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[Enamel Bits] Leaded Enamels and Ventilation


#1

(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


#2

Hi Rene…wow, that was one of the most clear explanations of
lead in enamels I have ever heard. Thanks.

BTW…do you know where I can get the AUR-92’s? I asked the
welding place where I buy gas and a couple optical places with no
luck.

Karen


#3

Rene,

Great post! I’m saving that one. I KNEW I didn’t want to be
using leaded product. Nice to have my gut instincts verified
with some facts. g

My studio is in my garage, and other than it being a "airy"
space, I haven’t got a ventilation system. Do you think sticking
a box fan in the door blowing out would consitute a “positive
ventilation system”? Or do I need to get a roof mounted exaust
fan of some kind? As I said, I don’t use leaded enamel, but I do
occasionally fire cadmium colors.

Pam East pam@pinzart.com
http://www.pinzart.com


#4
   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.) 

Good point, but my question is: Wine is an acid, we have been
drinking wine from leaded crystal for hundreds of years! You can
buy leaded crystal anywhere in the USA. Such as Waterford. But
you can’t even use a leaded enamel on the outside of a lead free
soft drink bottle. I have been using leaded enamels for over 30
years. I keep asking my Dr. and he keeps checking me and says
there is no traces with any of the tests that have been
performed. I think most of what the government stuffs us full
of is total bunk!!! Yes, there is a danger, but with most things
the government pendulum must swing all the way out of sight,
before reason finally takes hold. Besides lead free enamels can’t
hold a candle to the real thing. But I do agree, care should be
taken. But let reason have some influence. Pat


#5

The AUR-92’s are an exclusive product of the Aura Lens corp.
You can contact them through their web site at
http://www.auralens.com/ , as well as reviewing their product
line.

Peter Rowe


#6

While you can still by leaded crystal in stores, it is now
recommended that you not store alcohol in leaded decanters, as
continued exposure over time will do what a brief stay in a glass
will not.

Kat Tanaka
@Katherine_Tanaka


#7

Karen and others- You may get AUR-92’s from Aura Lens Products
(they are the developers of the lenses, will grind them to your
prescription if you need it). They are not available from regular
dispensing opticians.Aura Lens has a Web site, but I don’t know
the URL. Peter Rowe posted quite a message on Orchid a few weeks
ago about some complimentary lenses he received. I think that
message contained all the contact info. If you can’t find it in
the Archives, perhaps he will help.

Glad you found the lead/enamel info helpful.


#8

Pam, I can’t pretend to be a “ventilation expert” about what
your individual needs might be; it depends on what you do and how
much of it you do. If you fire enamels all day or every day, your
needs are going to be greater than if you only do this
occasionally. For torchworking glass, the standard I’ve always
heard used is “six complete changes of air per hour”. This means
I had to figure out the cubic feet of studio space I have, and
look at the cfm (cubic feet per minute) rating of various exhaust
systems I was considering. But your needs are probably going to
be much less, especially since you aren’t using leaded enamels.
If you place a box exhaust fan in a door or window, it would
certainly be more ventilation than you have now. (Be sure to
crack a door or window at the other end of the studio too, so
there will be an intake of fresh air to replace what you’re
exhausting. If your studio is in a garage, the space may be
drafty enough you don’t need to do this.) The closer you can
locate this fan to your kiln, the better. You also might consider
a range hood over your kiln. These are fairly inexpensive. If you
are torch enameling, have some kind of exhaust system right at
the torch. The thing with heavy metal fumes is that they’re
heavier than air, so a more powerful fan is needed to exhaust
them than would be needed for some other things.

Hope this helps.

Rene


#9
   Good point, but my question is:  Wine is an acid, we have
been drinking wine from leaded crystal for hundreds of years! 
You can buy leaded crystal anywhere in the USA.  Such as
Waterford. 

Enamel may be a glass, but not all glasses are the same. Glass
intended for blowing into free standing transparent objects, such
as “crystal”, have a quite different formulation than enamels
which must have their expansion/contraction rates matched to that
of the metal they are to be used on, as well as having melting
points far, far, lower than that of blown glass. Most blown
glass is worked at temps closer to the two thousand degree mark
and above, while enamels are made to melt and flow below 1500.
These are crucial differences. This often means the enamels will
have componants such as borax or boric acid or various other
silicates added to the basic formula for glass that is used in
lead crystal. Also, it’s a function of the amount of lead as
well. Leaded glass such as waterford is made with formulas that
ARE, as you say, safe to drink wine from. Note though, that even
they are more prone to attack than are lead free glasses. Take a
look at waterford goblets that have spent a lot of time going
through dishwashers, which sometimes are used with fairly harsh
detergents, and you’ll find that they etch more quickly than do
plain drinking glasses made without the lead content.

Leaded enamels are made for completely different working
properties and purposes, and often will NOT be safe for that same
wine. The presence of safe lead oxide levels in the one product
does not infer safety in the other.

Peter Rowe


#10

You may want to consider an “exhaust hood” over your soldering
or firing (why doesn’t that look right??) area.

I recently had a HOOD installed in my soldering area. There are
walls of metal on three sides, and an attached hood over the top.
That way, not too much air is sucked out of my basement (where I
have a furnace and a hot water tank - both of which exhause
carbon monoxide . . . if you have too much of a back flow, the
bad fumes will re-enter your rooms!)


#11

Peter is entirely correct about why leaded glassware does not
pose the same level of hazard as leaded enamels. Blown glass
requires a much higher temperature to be workable, i.e. a
"stiffer" glass, therefore more silica is needed to bind with the
lead (and the silica keeps the lead stable). Rule of thumb with
leaded glass (intended as a general guideline only): the lower
the flow point, the more lead in the glass. This means that your
"soft fusing" enamels are going to pose more of a potential
hazard than the hard fusing ones, especially if they are
overheated. It is in the overheating that the lead is especially
prone to dissociate from the silica.

I know it’s more fun to just enamel, without all this technical
mumbo jumbo.

Rene


#12

Re inexpensive ventilation: For the many of us who do not have
unlimited funds. Ventilation in the industrial sense means
changing the air in the ventilated area at a minimum of once
every 10 minutes. In a large area, like a school shop or a
garage this would require a very large vent fan, however, by
constructing a “hood” a simple over the range type vent fan would
be more than adequate. For an enameling kiln, or for a
investment work area simply constructing a pair of partitions on
either side of the work area and install the over range hood
between these will increase the local ventilation tremendously.
Building a partial closure in the front will increase efficiency
even more. For a enclosure around a kiln one should use fire
resistant matereal.


#13

Good point, but my question is: Wine is an acid, we have been
drinking wine from leaded crystal for hundreds of years! You can
buy leaded crystal anywhere in the USA. Such as Waterford.

Several years ago 'whin I was studying chemistry, I read an
article on the storage of spirits in Leaded decanters, the
researchers found that the longer the spirits were stored the
more lead they could detect in the liquid. There conclusion was
that for an evening serving spirits in leaded decanters would not
pose any more of a risk than the alcohol itself, but these should
not be used for long term storage,

WayneM


#14
    Good point, but my question is:  Wine is an acid, we have
been drinking wine from leaded crystal for hundreds of years! 

You might want to consider this: I stored some homemade wine in a
beautiful decanter and ended up with a junky looking decanter.
The acid in the wine had etchd a fine “cloud” inside the
container. Boy, was I sorry. --kathi parker