English authorities (Thorpe, Oliver) propose diminution of the lead in the glaze in such a way that on shaking with weak acid not more than a specified small quantity shall be dissolved (Thorpe test). In my opinion such a measure is hardly enough for the small industry. I do not expect much good from obligatory use of fritted glazes.
In addition to earthenware, manufacture of tiles and bricks leads not infrequently to cases of lead poisoning from use of lead glaze.
The following measures apply to the larger ceramic works. Since risk is considerable, not only in glost placing but also in grinding, ware-cleaning, &c., closed ball mills in grinding and locally applied exhaust ventilation in ware-cleaning operations, &c., must be arranged. Personal cleanliness and proper equipment of a factory in all the essentials insisted on on pp. [226-9] are important, but nothing can take the place of efficient locally applied ventilation.
Vitreous enamelling of household utensils, baths, gas stoves, signs, &c., is an analogous process as enamels containing lead may be used. Sieving on the dry powder and brushing off superfluous glaze often cause poisoning. Here generally the same preventive measures apply.
[In Great Britain the china and earthenware industry is placed under Regulations dated January 2, 1913, which supersede the previous Special Rules. These Regulations—thirty-six in number—provide, among other usual provisions, (1) for efficient exhaust ventilation in (a) processes giving rise to injurious mineral dust (fettling and pressing of tiles, bedding, and flinting, brushing and scouring of biscuit) and (b) dusty lead processes (ware cleaning, aerographing, colour dusting, litho-transfer making, &c.); and (2) monthly periodical medical examination of workers in scheduled lead processes.]
In the Netherlands, in consequence of lead poisoning in porcelain works, committees were appointed to inquire into the subject in 1901, 1902, and 1903.
File Cutting
(See also p. [140])
In file cutting the file is cut on a lead bed or a bed of an alloy of zinc and lead. The same source of poisoning occurs in other industries such as amber working. Lead poisoning among file cutters is pronounced. The best preventive measure is substitution of a bed of pure zinc for lead. The German Imperial Health Office have issued a ‘Warning notice’ for file-cutters.
Leaflet for File-cutters