Martin Rice on wed 14 jul 04
I followed the discussion about food-safe low-fire pottery with interest. I
read the many different views, and there were truly different ones. I guess
I didn't totally come to a conclusion myself.
Then someone wrote in with a link to the Hess Pottery. This is unglazed, red
clay pottery with 4 coats of terra sig and fires to ^04. The site says the
pottery is food, microwave, and dishwasher safe.
What I didn't get from the discussion is whether any of the respondents were
reacting to this site and the claims there. I'd really love to know if
anyone has an opinion about whether this type of pot could be food safe.
Thanks,
Martin
Santiago de Puriscal, Costa Rica
Antoinette Badenhorst on wed 14 jul 04
Dear Martin,
My guess is that the terra sigilata that this guy uses fuses very well
on the clay body (the two fits well together) and that the clay body as
well as the terra sig vitrifies at o4 to a point where it is water
tight. In particularly red clay that is burnished and fired high enough
can become so smooth that it can be used as a "glaze" Some potters paint
the bottoms of their pots with terra sig to get it extra smooth.
Regards.
Antoinette Badenhorst
105 Westwood Circle
Saltillo MS
38866
662 869 1651
www.clayandcanvas.com
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Martin Rice
Sent: Wednesday, July 14, 2004 2:42 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Confused about low fire - food safe
I followed the discussion about food-safe low-fire pottery with
interest. I
read the many different views, and there were truly different ones. I
guess
I didn't totally come to a conclusion myself.
Then someone wrote in with a link to the Hess Pottery. This is unglazed,
red
clay pottery with 4 coats of terra sig and fires to ^04. The site says
the
pottery is food, microwave, and dishwasher safe.
What I didn't get from the discussion is whether any of the respondents
were
reacting to this site and the claims there. I'd really love to know if
anyone has an opinion about whether this type of pot could be food safe.
Thanks,
Martin
Santiago de Puriscal, Costa Rica
________________________________________________________________________
______
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You may look at the archives for the list or change your subscription
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Lee Love on thu 15 jul 04
Martin Rice wrote:
>What I didn't get from the discussion is whether any of the respondents were
>reacting to this site and the claims there. I'd really love to know if
>anyone has an opinion about whether this type of pot could be food safe.
>
>
Martin, He uses "safe" materials in the making of this work. It is
all RedArt. I would confidently bake pies in his pie plates as I
would confidently drink tea from a Linda Arbuckle majolica teacup.
--
Lee in Mashiko, Japan http://mashiko.org
http://journals.fotki.com/togeika/Mashiko/ Commentary On Pottery
Martin Rice on sat 17 jul 04
Just wanted to thank Antoinette, Ivor and Lee for their comments about low
fire/food safe pottery. It sounds to me that the consensus is that yes,
indeed, red clay fired to ^04, with or without terra sig can be used for
cooking. I'm working on the assumption that if that is the case, dishes and
cups, and bowls made the same way can be used for eating. If there's a
difference, that is, if this assumption is not so, I'd appreciate someone's
letting me know.
Martin
Santiago de Puriscal, Costa Rica
Where the new house we're building is now two months behind schedule and
I've had to fire the architect and builder. Now we have a new crew and think
we'll be living in the house, which is simply lovely -- log and stone -- in
three more weeks. Which, in turn means, that I'll finally be able to use my
new studio and continue making my ugly little vessels. Really difficult to
wait even these few weeks. It's been almost a year since the last time I
muddied my hands.
Antoinette Badenhorst on sat 17 jul 04
Martin, it is important to remember that not all red clays will be
vitrified at ^04 firings. This person got a clay and terra sig medium
that works perfectly well for what he is doing. Just wanted to make sure
that the difference is clear to you.
Regards.
