A great deal is said today of the adulteration of food products and drugs. Second only in importance are the frauds practiced in the paint trade. In point of magnitude they surpass the first. White lead, innocent of a trace of lead, is sold; one sample, bearing a label stating that $1000 would be paid if the lead in it was not pure, was found to contain no lead whatever.
The labor in painting is from two to four times the cost of the material. It is evident, therefore, that while the use of an adulterated paint works to the advantage of the painter, in that it makes frequent painting necessary, the house owner can ill afford any but the highest grade of materials. Many look only at the first cost, and imagine that a few dollars saved in the cost of the paint is so much money gained. This is due to ignorance.
The white pigments are of the most importance, as they form the basis of most paints and are often used for a first coat. Of these, white lead stands pre-eminent.
An easy test, requiring no chemical skill, is the blowpipe. A piece of close-grained charcoal is obtained, and in this a small hole is dug out. A fragment of the white lead, about the size of a small pea, is placed in this hole. "With a common jeweller's blow-pipe a jet of flame is directed against the white lead, using the flame of the spirit lamp or a small gas flame. A pure white lead will melt down to a clean button of metallic lead, leaving no residue in the charcoal. The presence of adulterants will prevent this, and instead of getting a button a grayish white moss is obtained.
Another simple test is to treat the dry white lead with diluted nitric acid. If pure, it dissolves completely, with effervesence, to a clear liquid. If a lead in oil or mixed paint is to be examined, the oil should be first extracted by thinning down with benzine. The pigment settles to the bottom, and the benzine carrying the oil may poured off the top.
To cheapen white lead, barytes, whiting, terra alba, clay, silica, and zinc white are added. The latter, however, is said to prevent the chalking of lead. Any or all of these substances may be found in a mixed paint. The prudent buyer will do well to steer clear of mixed paints; he should purchase the proper ingredients and have the mixing done on the premises.
White lead may be bought absolutely pure in paste form, with 10 per cent of linseed oil. The manufacturers of white lead are not, as a rule, paint manufacturers, and if the lead is bought from the original maker, branded with his mark, there is no danger.
The paste lead is thinned with pure linseed oil; 5 to 10 per cent of a good light colored drier is added, together with the proper tinting material, and the mixture strained through a sieve before use. No turpentine or benzine is necessary.
An important saving can thus be effected. White lead is sold at a small margin of profit. The same is true of linseed oil, so that one who does his painting in this way is often able to find that he has obtained the best of materials at less than the cost of adulterated mixed paint, on which the manufacturer nets a large profit.-" Municipal Journal."