Tony Hansen on sun 31 may 98
Might I be so bold as to suggest this web page:
If you can calculate the oxide formula of your own glazes and do
a couple of simple tests you will
be in the best good position to defend your use of them.
T o n y H a n s e n email@example.com
Don't fight the dragon alone http://digitalfire.com
Calculation/Database Software for Ceramic Industry
Edouard Bastarache Inc. on sun 7 dec 03
if your kiln is well ventilated you may forget about
inhaling hazardous concentrations of manganese fumes
as per a study conducted in BC, Canada:
"AUTHOR: Bob Hirtle; Kay Teschke; Chris van Netten; Michael Brauer
TITLE: Kiln Emissions and Potters’ Exposures
SOURCE: American Industrial Hygiene Association Journal v59 no10 p706-14 O ’
The magazine publisher is the copyright holder of this article and it is
reproduced with permission. Further reproduction of this article in
violation of the
copyright is prohibited.
Some ten thousand British Columbia potters work in small private studios,
cooperativefacilities, educational institutions, or recreation centers.
been considerable concern that this diffuse, largely unregulated activity
involve exposures to unacceptable levels of kiln emissions. Pottery kiln
emissions were measured at 50 sites—10 from each of 5 categories:
professional studios, recreation centers, elementary schools, secondary
schools, and colleges. Area monitoring was done 76 cm from firing
kilns and 1.6 m above the floor to assess breathing zoneconcentrations of
nitrogen dioxide, carbon monoxide, sulfur dioxide, fluorides, aldehydes,
aluminum, antimony, arsenic, barium, beryllium, boron, cadmium,
chromium, cobalt, copper, gold, iron, lead, lithium, magnesium, manganese,
mercury, nickel, selenium, silver, vanadium, and zinc. Personal exposures
to the same metals were measured at 24 sites.
Almost all measured values were well below permissible concentrations
for British Columbia work sites and American Conference of Governmental
Industrial Hygienists (ACGIH) threshold limit values (TLVs) with the
following two exceptions. A single firing duration (495 minute) acrolein
measurement adjacent to an electric kiln (0.109 ppm) exceeded these
guidelines. One 15-minute sulfur dioxide measurement collected adjacent
to a gas kiln (5.7 ppm) exceeded the ACGIH short-term exposure limit.
The fact that concentrations in small, ventilated kiln rooms ranked among
the highest measured gives rise to concern that unacceptable levels of
contamination may exist where small kiln rooms remain unventilated.
Custom designed exhaust hoods and industrial heating, ventilating, and
air-conditioning systems were the most effective ventilation strategies.
Passive diffusion and wall/window fans were least effective."
Personal sampling gave the following results <0.002 to 0.174 µg/m
of Mn while the standard is 1 mg/m3 for fumes in Quebec.
Good to see you are back.
"Ils sont fous ces quebecois"
John Hesselberth on sun 7 dec 03
On Sunday, December 7, 2003, at 05:49 PM, Marianne Lombardo wrote:
> Does firing at ^10 versus ^6 make glazes high in manganese safer?
> Someone told me it did, but I doubt it, and would like to hear from
> those who know.
No. It is the potter handling manganese dioxide that is the most unsafe
part--and that can be done safely with a proper mask and good studio
hygiene. Also breathing the fumes that come off during firing. That
presumably would be worse at cone 10, but again a well ventilated kiln
area should take care of it. Your 'someone' is not well informed.
Marianne Lombardo on sun 7 dec 03
Does firing at ^10 versus ^6 make glazes high in manganese safer? =
Someone told me it did, but I doubt it, and would like to hear from =
those who know.
Omemee, Ontario, Canada
sdr on sun 7 dec 03
....Does firing at ^10 versus ^6 make glazes high in manganese safer?.....
The main danger from manganese is not AFTER it is fired in the glaze. It
is a) in the firing - the potter can (and often does) inhale the manganese
fumes - no quicker way to get it dispersed throughout the body. And,
b) airborne manganese particles are eventually in the studio air, and
in, same as above.
I believe manganese is NOT absorbed through the skin, as some heavy
Earl Brunner on sun 7 dec 03
Marianne, first you have to understand how and under what conditions
manganese is dangerous. Shoot they are using it in the place of lead as
a gas additive. If I immerse my head in water long enough, even water
is dangerous. (I know, I know, someone out there is saying about now,
that sounds like a good idea, Brunner go soak your head, but that's just
wishful thinking on your parts, I ain't a gonna do it). My
understanding is that BREATHING manganese fumes are the problem, NOT the
fired glaze. It's more of us using it and handling it that is the
problem, not to the end user of the pots. So I don't see where the
concern between 6 and 10 is.
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Marianne
Sent: Sunday, December 07, 2003 2:50 PM
Subject: Safe Glazes
Does firing at ^10 versus ^6 make glazes high in manganese safer?
Someone told me it did, but I doubt it, and would like to hear from
those who know.
Omemee, Ontario, Canada
Stephen on mon 8 dec 03
So what are the dangers of manganese? I mean the actual results of
manganese poisoning? Would the fumes linger after several hours of cooling?
L. P. Skeen on mon 8 dec 03
Manganese causes neurological symptoms very similar to Parkinson's disease.
Monona Rossol can tell you all the particulars, but you'll need to look at
the archives to find her email address, or look her up in CT. This has been
discussed before, as well, so the information is also in the archives. The
URL for the archives is at the bottom of every Clayart posting. Good luck!
