CHAPTER XVIII 

 OILS, PAINTS, AND VARNISHES 



The preservation of wood and metal. The decaying of 

 wood and the rusting of metal are due to the action of air and 

 water; when wood and metal are surrounded by a covering 

 which air and moisture cannot penetrate, decay and rust do 

 not occur. Oils, paints, varnishes, enamels, and lacquers form 

 protective coverings for wood and metal. Keys and machines 

 rust in damp weather but oiled keys and machines remain free of 

 rust; unpainted fences rot, but fences carefully painted from 

 time to time remain in good condition for years ; it has long 

 been known that the best way to keep a house in good repair 

 is to paint it regularly. An iron bedstead is enameled not 

 only for the sake of appearance, but also as a protection 

 against iron rust. The metal fixtures of automobiles and 

 boats are always lacquered or varnished or protected in some 

 way from the air and moisture to which they are constantly 

 exposed. If this protective coating is scratched or rubbed 

 off, the metal begins to rust. 



Oils. There are two kinds of oils. One kind does not dry 

 when it is spread over a surface but remains smeary; for ex- 

 ample, lard, cottonseed oil, and olive oil. The other kind dries 

 when it is spread over a surface and forms a tough hard coating ; 

 for example, linseed oil and hemp oil. Oil which is put on 

 machinery as an aid to smooth running must be a non-drying 

 oil. Oil which is rubbed over furniture to protect it and to 

 improve its appearance must be a rapidly drying oil. All oil 

 which is used in paints must be of the quickly drying kind. 



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