Thanks for the feedback on spelter smelters:-)
I found this entry (via Google:-) which explains it well.
Thanks, Romilly.
Spelter, what is it ?
The town of Llansamlet , about 2 miles north east of Swansea, and in that county borough, overlooks the wide lower valley of the river Tawe. There are collieries, copper and tinplate works here, but the place is noted chiefly for its spelter undertaking, which is said to be the greatest in the country.
To the vast majority of people, spelter is a puzzle; they have no idea what it is, or what is done with it. It is really zinc, and originally one of its chief uses was for galvanising , by providing a coating impervious to weather conditions on any sheet iron dipped in a molten bath of it. It has now a myriad uses ; zinc ozide for paint, zinc chloride, sulphide, peroxide etc. Concentrates, or spelter ore, which looks like a brown dust, is imported from Australia, and the first process is to draw off the sulphur, resulting in the making of concentrated sulphuric acid. The desulpherated ore, mixed with coal and salt, becomes blende , which, passed through retort process, pours out like a silvery or bluish-white liquid, the actual spelter. This solidifies in square moulds and is zinc.
[Glamorgan, Its History and Topography by C J O Evans, 1938. Gareth 4 June 2001 G]