Use of Leadless Paints.
—Opinion still differs as to the feasibility of substituting zinc sulphide or zinc oxide (or a combination of the two) for white lead in paints, in spite of elaborate investigation of the point by commissions of inquiry appointed notably by the French, Austrian, and Dutch Governments. There is, however, general consensus of opinion that for the painting of internal surfaces of houses and of all surfaces which are not exposed to the weather zinc paints have the advantage (apart from their non-poisonous quality) over white-lead paint of not changing colour. The technique for applying zinc oxide paint differs much from that for applying white lead. Being much less dense, it requires to be ground with a greater proportion of oil, and the vehicles and driers necessary for the thinning of the stiff paste are different from those ordinarily used for thinning and mixing white lead. Coats of zinc oxide should be applied as thin as possible, and hence there is the drawback that where three coats of white lead will suffice, four coats of zinc oxide may be necessary unless the paint is skilfully applied. The best method of applying zinc oxide paint with the brush has to be learnt in order to get the best effect. The ordinary house-painter, therefore, accustomed to the use of lead paint, cannot expect to obtain the same result from zinc paint treated in the same way. And zinc oxides differ in value as pigments according to the methods of production. That obtained by direct roasting of the ore (franklinite and zincite) is superior to that prepared by the indirect method of oxidation of spelter.
Zinc sulphide enters into the composition of many white paints mixed with zinc oxide, barytes, and often lead sulphate. Its defect in colour is thus concealed, and it adds to the mixture the important property known to the painter as “body.” Under a variety of names, such as “Orr’s enamel white,” “patent zinc white,” and “lithopone,” such mixtures have a large sale, and for many purposes can act as a substitute for white-lead paint.
Extensive inquiries have been made in recent years in Continental countries into the effect of use of white-lead paint in producing plumbism, the processes employed, and the possibility of substitutes—in Austria, from 1904 to 1907; in Germany, in 1905; in Holland, from 1903 to 1909; in France, from 1901 to 1909; in Switzerland, in 1904; and in Belgium, from 1904 to 1909. In 1902 the French Government, by a decree applying to house-painting, prohibited (1) use of white lead except when ready mixed with oil; (2) direct handling of white lead; (3) dry-rubbing or sand-papering of painted surfaces; and required (4) provision of the usual means for cleanliness, including overalls. This decree in 1904 was extended to all kinds of painting with use of white lead. Finally, in 1909, a law, to take effect from 1914, was passed prohibiting the use of white lead in paint altogether.
In Belgium, following on regulations issued under royal decree in 1905, in which, among other things, quarterly periodical medical examination of house-painters was required, the law dated August 20, 1909, came into force, prohibiting the sale, transport, and use, of white lead in the form of powder, lumps, or small pieces, and requiring, if intended for the purpose of painting, the white lead to be mixed ready ground in oil. Dry-rubbing and sandpapering are also prohibited.
In the German Empire the work of house-painting is controlled by regulations dated June 27, 1905, of which the following are the main provisions: (1) Prohibition of actual contact with white lead in grinding and mixing, and adequate protection from the dust so created; (2) mechanical incorporation of the white lead with the oil or varnish, and prevention of the escape of dust into the workroom; (3) preliminary moistening prior to scraping, chipping off, or rubbing down, dry oil colours; (4) and (5) provision of overalls and washing accommodation, including soap, nailbrushes, and towels (in erection of new buildings the workmen must be able to wash in a place free from frost); (7) instruction of the workman by the employer as to the risk attaching to the work by supplying him with a copy of the regulations and cautionary notice. Further, where painting operations are carried on in factories or workshops as subsidiary to other processes, there must be (8) provision of washing accommodation in a special room capable of being heated, and of a place in which to keep clothing; (9) periodical medical examination at half-yearly periods; and (10) prohibition of smoking and consumption of alcohol in the workrooms.
The Austrian Regulations, dated April 15, 1909, follow the German Code closely, but differ in that they (1) prohibit the use of white lead paint for the interior surfaces of houses or of any surfaces not exposed to the weather; (2) affixing of a notice on the can or cask that it contains lead; and (3) periodical medical examination at quarterly instead of half-yearly periods.
At the present time committees appointed by the Home Office are inquiring into the coach-painting and house-painting industries in this country.
The results of careful and detailed experiments made by the White Lead Commission appointed by the Dutch Government, which inquired into the subject, are summarized as follows:
I. Zinc-white paints are much better able to withstand the action of sulphuretted hydrogen gas than white-lead paints.