PAINTING. 26l 



extent by the well-established facts that, on account of its 

 specific gravity being far in excess of that of the oil, when 

 mixed and spread upon perpendicular surfaces, the paint 

 " runs" or " sags," the pigment separating from the oil, the 

 coat producing a streaked appearance and not affording an 

 even covering, and it would therefore seem that its use should 

 be confined to metallic plates and shapes before assembling 

 and where the coating can be applied while the member is 

 horizontal or nearly so. 



Again, owing to the rapidity of oxidation, the red lead and 

 oil sets so quickly that it is of difficult application, but this 

 objection can be partly overcome by an addition of a carbon- 

 pigment, such as lampblack, which is an impalpable powder, 

 practically indestructible, in a measure elastic, with the 

 power of repelling moisture, and itself one of the best-known 

 preservatives of metals, but comparatively useless when applied 

 alone, from a fault in an opposite direction; that is, it takes too 

 long to dry. 



In conjunction, these two pigments modify the opposite 

 objectionable properties of each, while the fine carbon-pow- 

 der assists in filling any voids in the mass, due to imperfect 

 combination. 



In the manufacture of such paint it is a prime necessity 

 that, to produce satisfactory results, each ingredient should be 

 chemically pure, and the degree of purity will determine the 

 relative efficiency. Suitable proportions have been found in 

 20 pounds of red lead, I pound of carbon as lampblack to 

 5 or 6 pounds of raw linseed-oil. The bulk will be about i 

 gallon, with a covering capacity of about 50 square yards of 

 surface for the first coat, the film being approximately .002 

 of an inch in thickness. The cost will be about $1.50, and 

 the amount paid for labor in spreading will run about 5 cents 

 per square yard where the services of an experienced painter 

 are employed. 



