The spelter used must therefore be of a good grade, and the lead is usually first refined in a reverberatory furnace (the softening furnace).
Moreover, zinc and bismuth were confused, and the word spiauter (the modern spelter) was indiscriminately given to both these metals.
The former contains a mixture of semi-solid and molten metal, which is raked out into iron ladles and cast into plates of 66 to 77 lb weight, to be sold as "spelter."
Commercial "spelter" always breaks under the hammer; but at Poo° to 150° C. it is susceptible of being rolled out into even a very thin sheet.
Spelter production began in the United States in 1858 in an experimental way, and regular production in 1860.