190 PAINT TECHNOLOGY AND TESTS 



conditions also apply to those panels on the 1908 fence coated 

 with shellac as a primer. 



" The colored formulas in every case showed a great superiority 

 over the same paints in white untinted, and demonstrated that 

 a percentage of color has a wonderful influence on the preserva- 

 tion of the paint coating, reducing chalking, checking, and general 

 disintegration. This condition is probably due to the reinforcing 

 value of the color pigments used. 



11 It is safe to state that the combination formulas tinted yellow 

 were of better appearance than the corroded white leads tinted 

 yellow, the latter appearing quite dark in many cases. 



" The wearing of the paints made solely from white lead and 

 zinc oxide seemed to indicate that a percentage of a third pigment, 

 of an inert nature, would have been beneficial. 



" The high-type mixtures of pigments containing lead and 

 zinc, with moderate percentages of inert pigments, on good wood, 

 were in most excellent general condition; in fact, much superior 

 to the single pigment paints. Their surface exhibited only minor 

 checking and moderate chalking with good maintenance of color, 

 and presenting surfaces well adapted to repainting. 



" The sublimed white lead was in fair condition, with very 

 little checking, and offering a fair repainting surface. The 

 corroded white lead was somewhat whiter than the sublimed 

 white lead, but a careful observation of the surface of the corroded 

 lead revealed deep checking. 



" It was clearly demonstrated, however, that in climates of 

 the North Dakota type, white lead alone is not entirely satis- 

 factory. The addition of zinc oxide to white lead forms paint 

 that has proved much superior to the white lead alone. 



" It was conclusively demonstrated that mixtures of white 

 lead and zinc oxide, properly blended with moderate percentages 

 of reinforcing pigments, such as asbestine, barytes, silica and 

 calcium carbonate, are most satisfactory from every standpoint, 

 and are superior to mixtures of prime white pigments not rein- 

 forced with inert pigments. 



" The white leads painted out on the 1908 fence exhibited 

 different degrees of checking, the mild-process lead and sublimed 

 white lead which presented the best surfaces, being free from 

 checking, while the old-process leads seemed to show very deep 

 and marked checking, even after one year's wear. 



