510 IOWA DEPARTMENT OF AGRICULTURE 



considerable difficulty to mix such a powder uniformly with oil so as to 

 have every particle in contact with the vehicle. On this account it is 

 generally considered much easier to make up a paint from the paste 

 pigments than from the dry, because the former have already been 

 ground in a small amount of oil in a mill. When a can of paste pigment 

 is opened all of it should be used immediately or it should be mixed with 

 some oil and kept covered, since the paste is likely to harden and will 

 then be ruined if exposed. 



A very satisfactory hand paint mill can be bought for less than $10, 

 and with such a mill the dry pigments may be mixed with oil and very 

 satisfactory paints made directly. The claim is made, however, that 

 many pigments require grinding under very heavy pressure to give the 

 best results. Painters, therefore, generally prefer the use of paste pig- 

 ments rather than the dry for most of their paint mixing. Besides the 

 method of making up paints from the pigments, either dry or in paste 

 form, with the necessary vehicle, the use of ready-mixed paints is very 

 common, and for a small job they have an advantage, for no paint can 

 be made properly without a large amount of grinding or stirring, and this 

 is rather heavy work. The user of mixed paints, however, should have 

 some method of estimating what the material he buys is really worth. 



COMPOSITION OF PAINTS AND THEIE COST. 



General Discussion. 



It would probably not be denied by anyone that a better paint can be 

 made in a well-equipped factory than by any individual at home or in a 

 small shop. Many ready-mixed paints are of the very best quality, but 

 many are of poor quality, made of cheap materials, and at the same time 

 are sold with extravagant claims and for high prices. The number of dif- 

 ferent formulae found on the market is enormous, and no attempt will be 

 made to give a complete or even a representative list of them. An ef- 

 fort will be made, however, to give a few typical formula of paints and 

 the methods of calculating the cost of making paints whose composition 

 is known. A very good rule to follow in purchasing mixed paints is to 

 buy nothing which does not bear the name of the manufacturer. If the 

 manufacturer's name does not appear on the label this is very good pre- 

 sumptive evidence that he is not particularly proud of his product. Many 

 State laws require that the composition of paints should also be stated 

 on the labels, and a large number of the best manufacturers do this 

 whether their products are sold in a State requiring such labeling or not. 



The most expensive paints are generally white paints or very light tints. 

 The reason for this is that there are comparatively few white pigments 

 which have covering power, i. e., the property of hiding the surface of 

 the material painted. Samples of dry white lead and of dry whiting look 

 much alike. Both are white powders and a thin layer of each appears to 

 be practically opaque. If, however, the two pigments are mixed in oil the 

 whiting is quite transparent, while the white lead is opaque. All of the 

 cheapej white pigments are more or less transparent in oil and are, therefore, 

 deficient in covering power. White lead, zinc white, sublimed white lead, 



