Is there any time during the casting process when casting investment
stops being a health hazard? I wear a respirator to do the initial
investing of flasks, and run the shop’s air vent system for a couple
hours after that process is complete. But I recently heard that the
man from whom we bought all our shop equipment was diagnosed with
lung cancer. He never smoked, and he did not do any of the investing
for their shop–his wife did that. But he did all their flask
quenching and cleaning for almost 30 years. Does investment still
pose a risk to lung health after it’s solidified, burned out and
Feathered Gems Pet Motif Jewelry
Does investment still pose a risk to lung health after it's
solidified, burned out and quenched?
From what I’ve read, I’m under the impression that quenching a flask
may be one of the most dangerous operations in terms of putting very
fine, sharp, silica particles into the air. The burnout operation
alters the structure of the silica particles to be, for want of a
better, correct, term, “new”, and sharper, or something of the sort.
Particles get carried into the air in the steam developed by
quenching. Most of the particles that you see in the air when
initially mixing the dry investment powder with water are too large
to be a problem, and settle out quickly. It’s the sized stuff you
CAN’T see that’s the problem, and quenching apparently is very good
at putting that into the air, or so I’ve been told… I’m actually
more careful to wear a good respirator when quenching flasks than
when mixing the investment initially, though I try to remember to
wear one then, too.
Casting plaster, “Investment” must not get into the lungs. Whether
mixing, weighing, or quenching, a respirator is a must. I do not have
much faith in "dust masks’ due to the very small nature of some of
the particles. Silica is a big factor, but none of the typical
ingredients for investments are good for ones health. When quenching,
the steam that comes up is a health threat. Keeping the hot flask
completely under the water reduces the threat, but the respirator
must be worn anyway. The plaster, or something else might have caused
your friends’ lung cancer entirely. The doctor may know how to test
for the actual cause.
There are no metals or dusts that belong in our lungs. Keep 'em
clean and avoid all kinds of respiratory issues. Where I live (San
Fernando Valley) , a dust borne fungus causes “valley fever” during
the Santa Ana winds. The Northridge earthquake infected many via
valley dust. Keeps us aware of how delicate lungs can be for some of
us. Daniel Ballard
It is probably most dangerous when it is quenched hot as that
fractures the fine silica in the investment and makes it even
smaller and propels it into the air with the steam and you then
breath in the sub micron sized dust particles that do the most
damage to your lungs. Proper ventilation of both the dry handling /
mixing area and the quenching area are extremely important to your
health. To read further on this the Santa Fe Symposium site has
books that have papers presented on the topic
Investment This article can be found in the 1988 Santa Fe Symposium
CONTROLS This article can be found in the 1990 Santa Fe Symposium
Is there any time during the casting process when casting
investment stops being a health hazard? I wear a respirator to do
the initial investing of flasks, and run the shop's air vent system
for a couple hours after that process is complete. But I recently
heard that the man from whom we bought all our shop equipment was
diagnosed with lung cancer. He never smoked, and he did not do any
of the investing for their shop--his wife did that. But he did all
their flask quenching and cleaning for almost 30 years. Does
investment still pose a risk to lung health after it's solidified,
burned out and quenched?
The key to the fellow’s dilemma is that he worked with investment
for 30 years. Much like long term coal miners and long term asbestos
workers, long term exposure to cancer causing agents will kill you
if you take only casual precautions. You would find out that for
most of his thirty years he wore no respirator or dust mask for. His
wife wore the mask because she was investing but he thought it was
safe.( If I were her I’d go for a pulmonary test) Years ago we
weren’t fully aware of the dangers. Now we know. Too late for him
unfortunately. That being said. Remember that investment contains
silica. Silica causes silicosis, a lung disease similar to lung
cancer and just as deadly. What you want to avoid is airborne silica
that can be inhaled. This can happen most prominently during the
investing cycle. A good respirator with a HEPA filter is a must. You
must have one the right size and also wear it properly to insure
there isn’t any leakage during use. After the flasks are invested
and wet it is pretty safe. However after curing if you are one to
clean any excess investment off the outside of the flasks before
putting them in the oven you can stir up the dust. Burnout is usually
not a problem assuming your ovens are vented. ( if they aren’t you
have bigger problems than you think). The casting process is usually
pretty passive but beware during quenching. If you quench in a
bucket of water or sink the steam cloud emerging can be laden with
silica dust. Inhaling this steam is not a good idea. The other most
important item is cleanliness. Keep you shop immaculate, especially
the investing and divesting areas. Investment dust tends to settle
everywhere and then other activities stirs it up into the air. Just
run your fingers along sills and on top of cabinets and check the
results. Always wet clean so as not to stir up the dust. If you can
afford it invest in a good HEPA vacuum to aid in keeping your shop
clean. DO NOT use a regular shop vac or vacuum cleaner as the very
fine particles of silica, which are the most dangerous, will pass
right through and be blown back into the air. Cleanliness is next to
godliness in these matters, especially if you want to avoid the
latter for as long as possible. Hope this helps.
