AMERICAN INSTITUTE. 493 



with the "brush, and favorahly, also, by preveuting the absorption of the 

 liquid when the paint is spread on porous surfaces. 



Unfortunately no substances are known which completely fulfil all these 

 conditions I have named ; we cannot procure in nature, or by art, that 

 happy combination of properties which should exist together in the model 

 paint. We would like a paint which would dry to the hardness of flint, the 

 toughness and elasticity of India-rubber, the indestructibility of carbon. 

 But we can have no stich paint, and we are obliged to limit our inquiries to 

 the choice among the imperfect materials we have. 



Irj the choice of the liquid of paint, we can have but little doubt. 

 Theory and the almost united voice of practical painters, after centuries of 

 experience, have decided that, in view of its inherent properties and its 

 cost, nothing at present known can take the place of linseed oil. There 

 may be special uses of paint, where some other vehicle may be substituted 

 to advantage, yet to believe it I require other evidence than has been given. 

 We cannot reasonably look beyond the class of substances known as drying 

 oils, for a substitute ; and up to the present time, none of these has been 

 seriously proposed for general use. Volatile oils and such as rosin oils, 

 which oxydize into brittle resins, are altogether out of the question. Their 

 cheapness is only a cheat. Nor will any solution or mixture of india-rubber 

 or gutta percha, take the place of linseed oil, by re^ason of expense as well 

 as their inferior properties. Let it, then, be distinctly understood, that 

 linseed oil shall be the liquid of paint. 



As a theoretical question, the choice of the solid body in paint is a diffi- 

 cult one ; it involves some of the nicest refinements of chemistry ; but, as 

 a practical question, the inherent difi"erences of the multitude of admissible 

 substances are slio;ht enough to brine it to the narrow limit of a cousidera- 

 tion of cost. That substance which is permanent under ordinary influences, 

 and which can be powdered and ground with oil, at the lowest cost, will be 

 preferred. Do not the ochres answer to this condition ? I suggest here, 

 also, that metallic oxydes and carbonates generally have a certain aflinity 

 for oil, which renders the mixture more easy and intimate, so (hat the 

 resulting dried' paint is more compact and less disturbed by friction. The 

 peculiar property of white lead, in mixing with oil, and snch paint drj'ing 

 up to become a remarkably hard and tough body, is well understood, and 

 indicates it — notwithstan'ing its greater cost over ochres and other cheap 

 substances — as the best material for inside work which is to be exposed to 

 much friction. Lead paint, however, is not suitable for surfaces much 

 exposed to the weather. So that it may be that many or all solids which 

 are used in paint exert a peculiar chemical action ; yet I believe, except in 

 the case-of lead paints and a few others, it is of little or no practical account. 

 The ochres I should recommend for outside work. The substances Called 

 " mineral paint " are, no doubt, good enough ; but I have failed to see any 

 advantages in them over materials much cheaper. The pretensions made 

 for them are quackery. 



