Formulas—A German formula for a white enamel is (in kilogram equivalents) borax, 132; quartz, 152; felspar, 130; soda, 26; salt petre, 6; cryolite, 78; fluorspar, 3; magnesia. 6. An asid-resisting enamel white is borax, 74; • felspar, 100; quartz, 115; cryolite, 47; stannic oxide, 40; fluorspar, 6; soda. 20; saltpetre, 10; magnesium carbonate, 1; pure powdered glass meal, 53; clay, 12; calcspar, 6. A blue enamel formula is borax, 60.0; alumina, 3,6; felspar, 101.0; soda, 62; natural cryolite, 24.0; salt petre, 3.0; fused enamel fragmentary, 40.0; cobalt oxide, 3.0; limonite, 0.3; ferric oxide, 0.1. A black fused enamel formula is borax, 62i felspar, 120; soda, 14; ferric oxide, 8; cobalt oxide, 2; smalt, 16; limonite, 16.
The Metal and In the pro duction of steel enameled lcitchen utensils the metal should be as free as possible from sul phur, carbon, silicon or phosphorus and with a general manganese content of about 0.2 per cent. The sheets (oblong or square) run from 27 to 20 gauge. Applying as little heat as pos sible, they are circled, stamped and spun, using a lubricant that is easily eliminated. A pick ling process must, of course, cleanse the metal from impurities before the shaping is done. The additional trimmings (ears, handles, etc.) should be welded on because the enameling of riveted parts is a difficult process.
The Enameling The operation as carried on in American factories is clearly described by R. D. Landrum, an expert. This work starts in the 4c1ipping room," where the liquid enamel is placed in tanks of dish-pan fortn sunk into tables. The operator, called a aslusher,° dips the stamped steel vessel (which has been previously cleansed of all grease and impurities) into the enamel. Coming out of the ithmersion the vessel is covered with a fihn of the wet enamel, any drip or excess is elimi nated by the slusher gently swinging the object, when it is placed, bottom down, on three metal points that project from a board. After several vessels are placed on the board it is set in a rack, and, when dry and the rack full, they are conveyed to the furnace room where a bank of muffle ovens receives them. 'The temperature (about 1,000° C.) here fuses the minute powdered particles of enamel together into a glass coating covering the entire vessel, a proc ess requiring but three to five minutes. Other coats. are added, as needed, over this ground coat In a three-coat piece we wish, perhaps, three coats of white on the inside and turquoise blue outside. The ground coat enamel having dried and been passed through the oven comes out almost black, from the cobalt and nickel oxides, and the piece is left to cool. The slush
ing room operator now gives the vessel an im mersion in white enamel and adds a black "bead" or edge on the rim. This second coat still shows up grayish as the first coat penetrates through after firing, so it is subjected to another dip at the hands of the slusher in the white enamel. A spray of blue-green enamel is applied to the outside, before drying, with the aid of a wire brush, or the more np-to-date machine which acts as an atomizer. The vessel is next dried and fired again in the oven, leaving turquoise blue spots outside on the white bacicground. The next process is the assorting of the fimshed wares into *firsts?' ((seconds° and ((thirds° or job lots', according to their perfection or de fects. Imperfection in the cleaning of the original vessel may have caused minute spots to appear on the surface, due to rust or dirt. This defect can sometimes be remedied by filing the spots. off, or subjecting them to a sand-blast, and giving the vessel another coat of enamel. The discovery, or invention, of applying enamel coatings to metal ware such as kitchen utensils bathtubs, etc., in the same manner as the bad; tiles and earthen utensils which had been used by. our ,fathers was indeed opportune, for the nsing krice 'of the metal had made the process of tinmng so exorbitant that the industry was in real distress, with the certain prospect of the price of tin advancing to much higher pro portions. The iron-enamel industry has ex tended its lines into sanitary ware, hygienic im plements, chemical apparatus and numerous other branches. The growth of the industry, starting principally in France and Germany on a large scale, has extended to the United States, all m the course of about 25 years. The Ger man output, by 1909 already, was 90,000,000 kilos, employing a capital of near $15,000,000. In 1914 the Industry in Germany and Austria -Hungary etnployed in the neighborhood of 60, 000 wage earners. In the United States the 'Census of Manufactures) (1914), gives us the following interesting statistics of the sheet iron and steel enamel Industry. There were 270 factories, employing 28,731 operators. They produced goods valued at $68,979,005, and had a payroll of $15,242,586. Consult Gruenwald, J., 'The Theory and Practice of Enameling on' Iron and Steel) (translation by H. H. Hodgson, London 1909) • id., (The Raw Materials for the Eziamel Indusiry and their Chenideal Tecluiol ogy) (London 1914) • Landrum, R. D.; 'Enamels) (Cleveland 1918) ; Mil'met, L. E, 'Manuel pratique de l'emaillerie sur metaux' (Paris 1917).