Scientific American 32, 29.4.1848
Reduce into fine powder and grind together nine parts of red lead, six parts of flint glass, two arts of purified pearlash, two parts of purified saltpetre and one part of borax. This is put into a large crucible about half full and melted until a clear glass is obtained. This glass is then ground with water and the iron vessel is covered with a coating of it and then heated in a muffle in a furnace. This will melt in a very short time if the furnace is at a good heat and the iron vessel will be covered with a very fine black enamel of a shining appearance. To make it tough, it should be put into an annealing oven.
Anoter very fine enamel for iron vessels is made as follows: Twelve parts of flint glass, eighteen parts of red lead, four parts of pearl-ash, four parts of salpetre, two parts of borax, three parts of the oxide of tin calcined with common salt, and one part of the calx of cobalt. This is treated the same as described above and it makes an enamel of a beautiful color. It is well adapted for enamelling iron basins and other vessels.