338 PAINTS AND PAINTING 



as well to linseed oil that has weathered as to a good paint. Linseed 

 oil gives better results if applied hot to the metal. Another advantage 

 of using oil as a priming coat is that the erection marks can be painted 

 over with the oil without fear of covering them up. Red lead paint 

 toned down with lampblack is probably used more for a priming coat 

 than any other paint ; the B. & O. R. R., uses 10 ozs. of lampblack to 

 every 12 Ibs. of red lead. 



Without going further into the controversy it would seem that 

 there is very little choice between linseed oil and a good red lead paint 

 for a priming coat. 



Finishing Coat. From a careful study of the question of paints, 

 it would seem that for ordinary conditions, the quality of the materials 

 and workmanship is of more importance in painting metal structures 

 than the particular pigment used. If the priming coat has been prop- 

 erly applied there is no reason why any good grade of paint composed 

 of pure linseed oil and a very finely ground, stable and chemically non- 

 injurious pigment will not make a very satisfactory finishing coat. 

 Where the paint is to be subjected to the action of corrosive gases or 

 blasts, however, there is certainly quite a difference in the results ob- 

 tained with the different pigments. The graphite and asphalt paints 

 appear to withstand the corroding action of smelter and engine gases 

 better than red lead or iron oxide paints; while red lead is probably 

 better under these conditions than iron oxide. Portland cement paint 

 is the only paint that will withstand the action of engine blasts, and its 

 use is now entirely in the experimental stage. 



Conclusion. It is urged against red lead paint, that the oil and 

 the lead form a lead soap which is unstable ; against iron oxide paint, 

 that since the paint contains more or less iron rust it is necessarily a 

 promoter of rust ; against graphite paint, that there is not enough body 

 in the pigment to make a substantial paint ; etc. There is more or less 

 truth in all the accusations made against the different kinds of paint, 

 if the paint be bought ready mixed, or if made out of poor materials ; 

 however, with a good pigment and pure linseed oil, none of the above 

 objections are of weight. 