Antoinette Badenhorst
105 Westwood Circle
Saltillo MS
38866
662 869 1651
www.clayandcanvas.com
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Martin Rice
Sent: Saturday, July 17, 2004 8:25 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Confused about low fire - food safe
Just wanted to thank Antoinette, Ivor and Lee for their comments about
low
fire/food safe pottery. It sounds to me that the consensus is that yes,
indeed, red clay fired to ^04, with or without terra sig can be used for
cooking. I'm working on the assumption that if that is the case, dishes
and
cups, and bowls made the same way can be used for eating. If there's a
difference, that is, if this assumption is not so, I'd appreciate
someone's
letting me know.
Martin
Santiago de Puriscal, Costa Rica
Where the new house we're building is now two months behind schedule and
I've had to fire the architect and builder. Now we have a new crew and
think
we'll be living in the house, which is simply lovely -- log and stone --
in
three more weeks. Which, in turn means, that I'll finally be able to use
my
new studio and continue making my ugly little vessels. Really difficult
to
wait even these few weeks. It's been almost a year since the last time I
muddied my hands.
________________________________________________________________________
______
Send postings to clayart@lsv.ceramics.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
melpots@pclink.com.
Snail Scott on sun 18 jul 04
At 01:42 PM 7/18/04 -0500, Ron wrote:
>Probably best to check and see exactly what is in the clay you are using -
>many of the clays we use have stuff in them that can be a risk factor.
>
>I wonder if he is using Barium Carb to stop scumming for instance?
Surely the less-than-1% of barium typically
used to prevent scumming is unlikely to be
a health risk, even with undervitrified clay
used for regular food consumption?
-Snail
Ivor and Olive Lewis on sun 18 jul 04
Dear Martin,
I would not wish to use unglazed earthenware as table ware.
Best regards,
Ivor
Craig Dunn Clark on sun 18 jul 04
Martin, I have used Red Art, as well as Gold Art, as part of a stoneware
body that we used to mix and pug up in school. I am not certain but if you
are going to use it for a low fire body that you want to use for food
service purposes then it probably a good idea to check with the folks at
Cedar Heights and ask them at what temperature Red Art will become vitreous.
We used it in the following proportions in our body.......100lbs
Hawthorn Bond (a Missouri Fire CLay), 50lbs Old Mine #4 Ball Clay, 50lbs Red
Art, a little grog, about 10% Custer Spar (if we were firing to cone 10) and
a coupla handfuls of Bentonite. Mixed everything up in a Soldner Mixer and
pugged/de-aired in a Venco mill.
At the very least go ahead and do an absorption test before using
whatever clay body you decide upon for table service.
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From: "Lee Love"
To:
Sent: Saturday, July 17, 2004 7:51 PM
Subject: Re: Confused about low fire - food safe
> Martin Rice wrote:
>
> >fire/food safe pottery. It sounds to me that the consensus is that yes,
> >indeed, red clay fired to ^04, with or without terra sig can be used for
> >cooking.
> >
>
> Martin, if you are only using clay for your pots, then it all
> depends upon the clay.
>
> I think the clay at the web example is Cedar Heights Red Art.
>
>
>
> --
> Lee in Mashiko, Japan http://mashiko.org
> http://www.livejournal.com/users/togeika/ WEB LOG
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.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
melpots@pclink.com.
Lee Love on sun 18 jul 04
Martin Rice wrote:
>fire/food safe pottery. It sounds to me that the consensus is that yes,
>indeed, red clay fired to ^04, with or without terra sig can be used for
>cooking.
>
Martin, if you are only using clay for your pots, then it all
depends upon the clay.
I think the clay at the web example is Cedar Heights Red Art.
--
Lee in Mashiko, Japan http://mashiko.org
http://www.livejournal.com/users/togeika/ WEB LOG
Ron Roy on sun 18 jul 04
Probably best to check and see exactly what is in the clay you are using -
many of the clays we use have stuff in them that can be a risk factor.
I wonder if he is using Barium Carb to stop scumming for instance?
RR
>Martin Rice wrote:
>
>>What I didn't get from the discussion is whether any of the respondents were
>>reacting to this site and the claims there. I'd really love to know if
>>anyone has an opinion about whether this type of pot could be food safe.