Metallurgist, Technical Manager
Tiffany & Co.
300 Maple Ridge Drive
Cumberland, RI 02864-8707
Thank you for the replies regarding this issue. What we’re using is
an actual respirator with two very fine-particle filters, not just a
‘dust mask’. Up to now our respirator has only been used for
investing, which I do alone. My husband will be wearing a respirator
when he quenches flasks from now on, and I see that we’ll need to get
a second respirator so we can work together during this process.
Question: with a high volume blower on our ventilation system (I
believe it replaces all the air in the shop room once per minute or
faster, and vents to the outside) how long should we run the vent
fans before we remove the respirators after we’ve finished working
with the investment (quenching or investing)?
As for our friend with lung cancer, he’s already had surgery to
remove the affected portion of the lung, so I think it may be too
late to test to see what caused the cancer. Fortunately, the doctors
say he should recover completely. I hope that by starting to wear
protective gear very early on in this career, we won’t develop the
same problem he did.
Feathered Gems Pet Motif Jewelry
Most of the particles that you see in the air when initially
mixing the dry investment powder with water are too large to be a
problem, and settle out quickly.
I must question Peters response regarding investment powder safety.
It has always been my understanding that investment powder is a
carcinogenic, regardless of how large or small the particles are.
Once ingested these particles lodge themselves in the lungs and
become impossible to remove.
This subject is close to my heart right now as I’ve recently
undergone tests for emphysema. I’m told most people who get this
condition are smokers, as a non smoker I fit the 10-15% of people who
can get this condition from industrial pollutants. Following several
tests I can report my results appear to be clear for the time being,
but ongoing consultations are required. This experience has been a
wake-up call for me. Like many workers in this industry, I take
precautions, but under pressure I can get “too comfortable” with
these substances. The risk to lungs is ever present in our
workshops, most substances and materials we use have the potential
to harm them.
For a short while I was forced at 56 to seriously consider the
possibility of early retirement on medical grounds with a bleak and
uncertain future. As a result I have looked at my chemical stocks and
processes and decided most are just not worth taking the risk with.
As from this week I have safely disposed of most of them and any
process that doesn’t have a safe alternative just won’t get done.
No dought there may be those who will question and criticise my
decision and that is how it should be, however if nothing else I hope
this message makes you all think about how valuable our lungs are.
Its not much fun when they don’t work properly.
Is there any time during the casting process when casting
investment stops being a health hazard?
Quenching investment does release hazardous materiel into the air.
My understanding is that it is not so much a cancer threat as one of
I must question Peters response regarding investment powder
safety. It has always been my understanding that investment powder
is a carcinogenic, regardless of how large or small the particles
are. Once ingested these particles lodge themselves in the lungs
and become impossible to remove.
I’m not a medical professional, so of course, what I “know” is only
from what I’ve read and been told. Might be wrong. But my
understanding is that larger particles are actually more able to be
removed by the lungs, via cilia action. Also, the initial investment
particles aren’t quite as sharp, and are thus perhaps less irritating
along the way. Certainly, they’re not good to breathe, and I did not
mean to imply that investment powder wasn’t dangerous. It is, and
the labels on the products are careful to advise as such. But it’s
not the most dangerous form of silica dust. The particles released
when quenching a cast flask are considerably more irritating, and in
the size range and shape that the cilia in the lungs cannot well deal
Or so I’ve been told.
As with ANYTHING ever found on Orchid, remember that information
passed on here is usually unverified, and only as good as the source.
Often, in terms of jewelry making technology, we’re reasonably
considered experts. But we also often pass on info that’s merely
what we’ve come to believe, right or wrong.
If you’re concerned, go find properly researched, published data on
the subject, and if you’ve the time, report back to us. I’d
personally like to know what that data has to say on the subject.
Question: with a high volume blower on our ventilation system
(I believe it replaces all the air in the shop room once per minute
or faster, and vents to the outside) how long should we run the
vent fans before we remove the respirators after we've finished
working with the investment (quenching or investing)?
Hi, One point which doesn’t seem to have been covered but which, from
years involved with safety issues I know to be significant, is the
discharge of extracted ‘fumes’. If a simple ventilation system is
used in a situation like this and, particularly in a built-up area,
you may just be transferring the problem to other people and could be
ultimately liable for that. In the case of the Legionnaires disease
outbreaks (of which I have some personal experience), the casualties
are seldom the people in the affected building, but are rather those
who pass by outside. Similarly in this case, if you don’t have a
good and well maintained particle filter on the discharge from
extract fans in your casting area, you could be blowing the
microscopic particles of silica at passers-by (and maybe your
families) with some force. It may be difficult for someone to prove
in twenty years’ time that their lung cancer is a direct result of
walking past your workshop every day although I’m sure someone will
try it but, if that is a member of your family who is ‘infected’ by
working out in the yard while you are casting, would you be able to
live with yourself?
Ian W. Wright