TOWERS AND TANKS FOR WATER- WORK'S. 



primarily consists of a liquid as the vehicle or medium, with 

 which a base, or pigment, is in combination or solution. 



A perfect paint should be tenacious; non-corrosive; elas- 

 tic; impervious; of easy application; of reasonable covering 

 and drying qualities, and of comparative economy. 



The usual causes of the destruction of the paint-films 

 when applied to such structures as metallic iron or steel tanks 

 are expansion and contraction of the metal ; sand or other 

 sharp particles; or rain and sleet, contained in gusts of wind 

 impinging upon the paint-film ; the chemical and galvanic ef- 

 fect of light and heat, in the presence of moisture and gases, 

 and acting upon the paint-substances; the lack of adhesion of 

 the film to the metal, usually caused by the presence of moist- 

 ure upon the metallic surface previous to the application of 

 the film, resulting in "peeling," and finally the destructive 

 action of the water enclosed in the tank upon the oil, causing 

 swelling, shrivelling, disintegration, and a slumping away of 

 the film. 



Linseed-oil. However much individuals may disagree as 

 to the character of the pigment, linseed-oil as a medium or 

 liquid vehicle, which has been used since the remote ages, 

 continues the standard of efficiency. 



Linseed-oil is a product obtained from grinding flaxseed 

 to a coarse meal, which is heated and sacked, and being 

 placed under powerful presses, the oil is extracted in a crude 

 shape, and is refined by sedimentation and filtration extend- 

 ing over a period of from one to three months, becoming 

 "raw" and "commercially pure" linseed-oil, costing from 

 55 cents to 75 cents per gallon. 



"Boiled" linseed -oil costs a little more, and is produced by 

 heating raw oil to 400 or 500 degrees F., at which tempera- 

 ture the vegetable matter of the oil is attacked, at which stage 

 from i to 3# of either litharge or the red oxide of lead, some- 

 times with a small quantity of the oxide of manganese, is 