>>
>>
>
>Martin, He uses "safe" materials in the making of this work. It is
>all RedArt. I would confidently bake pies in his pie plates as I
>would confidently drink tea from a Linda Arbuckle majolica teacup.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
John Hesselberth on mon 19 jul 04
On Sunday, July 18, 2004, at 11:45 PM, Snail Scott wrote:
> Surely the less-than-1% of barium typically
> used to prevent scumming is unlikely to be
> a health risk, even with undervitrified clay
> used for regular food consumption?
>
> -Snail
Hi Snail,
That's an interesting question. I hadn't really thought about it so I
went to my Sax Handbook (Dangerous Properties of Industrial Materials).
Sax says the LD50 (the dose that is lethal for 50% of those getting it
into their bodies by means other than inhalation) for barium oxide is
50 mg/kg. So an 80 kg (176 lb) person would have to ingest 4000 mg or 4
grams. A 3 lb pot containing 1% BaO contains 13.6 grams BaO--more than
enough. So it would all depend on how tied up that barium is and what
its form it--is it easily leachable/extractable or not? Has it
converted to the oxide (from the carbonate which we usually use) or
not--the carbonate being somewhat less toxic--see below?
I obviously don't know the answers--maybe someone else does.
What I do know is that barium carbonate is a material that should be
handled with great care--if you choose to have it in your studio. It is
not as toxic as the oxide--probably because it is less soluble--but
still has an LD50 of 400 and 630 mg/kg for dogs and rats respectively
and, of course, will make you sick at concentration well below those.
Regards,
John
John Hesselberth
http://www.frogpondpottery.com
http://www.masteringglazes.com
Lee Love on mon 19 jul 04
Ron Roy wrote:
>Probably best to check and see exactly what is in the clay you are using -
>many of the clays we use have stuff in them that can be a risk factor.
>
>I wonder if he is using Barium Carb to stop scumming for instance?
>
>
>
He says his clay is just clay, and his terra sig is: 20% red clay, 80%
distilled water and .5% Calgon
Check out his process:
http://www.hesspottery.com/nPrcss.htm
If you would like to ask Tom directly, write him at:
info@hesspottery.com
--
in Mashiko, Japan http://mashiko.org
http://www.livejournal.com/users/togeika/ WEB LOG
Ron Roy on wed 21 jul 04
Hi Snail,
Tuckers does testing on all the RedArt that comes in - quite a lot over the
years - and there is some scumming - sometimes quite obvious - so I suspect
this potter may be using barium to stop the scumming.
Typical amounts would be from 2 to 3% of the dry weight.
What makes this tricky - if you don't test each lot for scumming - and use
the same amount of barium each time - if there are less salts available to
react with the barium it does not combine and is present in a more soluable
form.
I don't know if it is a danger - but remember that the effect of poison has
a lot to do with body weight - pregnant mothers should not be injesting any
Barium at all for instance.
I am just using this as an example - there are other toxins that come with
clays.
What I am trying to point out is - once we sell the pot we don't have any
control on how the ware will be used.
In this case the clay is underfired and that can result in problems with
some types of use. Because it is not glazed it will be more open to attack
when used with acidic food - especially if it is used for storing and/or
cooking acidic food.
I think we should at least be thinking about this sort of thing if we want
to make better pots that will suit the purposes they are used for.
RR
>At 01:42 PM 7/18/04 -0500, Ron wrote:
>>Probably best to check and see exactly what is in the clay you are using -
>>many of the clays we use have stuff in them that can be a risk factor.
>>
>>I wonder if he is using Barium Carb to stop scumming for instance?
>
>
>Surely the less-than-1% of barium typically
>used to prevent scumming is unlikely to be
>a health risk, even with undervitrified clay
>used for regular food consumption?
>
> -Snail
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.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 melpots@pclink.com.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Lee Love on wed 21 jul 04
Ron Roy ( ronroy@CA.INTER.NET ) wrote:
>Hi Snail,
>
>Tuckers does testing on all the RedArt that comes in - quite a lot over the
>years - and there is some scumming - sometimes quite obvious - so I suspect
>this potter may be using barium to stop the scumming.
