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Silicosis and quenching


Was: Understanding Casting Shrinkage

What gives? Is casting to be viewed like sucking unfiltered Camel
cigarettes? I will always advocate the safest and practical way to
do things. 

Todd and all others who are interested.

The danger of silicosis is real and potentially deadly. It is listed
as a known carcinogen on the MSDS and you will find a warning like
this one from R&R Ultravest on any package or directions from
investment suppliers


Contains respirable crystalline silica (RCS). Do not breathe
dust. May cause delayed lung injury (silicosis, pneumoconiosis).
The IARC (International Agency for Research on Cancer) reports
(IARC Monograph 68) there is sufficient evidence in humans for
the carcinogenicity of inhaled crystalline silica in the forms of
quartz and cristobalite from inhaled crystalline silica in the
forms of quartz and cristobalite from occupational sources. The
NTP (National Toxicology Program) reports (Ninth Annual Report
on Carcinogens) that RCS is known to be a carcinogen based on
sufficient evidence from studies in humans indicating a causal
relationship between exposure to RCS and increased lung cancer
rates in workers exposed to crystalline silica dust. Follow OSHA
Safety and Health Standards for crystalline silica. See Material
Safety Data Sheet (MSDS) for detailed "

as one of many articles on the web about it also see

Investment is roughly 80 % silica in a much more finely ground state
than your typical construction worker gets exposed to. Breathing the
dust while mixing or quenching is almost impossible to avoid. Even
wearing N95 masks is rarely enough protection because a) most people
don’t know how to make sure the fit is correct and b) the most
dangerous dust stays in the air for long periods of time after mixing
or quenching. That dust settles on every surface of the shop and
every time you sweep or vacuum it up it gets redistributed into the
air. Your investing and quenching facilities need to be properly
ventilated and tested to make sure it is working properly

Google silicosis and you will be overwhelmed with on the
topic but little relating directly to jewelry trades. The there have
been several papers written and presented to the Santa Fe Symposium
on Jewelry Manufacturing and Technology about the silicosis problem,
contact Rio Grande for on which proceedings contain
on the topic.

Saying that you have been doing something that is unsafe for many
years and have not had any ill effects is very much like saying you
have been smoking for years and haven’t seen any ill effects from
it. You are not in a position to make that assessment in an objective
manner. By the time the effects of silicosis show up it is way too
late to do anything about it.

Todd, you need to get with some occupational health experts and
learn some more about this because you teach in a school and are both
responsible for the health of your students while in the classroom
and in providing them with safe practices to protect
them throughout their career.

Are those who can only research about technique the only real
authority on jewelry making? I don't make this stuff up folks. If
you are lucky enough to ever get into some of the industry casting
facilities as I have you would see how it is done. 


I was the production manager at a casting company where we did
hundreds of flasks per week, so I have just a little practical
experience in the field.

James Binnion
James Binnion Metal Arts



Hi Todd,

I regret that you feel that a number of us are guilty of criticism
that may bring this forum into decline.

The fact is I’ve refrained from posting to correct bad advice many
times for fear that somebody would be offended and start an argument
on the forum. In these cases I’ve made contact off forum to
straighten out goofy beliefs.

This matter of quench is a far more serious matter. You are handing
out very bad advice with your “plunging so fast that no vapor or
particles escape into the air.”

I am not surprised you know someone who followed bad practice for
years and did not get Silicosis. Remember, thousands of people smoke
all their lives without getting cancer. The same thing happens with
inhaling microscopic silica. Not everybody gets sick!

I know the story of the two fellows who founded Prevest in 1954.
They made great investment powders for many years. One founder was
dead with Silicosis by 1987 and the other passed two years ago in his
90’s of old age with no signs of Silicosis. Neither fellow wore
breathing protection in quench, or any other area.

Is casting to be viewed like sucking unfiltered Camel Cigarettes? 

No Todd, quench is far more dangerous.

Are those who can only research about technique the only real
authority on jewelry making? 

No, we are in the field of developing and making technical materials
for jewelers, and as such know far more about these materials than
jewelers do, for the most part. We know little about the actual
creation of jewelry and we do not make that claim.

I didn’t read any other post, nor did I write anything that would
indicate I am an expert on Jewelry making. I did, however, attempt to
make many people benefit of good advice by correcting the very
dangerous advice you had passed on.

I don’t have a clue how to create a beautiful piece of jewelry—it
is not my field of expertise, it is yours. I am a materials guy and
feel a responsibility to the industry I serve to help put a stop to
silly home-grown ideas drawn from “I guess technology” instead of
from actual engineering study.

