STRUCTURAL PAINT TESTS 245 



of acting on oil and causing its early disintegration by saponifica- 

 tion. As a matter of fact, six months after the whiting plates 

 were exposed, crumbling of the surface appeared, and twelve 

 months was sufficient for the total destruction of the paint. At 

 this time the rusted surface of the plates which had been painted 

 with calcium carbonate, seemed not to rust as fast as those 

 plates which were exposed without paint coatings, and the rust 



Plate Showing Effect of Chemically Active Pigments on Oil 

 after One Year's Wear 



which had formed appeared to be of an even, fine texture. On 

 the lower left-hand corner of these plates had been lettered the 

 figures "29" and. "30," using lampblack in oil. One of the 

 most remarkable things which appears on the fence to-day is 

 the perfect condition of these lampblack letters over their prim- 

 ing coat of calcium carbonate, standing out in clear relief against 

 the rusted metal. This test wojild suggest, therefore, that if 

 the surface of metal is properly protected with a pigment which 



