I know that when one is melting metal with a torch that one needs to
use lenses to protect the eyes from harmful rays. But what if one is
melting metal (silver or gold) in a graphite crucible in a melting
furnace? Is there any need for such lenses in this case? As none of
the books I have make any fuss about this issue I would guess that it
is safe to look into the glowing red crucible to see if the metal is
molten and to check for undesirable sludge floating on the top. Your
feedback will be much appreciated (as I have just acquired a small
electric melting furnace).
Stan