Todd, you are dead wrong about this and I am sorry if you must take
this as a personal attack. It is not. It is an effort to stop any
thought that there is any safety in quench–aside from breathing



Zero-D Products, Inc.


I’d just like to throw my 2 cents in & mention that I clean my shop
with a vacuum brand named Rainbow Vac, It’s not cheap, about
$1800.00. But it sucks the dust into a bowl of water & clean air
comes out the other end (Certified to be clean enough to be used in
an intensive care ward), All dust particles are deposited in the
water that You then empty. Its a fantastic vacuum, I bought one
because I was very stressed out that my toddler was following behind
me when I vacuumed the house with a regular machine & was breathing
all that dust. It works great in my shop. You could probably google
it, I know they have a show room in Long Island NY (Bayport?)

Mary R.


To all,

I have always practiced safe manufacturing procedures.

Safety is the first lesson I instruct. Always

The quenching procedure instructions I received from the technical
support folks at Ransom & Randolf. It is done that way most places I

Perhaps they have changed their recommendations.

Maybe this discussion should have been how it is done and how it
should be done. I don’t think this process will change that much even
with this persuasive argument. The casting part of the jewelry
industry has a way of doing this to code. Perhaps you could become
involved in upgrading changes.

I operate my shop as well as teach with OSHA guideline fully

I have just built my ninth manufacturing facility working with all
licensed contractors. I have passed electrical inspection, plumbing
inspection heating and ventilation inspection. I have a file from
the EPA two inches thick. OSHA regulations are fully maintained.

I quench and am safe. Your choice.

A good movie to watch is Rodney Dangerfield in Back To School.

As always best regards,
Todd Hawkinson



I did not read your original post but have read some of the replies,
and thought how I might have said many of those same things until
2001, when I was diaognosed with silicosis. I won’t bore you with
all the horror stories about the effects and the treatment, but
surfice it to say that I now use the best air filtration system money
can buy, and keep it on throughout the casting process. I have been
told that every day we live we are merely in the process of dieing,
but this is not what I had in mind as a good way to go.

Jon Michael Fuja


Hi Orchid Members

A good friend who is a respiratory therapist warned me about the
hazards of microscopic particles of any kind. The disease is called
COPD or Chronic Obstructive Pulminary Disease and it’s terrible.
Most folks get it from smoking (second hand or first hand) but all of
the garbage we inhale can and will cause it! We in the jewelry
industry breathe investment dust, polishing compound dust, wax dust,
chemical fumes, smoke from our wax pens and so on. Please use
ventilation whenever possible and protect your lungs as long as you
can. Silica dust is very dangerous and is the main reason I’ve
avoided it as much as possible for over twenty years.

Be Well, Margie

I'd just like to throw my 2 cents in & mention that I clean my shop
with a vacuum brand named Rainbow Vac, It's not cheap, about
$1800.00. But it sucks the dust into a bowl of water & clean air
comes out the other end (Certified to be clean enough to be used in
an intensive care ward), All dust particles are deposited in the
water that You then empty. 

The Rainbow Vac is not a HEPA vacuum. It will not do the job safely.
The particles that you are concerned about are so small that they
will not be thrown out of the air stream and will just flow with the
air right on through past the water trap. What you need is a vacuum
of the type used for asbestos removal they are very expensive and
this is why wet mopping and wipe down is a more reasonable solution.
Call the manufacturer and see if they will put in writing that their
vacuum is certified for removal of asbestos or respirable crystalline
silica, if not then do not trust that it is safe for this use.

James Binnion
James Binnion Metal Arts


I do tend to be more careful, and more paranoid from the posts on
this forum. However, at 60, however careful I am with diet, care
with chemicals, ect. 

Time to change the subject of this thread…Everything everybody
has said about investment is true - or almost. Yes, there is a
hazard, no it’s relatively small unless you use a lot. To me the
point to be made is about safety in general. We live in an unsafe
world, and work in a comparatively unsafe business. I’ve run several
shops, where it was my job to keep track of safety, BTW. What it
always boils down to is risk analysis, which for us usually is a
finger in the wind process. Meaning: Polishing dust is bad for you,
so are you going to put in a $25,000 clean-room ventilation system if
you polish once a week in your apartment? If you cast 4 small flasks
a week do you need to have a $10,000 filtration system? I’m not going
to sit here and say that people should be unsafe or work in hazardous
conditions, but let’s be real. As a metalsmith you will contact
acids, heavy metals, nasty solvents, much dust of all kinds, many
sharp tools and spinning and whirring devices, and you cannot
function in a cocoon, nor should you. Yes, it would be good to work
in a $250,000 facility, but it’s preposterous to suppose that
everybody making $15,000 worth of jewelry a year is going to shell
out $100,000 for safety equipment to protect them from every thing I
mentioned above. Ain’t gonna happen… Safety is a state of mind,
and a knowlege of the environment one is working in, and best
practices. I just don’t find the sort of things like, “Well, you
should have a micromotor nuclear powered ultimate filtration system
that cleans the air to 1/10 micron - they’re only $60,000” because
you ~might~ inhale a bit of dust once a week to be useful at all

