It’s my understanding that while vapours from melting zinc are
dangerous to inhale, by the time the fumes react with the
atmosphere and turn into zinc oxide (those white flakes), they’re
rendered no longer dangerous. The reaction happens right above
the crucible, well away from being inhaled. For any zinc I might
add to alloys (and I don’t do a lot of it) I use 70/30 brass.
Relatively harmless floating zinc oxide or not, I know of too
many people personally who got metal fume fever by melting or
even reticulating brass, no fun at all. Use really really good
ventilation when working with brasses near melting temperatures.
A note too is that at least one safety book says that brasses and
bronzes may contain traces of arsenic and berylilium, both of
which are considered extremely hazardous when in fume form. I’m
not sure if they do (anyone know?), but I would say that I’m
erring on the side of caution the more I find out about melting
metals. And, a pre-alloy, as Brian said, is the way to add zinc
to an alloy. Charles
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