(Please forgive posting this again; I sent it two days ago but
apparently it got lost. I think it’s important enough to repeat:)
To all who are following the thread about enamels, as a
glassworker (and former maker of leaded glass frit for casting)
I’d like to clarify a few points about the health hazards of
leaded and unleaded enamels:
The primary health hazard in working with powdered glass of
any kind is with inhalation of the glass dust. This becomes
permanently embedded in the lungs and chronic exposure can cause
a disease called “silicosis”. No cure, folks. If you are sifting,
use a dust mask. If you are sifting a lot, use a respirator.
Venitlation should be a positive exhaust system, drawing the
particles away from you and to the outside. Open windows are not
positive ventilation. Vacuum, don’t sweep your studio.
Regarding leaded enamels, most enamelists are under the
impression that you can get lead poisoning from inhaling leaded
enamel dust. This is not true. Of course, you don’t want to
inhale the dust for other reasons, but lead poisoning isn’t one
of them. The danger in leaded enamels is when they are heated to
the softening or flow temperature. (This point is different for
every glass.) Before that temperature, the lead ions are
chemically bound up with the silica and are “inert” (for the
purposes of getting lead poisoning). But at the flow point, the
lead begins to dissociate from the silica and becomes “free” in
the melt. At the glass flow point, some of it will vaporize into
the atmosphere. Those lead compounds will then hang around your
studio on all your work surfaces, tools, etc. No amound of
vacuuming is going to get rid of them. The more enameling you do,
the more lead will accumulate. I hate to shout here, but please
DO NOT fire leaded enamels without a positive exhaust system,
i.e. some kind of exhaust fan which vents the kiln or firing area
to the outside.
Both leaded and unleaded enamels also contain other metal
compounds which can vaporize at firing temperatures. These are
the colorants in glass. The most toxic ones are cadmium and
selenium (reds, yellows, oranges) and copper (most blues and
greens). Copper is especially volatile at firing temperatures.
But there are others you don’t want to breathe either: manganese,
chrome, tin. The list goes on. The point here is that positive
ventilation is really a must whether you are torch enameling or
kiln enameling. With a torch, you are more exposed directly to
the fumes, so it’s probably a greater concern. (I wouldn’t torch
enamel with leaded enamels under any circumstances.) But even
when firing with a kiln you risk a build up of heavy metals in
your studio over a period of time. Ventilate! Again, an open
window is not enough, firing with a mask does no good whatsoever,
and you may be having one heck of a good time layering all those
cool colors, but in the end they’re no trade-off for your health.
Just one more aside about leaded glass: it is very sensitive to
acid. Acids will leach the lead out of the glass. (You can eat
off leaded dinnerware as long as the food doesn’t contain acid.)
Along those lines, I suppose if you were inhaling a leaded enamel
the acidity of your body would also eventually leach some lead
out of the glass powder, but you’d croak of silicosis long before
you’d get lead poisoning from breathing the dust.
While we’re on safety, I agree with Pam about the AUR-92’s (vs.
didymiums). If you do a lot of enameling, I would consider the
investment in these lenses. The sodium in molten glass gives off
a wavelength called Sodium-D which is very harmful to your eyes
over a period of time. (There is a condition called
"glassblower’s cataracts" which can result.) Didymium glass
filters out much of this wavelength, but isn’t very good in the
infrared. AUR-92’s filter out much more of the Sodium-D and also
more infrared. You’ll experience very little eye fatigue. Once
you’ve used these lenses, you’ll be a convert forever.
I hope this helps clarify some of the safety issues with
leaded/unleaded enamels.
Rene