>
You might ask Tom Hess . I wouldn't spread gossip about
someone's work unless I knew for sure.
Write here: info@hesspottery.com
Webpage:
http://www.hesspottery.com/nPrcss.htm
Keep and open mind. Maybe we can learn something: Maybe Calgon
stops scumming? Or terra sig? Floating small particles might get
rid of the scumming problem
--
Lee in Mashiko, Japan http://mashiko.org
http://www.livejournal.com/users/togeika/ WEB LOG
Anne Webb on wed 21 jul 04
From Lee Love's post on Wed, 21 Jul 2004 19:02:34:
>Ron Roy wrote:
>>Hi Snail,
>>
>>Tuckers does testing on all the RedArt that comes in - quite a lot over
>>the years - and there is some scumming - sometimes quite obvious - so I
>>suspect this potter may be using barium to stop the scumming.
>>
>
>You might ask Tom Hess . I wouldn't spread gossip about
>someone's work unless I knew for sure.
> Keep and open mind. Maybe we can learn something: Maybe Calgon
>stops scumming? Or terra sig? Floating small particles might get rid
>of the scumming problem
Hi Lee..
Just a sec, Lee, but there needs to be some clarification here.
Don't take this the wrong way, but in Ron's defense, if you had taken the
time to read further than the first paragraph in his post, you would realize
that you had taken things completely out of context.
Ron was NOT assuming that barium was in fact the de-scumming agent being
used on that guy's work; he suspected it based on his experience, but never
said, in fact, that it was. What he said, and i quote, is:
"I wonder if he is using Barium Carb to stop scumming for instance?" ..but
I guess you missed that.
the rest is posted below. I have also pasted the part of ron's last email
that you neglected to include.
"I wouldn't spread gossip about someone's work unless I knew for sure.."
does that mean you *would* gossip about someone's work if you *did* know for
sure? ...Please.
>At 01:42 PM 7/18/04 -0500, Ron wrote:
>>Probably best to check and see exactly what is in the clay you are using
>>- many of the clays we use have stuff in them that can be a risk factor.
>>
>>I wonder if he is using Barium Carb to stop scumming for instance?
>
>
>Surely the less-than-1% of barium typically used to prevent scumming is
>unlikely to be a health risk, even with undervitrified clay used for
>regular food consumption?
>
> -Snail
The other part of Ron's email:
> I am just using this (barium) as an example - there are other
>toxins that come with clays. What I am trying to point out is - once we
>sell the pot we don't have any control on how the ware will be used. In
>this case the clay is underfired and that can result in problems with some
>types of use. Because it is not glazed it will be more open to attack when
>used with acidic food - especially if it is used for storing and/or cooking
>acidic food. I think we should at least be thinking about this sort of
>thing if we want to make better pots that will suit the purposes they are
>used for.
I hope this was a help.
Anne
_________________________________________________________________
Discover the best of the best at MSN Luxury Living. http://lexus.msn.com/
Lee Love on thu 22 jul 04
Anne Webb wrote:
Ron wrote:
>>> so I suspect this potter may be using barium to stop the scumming.
>>>
"Suspicions" can be laid to rest. From the "horses mouth":
Thom Hess wrote:
>Greetings,
>I mix my RedArt with a lot of water (15gal. water/ 50 lbs. clay), let the
>clay settle several weeks and siphon off the water.
>This process removes much of the soluble salts and makes the clay more
>plastic by thoroughly wetting the clay particles. I do not use barium or
>plasticizers in my clay preparation.
>Sincerely,
>Tom Hess
>
You can write Tom directly here:
info@hesspottery.com
Or see his work at his web page Webpage:
http://www.hesspottery.com
--
Lee in Mashiko, Japan http://mashiko.org
http://www.livejournal.com/users/togeika/ WEB LOG
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