



Percentage of increase 



in width due to 

 absorption of moisture 



1st 

 varnish 

 8.61 

 2.01 

 1.19 

 0.98 

 0.77 

 0.60 

 0.49 



2nd 

 varnish 

 8.61 

 2.41 

 2.08 

 1.57 

 1.30 

 1.00 

 0.90 



3rd 

 varnish 

 8.61 

 2.97 

 1.99 

 1.46 

 1.19 

 1.09 

 1.10 



It Viall be noted that two coats of the first varnish were about as 

 effective as four coats of either of the other two, and that four 

 coats of the first varnish were about .-is effective as six to twelve 

 coats of either of the others. The first varnish gave increasing 

 moisture resistance with each additional coat, but practicall.v 

 nothing was gained by adding more than six coats of the others. 



A small cjuantity of lignum-vitae grows on some of the Florida 

 islands but the trees are so small that the trunks are of little value 

 in a commercial wav. 



