The
strength of the wires – strongest to weakest - seem to be in the
order of stainless steel, nickel/chrome alloy, brass, silver,
copper. The metal you choose will be related to the weight of the
piece, the available thickness of wire, and aesthetics.
All
of these are subject to fire scale or fire stain, a blackened surface
on the wire. This can be removed by abrasive cleaning of the exposed
metal. The metal within the glass most often takes up the fire scale
too. This can be reduced by thorough cleaning of the metal before
enclosing it in the glass. Coating the metal with a flux such as
borax often reduces the incidence of the fire scale too.
The
techniques of cleaning the fire scale from the metal range from
scrubbing and polishing to tumbling. The tumbling has the advantage
of hardening the softer metals such as copper, and silver.
Copper
looses much of its strength in the firing, and often needs gentle
working to stiffen it. This is where tumbling is so useful.
Pure
silver normally leaves a yellow stain on the glass. Sterling silver
- an alloy of copper and silver – is less inclined to do this.
However the exposed wire will stain the shelf and any subsequent
glass unless well supported by 1 mm or more of fibre paper.
It
is common in silversmithing to pickle silver to remove the fire scale
after any heat work.
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