RESULTS OF PITTSBURG TESTS 139 



with a sponge removed a discolored surface and showed but a 

 rather thin coating. Panel 175, representing Type C Pure 

 Basic Carbonate-White Lead, showed most marked checking 

 and was in very much the same condition as 174 and 176. Panel 

 176, representing Type A Pure Basic Carbonate-White Lead, 

 was in the same condition as the Type B and C Basic Carbonate- 

 White Leads. 



" Condition of Sublimed White Lead. Panel 178, represent- 

 ing Sublimed White Lead (Basic Sulphate-White Lead,) was 

 chalking, and the paint coat was somewhat disintegrated. The 

 chalking present on this formula, however, showed that the 

 disintegration of the paint coat had not taken place for 

 several months after the Basic Carbonate-White Leads. This 

 panel maintained good color, not being acted upon by sulphur 

 gases. 



" Blackening of Corroded White Lead. The black and gray 

 formation on all the Basic Carbonate -White Lead panels was 

 probably due to the action of sulphur gases which are present 

 in the district immediate to Pittsburg, and which may cause 

 the formation of black sulphide of lead. 



" Possibly a general conclusion from all these panels might be 

 described as a perishing of the paint coating, with the formation 

 of sulphide of lead which to a certain extent protects the coating 

 beneath it, but the perishing has proceeded to such an extent 

 that the unaltered paint coating left is but a slight protection 

 to the wood, being extremely thin. 



" The committee resolved that the detailed observations of 

 the panels could not be made and that they would not be justified 

 in making detailed comparisons between the various formulas, 

 giving the gloss, hardness, general condition, checking, etc. 

 Precision in this work at such a time was impossible, and it was 

 decided that a further period would have to elapse before such 

 a detailed comparison could be made between the various blended 

 or composite formulas on the fence. 



" Report on Colors. It was resolved that at the next inspec- 

 tion of the Pittsburg Fence, portions of the original samples of 

 the original paints used for the yellows and grays should be on 

 hand, previously painted out on small panels for comparison for 

 the deterioration of the colors on these same panels on the 

 fence. 



