LABORATORY STUDY OF TEST PANELS 153 



of black felt was fixed to the panel. This apparatus, which 

 resembles a blackboard eraser, is firmly drawn across the panel 

 in one direction for a certain definite distance, during which time 

 it gathers all the chalked surface presented by the painted wood. 

 Upon detaching the apparatus from the panel it is observed 

 that the black cloth becomes whitened to an extent proportionate 

 to the chalking that has taken place on the given area. 



After each one of the panels had been treated in the same man- 

 ner by the same operator, the black cloths were assembled on 

 one large board and photographed. A definite standard of 

 chalking was made up, and the operator was enabled to put 

 down opposite the report on each panel the degree of chalking 

 which had taken place, No. 1 representing the least amount and 

 No. 10 the greatest amount of chalking. 



Degree of Whiteness Shown by Panels. It was a very simple 

 matter to gauge the whiteness of the various panels, by compar- 

 ing them with a series of standard boards painted with three 

 coats of white paint. Florence Brand, New Jersey zinc oxide, 

 was used as the standard for whiteness and termed " No. 1." 

 In making " No. 2 " standard, to the zinc oxide was added .01% 

 of lampblack. By adding .02% of lampblack to the zinc, 

 standard " No. 3 " was obtained, and so on, increasing the 

 amount of lampblack in each case by .01%. These standards 

 were run up to " No. 30," and the various panels on the different 

 fences compared with them. The degrees of whiteness are 

 recorded in progressive numbers, No. 1 being the standard for 

 whiteness and No. 30 the darkest. The Atlantic City panels 

 ranged from 3 to 8 in the scale of whiteness, while the Pittsburg 

 panels required the use of the entire range of standards. 



Resistance to Abrasion. The apparatus used for determining 

 the abrasion resistance of a paint was made of a glass tube about 

 six feet long, having an internal bore of J inch. This was 

 supported in an upright position over a dish which held the panel 

 under test at an angle of 45 degrees. The abrasive material 

 consisted of No. 00 emery, which was dropped into the tube 

 through a funnel having a bore of 5 mm. When the emery 

 reached the bottom of the long tube it scattered itself so as to 

 strike a surface on the panel about an inch in diameter. The 

 emery was constantly poured in until the paint coating had worn 

 away, showing the bare wood. The weight in pounds of emery 