----- Original Message -----
> So what are the dangers of manganese? I mean the actual results of
Charles Moore on mon 8 dec 03
I might also add that Monona Rossol has a very thorough text: "The Artist's
Compete Health and Safety Guide"; Allworth Pres, NY, 3rd Edition, 2001.
----- Original Message -----
From: "L. P. Skeen"
Sent: Monday, December 08, 2003 5:10 AM
Subject: Re: Safe Glazes
> Manganese causes neurological symptoms very similar to Parkinson's
> Monona Rossol can tell you all the particulars, but you'll need to look at
> the archives to find her email address, or look her up in CT. This has
> discussed before, as well, so the information is also in the archives.
> URL for the archives is at the bottom of every Clayart posting. Good
Snail Scott on mon 8 dec 03
At 05:49 PM 12/7/03 -0500, you wrote:
>Does firing at ^10 versus ^6 make glazes high in manganese safer?
Not necessarily. It's still a matter of whether it's
a stable glaze. The big hazard of manganese is the
firing fumes, though. A stable manganese-containing
glaze at either temperature should be no problem.
piedpotterhamelin@COMCAST.NET on mon 8 dec 03
I always like Snail's advice and wish to add just one more thing that I read earlier on ClayArt. If release levels are unavailable then refer to the ppm limits for drinking water.
So now you must consider exposure while making the glaze, during glazing, air contamination from both air born glaze dust and the kiln fumes and the ppm released by the glaze.
Maybe I should be an origami artist.Maybe feather art.
Or heck, this job is well worth it.
"Many a wiser men than I hath
gone to pot." 1649
> At 05:49 PM 12/7/03 -0500, you wrote:
> >Does firing at ^10 versus ^6 make glazes high in manganese safer?
> Not necessarily. It's still a matter of whether it's
> a stable glaze. The big hazard of manganese is the
> firing fumes, though. A stable manganese-containing
> glaze at either temperature should be no problem.
> Send postings to firstname.lastname@example.org
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
> Moderator of the list is Mel Jacobson who may be reached at email@example.com.
Ron Roy on wed 10 dec 03
The other posts on this subject are right - the powder and the fumes are
dangerous for the potter over time. Injestion does not seem to be a
I can say that at cone 10 I think there will be more danger as the fuming
at higher temperature will be greater.
I talked to one potter recently who was using Manganese as a colour on clay
to darken it but she said she no longer uses it. I asked why and she said -
she was starting to get some of the symptoms of manganese poisoning - I did
not have time to ask anymore questions.
>Does firing at ^10 versus ^6 make glazes high in manganese safer? Someone
>told me it did, but I doubt it, and would like to hear from those who
>Omemee, Ontario, Canada
15084 Little Lake Road
Ron Roy on wed 10 dec 03
The facts are - the majority of kilns are not well vented - and those that
are can be - on occasion - not functioning well because of wind direction,
plugged vent holes, holes in exhause ducts and inadequate air replacement.
I was firing a small electric kiln in my studio the other day firing a
bisque load - vent system on, had a sensitive CO detector on, window open a
crack as it was cold outside - vent was on - controller said 550C - CO
detector reported 5 ppm CO.
Opened the window more and CO detector went to 0 almost immediatly.
It's not a small studio but the build up occured in a very short time - I
was surprised how open the window had to be to suppy enough replacement
oxygen - and in this case the wind was blowing the right way to help the
replacement air into the studio.
>if your kiln is well ventilated you may forget about
>inhaling hazardous concentrations of manganese fumes
>as per a study conducted in BC, Canada:
15084 Little Lake Road
lili krakowski on thu 30 jul 09
In the Archives, Dec 27, 28 of 2007 I cited a list from "Clay Times" in =
which Monona Rossol published a list of safer glaze ingredients, =3D
compiled by some potter.
Ron/John's book is a very useful guide to safer glazes. There is, =3D
however, an ongoing difference of opinion on the List, as well, I am =3D
sure, as in the "real world", about when , where, toxidity/safety =3D
Some ingredients are or can be harmful when they are inhaled. Others =3D
when they get on the skin. Others are harmful while being fired, as =3D
toxic fumes. gases escape. Some are all around threats; others only =3D
under certain circumstances.
I think four things of major importamce.
1. Know what is what, wear your mask and gloves, label and store all =3D
materials carefully, keep the glaze room spotless. Do not wear clothes =3D
or shoes covered with glaze material dust into your car or house...
2. Keep certain materials, such as barium, out of classrooms (yes, even =3D
adult classrooms) and, IMO out of any place where children might get to =3D
them. It is NOT amusing if a child wanting to look like Shrek paints =3D
chrome all over....
3. Understand that older books--even older versions of books that have =3D
been re-issued or re-edited--can contain recipes for materials we no =3D
longer use. The original edition of Rhodes has lots of raw lead glaze =3D
recipes in it. So does Leach...ALWAYS CHECK old recipes against the =3D
latest health and safety guides.
4. Understand that much of the stability of a glaze comes with proper =3D
firing. You have a glaze, fired to right temp it withstood the =3D
dishwasher as well as the lime juice test---in your next firing the kiln =
underfires. but the glaze looks even better than at maturity. "Aha!" you =
cry (naively, of course) that is how I will use it from now on. Just be =
aware your safety tests were NOT performed on this specific glaze, but =3D
one with same ingredients, amounts of material, BUT NOT FIRED THE SAME. =
NOT same! RE TEST
Be of good courage