Peter, thanks for the input on using insulating materials to protect part
s of school rings when sizing. There is a good product out there, not t
o be confused with the day glow goop which many people buy, try once and
then toss. I have found “Fixotherm” to work very well. I think it is
German, available from suppliers. It comes in a paper mach-like consistency.
Keep it wet in a tuna size tin, as you suggest. And for added
drama, keep a water pistol nearby to replenish the moisture as it dries
from heating, and also to quench the exposed portion of the metal to stop
the heat from emanating elsewhere after the work is done.
Another easy-to-find refractory mulch material is ceiling tile, the non-
asbestos boards used universally in building interiors. Chop it up and
add water, pack the piece and this too works well to keep the heat off.
Tissue works, but it burns as soon as it dries. Of course you should
not let any of these insulators dry. Keep them wet and do not cover too
much of the ring, just enough to protect the sensitive parts. Covering
more than needed will soak too much heat which is vital to the soldering