  • it’s just not realistic for almost everybody. Nor do I listen to
    passive-aggressive statements like, “So, how much do you think a
    human life is worth? Heh?!?” Risk assessment. Use it. Again, the
    people who get to casting 300 flasks a week already know about those
    things. Somebody who’s casting a 1 1/2" flask a week could probably
    just open a window and hold their breath or wear a mask. Getting all
    uptight about every ppm of exhaust and smog and solvent and painting
    your bedroom and on and on will put you in the fetal position under
    your bed. Quit eating fried foods… As always, perspective.


Silicosis is a real hazard…no question there…If you cast using
investment you are at risk when you open the container of investment
and every step of the way from mixing until the point when the flask
meets the water.Vapours and particles escape all but the most
state-of-the-art systems, generally not found in the small shop… I
posted about Rainbows for cleaning particulate matter a few months
ago… though not sure if it is appropriate to this thread, as i
haven’t read the entire thing yet. Fumes generated at the moment of
quench and the micro- particles that can be cleaned after settling
on surfaces,( unless you run the rainbow continuously while in the
studio which ordinarily, unless it’s been put into a noise reducing
chamber that is attached to the surface of the polishing area,
grinding area and just for air treatment due to the noise generated
-which is often the reason most people /companies do not run their
air treatment systems as they should be run in the first place,).
Rainbows are excellent machines, second to none for cleaning, air
treatment and a few other functions that rainbow SE systems
accomplish- way beyond any vacuum cleaner or ionizer or other air
treatment system on the market for smaller scale use…

They can be had far cheaper than the price Mary listed ( i have two
resources and if anyone wants to contact me off list about them,
I’ll share, or arrange for one for you - (i do not sell them nor make
gain for making the arrangements for one for anyone), however as
for silicosis, rainbows will not prevent you getting the disease if
you have been standing over the vat for years quenching flasks and
inhaling, without the appropriate respiratory protection on your

Running the unit while doing many things in the studio though,
despite noise( which can be lessened easily), will help clear the
air, clean the air and if you like, enhance the ambient air quality
through the addition of various oil based simples and compounds that
do different things [for example, someone in the studio is sick
there’s a formula that is added to the basin of water to kill 99.9%
of the bacteria and airborne virus, and if your mood needs lifting -
and lemon, for instance, reminds you of a happy day selling lemonade
at your first stand, or grandma making it for you to quench your
thirst on vacation on a hot summer’s day, then the pure
non-synthetic oil of lemon can be added - will disperse with the
returned air and elevate your mood subconsciously, if not consciously
(in addition to the myriad properties of lemon oil itself), or if
you fancy Lavender oil , then add that ( I’m a vetiver & patchouli,
or juniper,oak moss,lemon and santal, orange& bay, or copal & vanilla
absolute &frank incense kind of person!)…and clean surfaces and
floors too]!Point is -any natural essential oil, or if you like the
company makes a number of fully synthetic scents and products that
can be added to the water in one of the various sized basins that
will make the air noticeably lighter, cleaner, and healthier- and
scented if so desired…

I have seen, recommended, and installed a number of large air
quality scrubbing systems in all manner of operations both industrial
and small scale- hands down the Rainbow is the way to go- If they
only made it in an industrial application size- and we could run it
on solar power and get the entire industrial world to turn it on in
sequence of the earth’s wind currents on one mutually agreeable day
(march 26th for instance!!!) day- I feel sure the planet’s health
would jump exponentially within that given 24 hour period…and if it
were quieter, and I were king of the universe, i would mandate that
every home and village install them and let em run, eliminating most
airborne junk relatively quickly from the planet, then run the water
leftover in the basins through various filters,reclaim the usable
stuff ( which, by the way metal particles are easily reclaimed from
the rainbow’s basins) and reuse the water for cultivating tress that
would contribute their own natural air cleaning and production to
assist the planet that is stressed way beyond its carrying capacity
as it is…


I will just add that while a HEPA filtration vacuum system is much,
much better than a normal or “Rainbow” vacuum, best of all is a
vacuum and or ventilation system that first filters trough normal
filters, then a HEPA filter and then exhausts the air outdoors.

