RESULTS OF PITTSBURG TESTS 147 



paint for general exterior use is made of white lead combined 

 with zinc oxide and a moderate percentage of inert pigments, 

 such as silica, asbestine, or barytes. 



" Some Peculiar Conditions Affecting the Tests. The in- 

 spectors were most impressed during the inspection by the 

 blackness exhibited to such a high degree by certain panels, and- 

 the fair degree of whiteness by others. It is Well known that 

 in Pittsburg nearly all paints become darkened by the deposition 

 on their surface of carbon particles emanating from the com- 

 bustion of soft coal. Certain of the paints, however, presented 

 fairly white surfaces, and it would thus appear that the extreme 

 darkness shown by other paints was due to their composition. 

 Corroded white lead when used alone was uniformly covered by 

 black particles, and the higher the percentage of corroded white 

 lead in a paint the darker was the surface. It was at first thought 

 that this darkness was due to the softness of the white lead 

 pigment or to its roughened surface, in causing adherence of soot 

 particles. Sublimed white lead, however, which is also a soft 

 pigment, chalked even more' progressively than corroded white 

 lead, but its surface was not rough, and presented a very white 

 appearance. Scrapings from the different panels are being taken, 

 and after a careful analysis the findings from the investigations 

 will be reported by a member of the Inspection Committee." 



A. C. RAPP. Chairman Test Fence Committee, Pittsburg Branch, 



Master Painters' Association 



JOHN DEWAR. Member Fence Committee, Pittsburg Branch, Penna. State 



Association of Master Painters 



J. H. JAMES. Chairman Carnegie Technical Schools 1 Fence Committee 



J. A. SCHAEFFER. Instructor in Chemical Practice, Carnegie Technical Schools 



Pittsburg, Pa. 



H. A. GARDNER. Director Scientific Section, Paint Mfrs. Asso. of U. S. 



May 31, 1910 



