Chemical mid Physical Papers. 77 



boxes, barrels and bags have these numbers on them, and they are 

 stored in bins under their numbers. 



Employees of one department are never allowed in another, and 

 after a man has worked in one department he is barred from all 

 others. Then, too, some of the enamels are made up of several 

 different frits, melted at different times, and mixed by different men. 



In the making of an enamel the various raw materials are loaded 

 from their respective bins into small cars called "dollies." These 

 are filled to a line which approximates the correct weight, then 

 they are pulled on a scale, the beam of which is hidden from the 

 workman, and the chemist in charge indicates whether tlie load is 

 light or heavy, and the workmen correct this by shoveling on more 

 or taking some off. When each of the "dollies" is corrected so 

 that the required amount of material for a mix is in it, all are 

 dumped on a large hard maple floor, the coarser material on the 

 bottom and the finer on the top. This pile is thoroughly mixed 

 by shoveling, and is loaded into an electric elevator which hoists it 

 to its bin. There is a bin for each different kind of an enamel, and 

 a traveling bucket which holds a melt (about 1200 pounds) carries 

 the mixing to the crucible furnaces where it is melted into a liquid 

 glass. 



These crucible furnaces are regenerative reverberatory furnaces 

 like those used in the manufacture of glass, and our natural gas or 

 crude oil would be an ideal fuel for them. However, in the older 

 enameling works coal is used, and in the later ones, mainly in the 

 coal-fields, producer-gas is used as a fuel. The temperature re- 

 quired for the different enamels runs from 1000° C, for a glaze to 

 1300° C. for a ground coat, and the temperatures are measured by 

 a pyrometer, using a Herans platinum iridium thermo-couple. 

 Natural gas or crude oil as fuel would make the attaining and regu- 

 lation of these temperatures an easy matter. Each furnace will 

 give seven or eight melts a day, and is in charge of a head melter. 

 After the enamel is melted into a liquid glass a fire-clay plug in the 

 front of the furnace is pulled out and the molten enamel is allowed 

 to flow into a large tank of cold water. The contact with tliis 

 causes it to quench into very small particles. The water is drained 

 from the tanks and the "enamel frit" is left. This is shoveled into 

 pans (a certain weight to a pan) and is ready for grinding. 



In the mill-room the enamel frit is ground in large ball mills for 

 about thirty hours. These mills are cylindrical, about eight feet 

 long and five feet in diameter, and are lined with porcelain bricks. 

 The frit is put into them with an equal amount of water and several 