While in theory (and when everything is working right) a HEPA
filtration system will remove those particles, if there is a filter
or seal failure, you could end up breathing what you don’t want to

Clean rooms and decontaminating systems use differential gauges,
alarm systems and trained personal to monitor the effectiveness of
the filters, most home / small businesses would not have the
instrumentation or training to be 100% sure that the system is 100%
good. Therefore exhausting to outside is the one way to be sure that
if there is any leakage or filter failure that the contaminant is
diluted (by being mixed in the air outside) to (relatively) harmless

I will also add that when listening to salescritters claims that a
vacuum or filtration system is “as good or better than HEPA” ask them
for written documentation to that effect and mention that you will be
passing it on to the OSHA (or up here in my part of Canada WCC)
inspector when they come by to show compliance (and then compare the
color of their complexion to some white gold alloy to see which is
whiter )…



Please don’t tempt nature and fail to protect yourself. We like you
and don’t even know you. LOL

A significant body of knowledge exists that points to silica in the
cristobalite form found in investment powders IS hazardous material.
Significant amounts of microscopic particles are created during
quenching. Microscopic particles are the most dangerous since your
normal, natural protection will not prevent these particles from
reaching the deepest parts of your lungs where they cannot be
expelled by normal processes ( coughing and sputum ). Anecdotal
stories about people who inhaled, indigested or otherwise absorbed
investment powders are not something you should base your life on.
This is serious ‘stuff’ that should be handled with understanding.
(sound of dead horse being beaten)

Thanks for being safe.
Paul Finelt, CIRM


Dear Margie,

Yes, you’re right about the COPD. I looked it up when a very dear
friend was recently diagnosed with it. It’s apparently an umbrella
term for a combination of emphysema with asthma. My friend has
smoked all her adult life and is very poorly with it, she’s been told
that she’ll be on oxygen within the next five years and probably dead
within ten. So if we can avoid such a debilitating illness then we
should make all efforts to do so.

Helen HIll
Preston, UK


In my ever present quest for safety and quality, I spoke with the
folks at Shop Vac. The technician indicated that their drywall vac
liner bags filtered dust particle to 0.1 micron. Airborn investment
particles are 10 microns. If you leave the foam liner in the vac and
add the drywall bag you now have a relatively low cost and safe vac
system. For the 5, 6, & 7 gallon vac the part number is #90671. For
the 10, 12, & 14 gallon unit the part number is #90672. Keeping the
airborn particles away from the breathing chamber is very important.

OK here’s the disclaimer. Some other more knowledgeable source will
certainly indicate this is wrong. Considering the cost this may be a
firs step for safety for many and not break the bank.

Stay safe,
Todd Hawkinson


Since the Reagan years OSHA and other regulatory agencies in the US
have been on increasingly restricted budgets and greater political
rather than scientific leadership which has resulted in less
oversight and less regulation of all forms of industry. The jewelry
industry is so small compared to other industries that there is very
little industry specific research or regulation. So basing your
safety program on the guidelines of OSHA alone is good enough to
keep you out of regulatory trouble but not necessarily safe. Do the

(Thwack, another blow to that poor horse)

James Binnion
James Binnion Metal Arts



Something you might think about is a Quarto Air Purifiers. These
units will clean the air 15 times in an hour and comes with the heap
filter. Your choice of tool suppliers carry these units. The size of
the room depends on which machine will work for you.

Andy The Tool Guy Kroungold
Phone 800-877-7777 ext 4194

Risk assessment. Use it. Again, the people who get to casting 300
flasks a week already know about those things. Somebody who's
casting a 1 1/2" flask a week could probably just open a window and
hold their breath or wear a mask. Getting all uptight about every
ppm of exhaust and smog and solvent and painting your bedroom and on
and on will put you in the fetal position under your bed. Quit
eating fried foods........... As always, perspective. 

Proper solutions to silica control are not necessarily expensive or
complex, I don’t do much casting anymore so I quench outside with a
N95 dust mask. I mix in front of a slot hood, cheap to build, damp
sponge and wet mop up spills. All easy to do in my situation When at
the casting shop yes we spent lots of money on hoods fans and other
equipment. Different amounts of dust production different amounts of
control equipment. Every one at every level can do it but you need
to know of the risks to realize what needs to be done to control

James Binnion
James Binnion Metal Arts


The quenching procedure instructions I received from the technical
support folks at Ransom & Randolf. It is done that way most places
I know. 

