Ivor and Olive Lewis on sat 21 apr 07
Dear Ron Roy,
How irresponsible of me not to give chapter and verse relating to health =
issues. Perhaps you would amplify your concern about Manganese and =
Chromium by giving data relating to Vapour Pressure of Chromium =
Sesquioxide and Manganese Dioxide..
My own technical preference would be to avoid using any colourants in a =
glaze and rely on coloured or stained slips applied to the object before =
they are bisque fired and finish with a low release transparent glazed. =
But that is not always possible.
I do use a glaze that is coloured with Chromium Sesquioxide. But I never =
hand around a kiln when it is being fired. It is the finish on many of =
Olive's mixing bowls. But only on the outside, so it is never in contact =
with food.
Have a good weekend,
Ivor
Ron Roy on thu 26 apr 07
I have no idea - but I do know the fumes are there and can be detected.
Perhaps a more interesting question would be - how much does it take to
have an effect on health - perhaps a little bird could tell us.
Chrome is a known carcinogen so I would think that would be enough warning
these days to convince anyone to take care.
RR
Ivor said: Perhaps you would amplify your concern about Manganese and
Chromium by giving data relating to Vapour Pressure of Chromium Sesquioxide
and Manganese Dioxide..
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Edouard Bastarache Inc. on thu 26 apr 07
Hello Ron,
trivalent chromium such as Green Chromium Oxide we
use
to make greens is not carcinogenic at all.
Insoluble hexavalent chromium compounds are.
Edouard Bastarache
Le Français Volant
The Flying Frenchman
Sorel-Tracy
Quebec
http://www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.orange.fr/smart2000/livres.htm
http://www.pshcanada.com/Toxicology.htm
http://www.ceramique.com/cerambooks/rayons/technologie.php
http://www.flickr.com/photos/30058682@N00/
http://perso.orange.fr/smart2000/blogs_edouard.htm
La ter,
----- Original Message -----
From: "Ron Roy"
To:
Sent: Thursday, April 26, 2007 1:32 PM
Subject: Re: : Re: Fwd: black colorants
>I have no idea - but I do know the fumes are
>there and can be detected.
>
> Perhaps a more interesting question would be -
> how much does it take to
> have an effect on health - perhaps a little bird
> could tell us.
>
> Chrome is a known carcinogen so I would think
> that would be enough warning
> these days to convince anyone to take care.
>
> RR
>
> Ivor said: Perhaps you would amplify your
> concern about Manganese and
> Chromium by giving data relating to Vapour
> Pressure of Chromium Sesquioxide
> and Manganese Dioxide..
>
> Ron Roy
> RR#4
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
>
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Ivor and Olive Lewis on sat 28 apr 07
Dear Ron Roy,
The fact that some people get pink blushing on pots placed near those =
doped with Chromium sesquioxide is good evidence of volatilisation.
Have you heard of instances where this occurred more frequently and more =
forcefully under reducing conditions? Does it happen when Iron Chromate =
is used in a glaze?
I agree that when firing that we should limit our exposure.
Best regards,
Ivor
Ron Roy on sun 29 apr 07
Hello Ivor,
I don't know what happens to chrome compounds in a reducing atmosphere.
As far as I know all the chrome oxides we use put chrome into the
atmosphere at all the temperatures we normally fire to.
I would be happy to know which - if any did not.
RR
>Dear Ron Roy,
>
>The fact that some people get pink blushing on pots placed near those
>doped with Chromium sesquioxide is good evidence of volatilisation.
>
>Have you heard of instances where this occurred more frequently and more
>forcefully under reducing conditions? Does it happen when Iron Chromate is
>used in a glaze?
>
>I agree that when firing that we should limit our exposure.
>
>Best regards,
>
>Ivor
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Ron Roy on sun 29 apr 07
Hi Edouard,
What form is the fuming chrome we find in our kilns and what form is it
when it condenses on kiln and pot surfaces?
RR
>Hello Ron,
>
>trivalent chromium such as Green Chromium Oxide we
>use
>to make greens is not carcinogenic at all.
>Insoluble hexavalent chromium compounds are.
>
>
>
>
>
>Edouard Bastarache
>Le Fran=E7ais Volant
>The Flying Frenchman
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Ivor Lewis on tue 1 may 07
Dear Ron,
All the information I have about the volatalisation of Chromium compounds
suggests that they have very low vapour pressures, meaning they are
resistant to fuming, at the temperatures we use.
But there might be an intermediate reaction we are not aware of.
Thanks for the conversation.
Best regards,
Ivor
John and Judy Hesselberth on thu 3 may 07
On May 1, 2007, at 2:48 AM, Ivor Lewis wrote:
> All the information I have about the volatalisation of Chromium
> compounds
> suggests that they have very low vapour pressures, meaning they are
> resistant to fuming, at the temperatures we use.
Hello Ivor,
Very low does not mean zero. Even with very, very, very, very low
vapor pressure, there will be a few molecules dancing off the surface
and mixing with their surroundings. That is why a piece of ice in my
freezer gradually disappears. I don't find it surprising at all that
some of our materials migrate from pot to pot a few molecules at a
time. It is also possible, though, that the active boiling we usually
see as a glaze melts results in transport that is more a propelling
of tiny particles than it is an evaporative process.
Although we are certain migration happens with lead and chromium, I
would bet we would find migration of everything we put in a kiln if
our measuring techniques were sensitive enough.
Regards,
John
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