Don Jung on sun 4 jan 98
This is to the folks who asked about what's toxic and what's not (sorry,
deleted the posts, but remembered there were some queries). I've come
across the following chart that summarizes it quite well. It may be a
bit dated, so if there are some updates and corrections ... I'm sure the
good folks with the knowledge will speak up. Here you go. Also a few
statements at the end from familiar questions that bridge the info to
the non-technical.
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Toxicity Ratings for Ceramic Materials
Toxicity ratings are determined by the effect of a substance on the
individual. Materials are taken into the body through the skin, through
inhalation(breathing) and through ingestion (swallowing).
The following chart lists cermaic materials and gives their toxicity
rating.
HIGH TOXICITY: HT: Material causes major permanent or
temporary damage or disability.
MODERATE TOXICITY: MT: Material causes minor permanent or
temporary damage or disability.
SLIGHT TOXICITY: ST: Material causes illness which is
reversible..
LOW TOXICITY: LT: Material is only toxic under abnormal
conditions.
TOXICITY TABLE
CERAMIC MATERIAL SKIN INHALATION INGESTION
TOXICITY TOXICITY TOXICITY
-------------------------------------------------------------------
ALBANY SLIP ST HT LT
ANTIMONY MT HT HT
ASBESTOS * ST HT HT
BARIUM CARBONATE ST HT HT
BENTONITE ST HT LT
BONE ASH ST ST ST
BORAX/BORIC ACID ST MT MT
CHROME OXIDE MT MT ST
CHROME YELLOW * MT HT HT
CLAY ST HT LT
COBALT CARBONATE ST MT ST
COLEMANITE / GERSTLEY BORATE MT MT MT
COPPER CARBONATE ST MT MT
FELDSPARS LT HT LT
FIRE CLAYS ST HT LT
FLINT / SILICA LT HT LT
FLUORSPAR MT HT HT
IRON CHROMATE * MT HT HT
IRON OXIDE (RED & BLACK) LT LT LT
KAOLIN ST HT LT
LEAD BISILICATE LT HT HT
LEAD CHROMATE *** LT HT HT
LEPIDOLITE MT HT MT
LITHIUM CARBONATE MT MT MT
MANGANESE CARBONATE LT HT HT
NEPHELINE SYENITE MT HT HT
NICKEL CARBONATE * MT MT MT
POTASH MT HT HT
RUTILE LT LT LT
SODA ASH MT HT HT
SODIUM SILICATE MT MT ST
TALC LT HT HT
TIN OXIDE LT LT LT
VANADIUM OXIDE MT HT HT
WHITE LEAD LT HT HT
WHITING LT LT LT
WOLLASTONITE ST MT ST
ZINC OXIDE LT ST ST
ZIRCOPAX ST HT ST
* Carcinogen: causes cancer
** Teratogen: causes fetal malformation
*** Mutagen: causes mutation
For Further information , Read: "Artist Beware", Michael McCann.
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Then there were a bunch of questions from the crowd who weren't into the
glaze ingredients, formula, mixing, etc ...
"So what does all this mean to me?"
Well, here's some answers in more everyday studio language that I've
given to the beginning student to follow until they learned enough to
make their own assessment of the risks.
* Unless you are making glazes and handling the chemicals, you probably
won't come into direct contact with any of the High or Moderate toxicity
materials. When working with chemicals, always wear an appropriate dust
mask and gloves and in an area with an extraction fan or vent.
* You should avoid getting underglazes, glazes and other colorants on
your skin. If you do, wash them off with water. Plain old clay of
course, is not a problem.
* Avoid inhaling or creating any and all dust. Work with clay that's
wet or leather hard. Do not scrape or trim dry clay. If you want to
work with it again, get it wet, use a water spray, put a wet cloth on it
and wrap it tightly for a little while.
* Always wet wipe or wash all clay and glaze splatters, splashes and
spills. Wet mop counters, floors and surfaces instead of dry sweeping
which creates dust.
* Don't taste any pottery materials and avoid food and drinks in the
studio. No smoking is permitted.
* Don't handle clay, glazes and materials with cuts or wounds that may
come into contact with the materials.
* If you are making functional pottery that comes into contact with food
or drinks, here are some things to keep in mind.
* A glossy clear or white 'liner' glaze is the best glaze to use for
food contact surfaces. We use no high or moderate toxicity (ingestion)
materials in the clear or white glazes.
* All glazes in this studio are free of lead and cadmium.
* Dark glazes (black, dark blue, dark green, dark purple) have higher
amounts of oxides and colorants. Lighter colors are more suitable for
food contact surfaces with fewer oxides that can leach.
* The browns, rust and tans are OK unless marked 'Not Food Safe'. These
usually contain iron, albany and/or rutile which are of low toxicity
when ingested.
* Glazed surfaces should be free of crazing, cracks, crawling (bare
spots), pin holes and cover the entire food contact surface so it won't
trap bacteria or cause a cut.
* Glossy glazes are generally safer than matt for food contact and
easier to clean as well.
* Multiple or mixed glazes are not advisable for food contact surfaces,
especially with the dark glazes.
* Underglazes, slips and stains are generally OK if applied correctly
and completely covered with a sufficient coating of clear glaze.
* Onglaze and Majolica decoration should be done away from the surface
that contacts food/drink.
* Leaching is much more likely to happen with acidic liquids such as
orange or apple juice, tomato sauce etc. Dry foodstuffs like nuts,
cookies etc. are not as likely.
* If at all in doubt, don't use it, ask questions, do some research
and/or take it to a lab for testing.
--
Don Jung
In cool Vancouver BC where the snow flurries are sneaking in. Time to
hop in the Hot Tub!
email: don.jung@mail.icbc.com
Diana Mannino on fri 16 jan 98
Hello Don,
Your toxicity chart is a valuable aid for me and friends that I've
passed it on to. Thanks!
I have a question. Both cobalt oxide and copper oxide were not listed
(would the carbonate be the same??) and as a friend of mine uses them
extensively, I'd like to know the rating info for her. She coats her
pots with it, scrapes them down at bit and bisque fires. She doesn't
glaze at all. (does mostly 'sculptural forms) Could bowl forms be used
for fruit or such? Would just touching the bisque piece cause any
problems? Thanks so much for your sharing.
Diana Mannino
Cortona, Italy
p.s. the reason she uses the copper is to get black on the bisque...is
there something else that's 'safer' she could use?
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