I’m expecting replies to my post of today, likely - probably along
the lines of “how dare you”… Heavy sigh… I’ve known about the
dangers of silica for more than 30 years - I’m not a newbie. Facts:
Yes, silicosis is a dangerous and serious occupational disease for
which there is no real cure. It hits the hardest in the mining,
roadbuilding, tunneling, masonry and pottery trades. An average of
250 people a year die of it annually in America - about 40 die from
bee stings. The OSHA level of acceptable concentration is 10mg/m3,
probably about 10,000 times what you’ll get from quenching a single
flask in water. There have been two reports in this thread of people
having it - one personal and one of the owner of an investment
factory - those are the first people I’ve ever heard of actually
having silicosis in my life. Is it serious? Of course it is. Should
you take reasonable precautions? Of course you should. Do we need to
get all shrill and up in arms about it? Well… Do you have a
dedicated chemical cabinet? Surely you have an OSHA approved fume
hood? A spray booth? A hazard suit for handling epoxy resins and
fiberglass? How many of you just open a can of dichloromethane and
just soak a ring in it on the shelf? That’s “Attack”, by the way - a
potent carcinogen and mutagen. It would be wonderful if we lived in a
world of idealism, but we just don’t. Probably 3/4 of the readers
here who are metalsmiths do one to many things that would never pass
government inspection, and somehow they seem to be thriving and happy
as clams. Run with scissors. It’s ok.


To all casters,

Let me explain a bit about the movie Back to School with Rodney
Dangerfield. He plays a character that, as a successful business
person, goes back to college to become closer to his son and earn a
business degree.

In the scene that I relate to he is assigned to write a paper on the
works of Kurt Vonnnegut. He decides not to do the work himself. He
pays to have it done. His professor recognized the paper submitted as
not his. The professor tells him, “Whoever did write this doesn’t
know the first thing about Kurt Vonnegut.” The next scene is Kurt
Vonnegut (the real Kurt Vonnegut in a cameo) not understanding how
this could happen considering he was the one who wrote the paper.

Please read the following letter I received from Michael Stover,
Product & Application Specialist from Ransom & Randolph regarding
investment quenching. Please keep in mind the legal consequences of
this company giving unsafe instructions for their products.

I’m finished with this thread and fully realize some will still call
me uninformed. It’s too bad there is a lot of knowledge to be shared
but it appears it’s all held by a select few.

Always kind regards,

Todd Hawkinson
Department Head
Jewelry Department
Minneapolis Community & Technical College

Dear Todd,

All end users are using a water quench system to remove
castings. Casting houses develop their own system, which
involves tanks or quench sinks. 

There are two factors to consider with the differences between
water quench and dry break-out. 

First, there are metallurgical properties to consider with most
alloys. If molds are allowed to simply air cool, alloy properties
may be compromised as well as decreased surface finish.  Some
alloys are also very soft, and if the pieces are filigree they
may become ruined. 

Second factor to consider is the environmental aspect of airborne
particles and waste disposal considerations.  Quenching
investment limits the amount of free particulates which are
trapped in the steam.  The steam can be exhausted by a small
hood or may not even be present if the sink or system in use has
such a volume the quench is instantaneous.  An additional
consideration would include local municipalities or waste
companies which may not take large amounts or any amounts of dry
powder but will take material which is wet sludge for the simple
reason they do not like excessive dust while dumping containers
of trash. 

Good housekeeping practices are essential for success and health
in the jewelry industry.  Any process which limits dust lowers
the total exposure amount and in this case water quenching is
indeed the preferred choice over dry knock-out.  This practice is
used on a daily basis world-wide in the jewelry industry. 

Michael L. Stover
Product & Application Specialist 
Jewelry & Solid Mold



I totally agree with you, I quench most of my flask outside, yes
let’s be safe but what are your chances everytime you get into a car
and drive to the local market versus anything that a jewelry shop
could cause. How many of you people that are concerned about
silicosis have rugs in your house without any non-slip mats under
them. Check the stats on how many people are severely injured every
year slipping in the kitchen or bathroom, as you say perspective.

Bill Wismar

The Rainbow Vac is not a HEPA vacuum. 

Correction, as of about six years ago Rainbow added a hepafilter to
their maching

Rose Alene McArthur