20 



PAINT TECHNOLOGY AND TESTS 



Petroleum Spirits. There are produced from Texas crude oil 

 which has an asphaltum base, and Pennsylvania crude oil which 

 has a paraffin base, high boiling-point petroleum spirits which 

 have come into wide use as paint and varnish thinners. When 

 such materials have the proper evaporating value, high flash- 

 point and freedom from sulphur, they are to be highly recom- 

 mended as paint thinners. The following shows the analyses 

 of a few of these materials examined in the writer's laboratory: 



PETROLEUM SPIRITS 



Benzol. " Solvent naphtha " or 160-degree benzol is a product 

 obtained from the distillation of coal tar, differing from benzine, 

 a product obtained from the distillation of petroleum. It is a 

 valuable thinner to use in the reduction of paints for the priming 

 of resinous lumber and refractory woods such as cypress and 

 yellow pitch pine. The penetrating and solvent values of benzol 

 are high, and it often furnishes a unison between paint and wood, 

 that is a prime foundation to subsequent coatings, preventing the 

 usual scaling and sap exudations which often appear on a painted 

 surface. Because of the great solvent action of benzol, it should 

 never be used in second and third coatings. The writer has 

 successfully painted inferior grades of cypress with a paint con- 

 taining benzol in the priming coat. 



Benzine. Benzine is seldom used in paints on account of its 

 rapid evaporation, which is apt to cause pinholing of films and 

 other surface defects. In paints of the dipping type where 

 rapid evaporation is essential, benzine finds its widest application. 



