Susan Ford on tue 2 oct 01
I'm going to be doing some experimenting with
Mason (and other) stains in slips to decorate my
pots. I notice that they are available in a variety of
colors, and use some colorants that I might not be
good for functional use with food.
My question I suppose is how safe are the stains for
use in food containers? I make a LOT of soup bowls
(my favorite way to eat..), chili bowls, pasta bowls,
bowls, bowls, bowls, and I'd like to decorate the
insides of these bowls with slips.
How safe are some of these ingredients under a
good strong clear coat of glaze? Copper, chrome,
tin, cobalt, etc.
Susan
---
Susan K. Ford
Norman, Oklahoma
http://www.clueless.norman.ok.us/sf/rerhome.htm
The weakest ink lasts longer
than the strongest memory.
-- Confucious
Craig Martell on tue 2 oct 01
Susan asked:
>My question I suppose is how safe are the stains for
>use in food containers?
>How safe are some of these ingredients under a
>good strong clear coat of glaze?
Hi:
As always, it depends on the amount of stain, whether or not it's toxic,
how it's fired, what kind of glaze one uses etc.
It's absolutely impossible to tell if a glaze is going to be durable and
food safe without at least looking at the molecular formula. Not the
recipe, but the formula, which gives us a look at what's in the fired
glaze. Even when we can look at the formula, we are only able to predict
the level of durability. To get an answer to your question, you will need
to have the glaze or glazes subjected to an acid leach test by an
accredited lab.
That's probably not the answer you wanted, but that's the answer to the
question. If you give someone the recipe to your glaze or glazes we could
run them thru analysis and tell you if they "might" be OK.
regards, Craig Martell in Oregon
John Hesselberth on tue 2 oct 01
on 10/2/01 2:33 PM, Susan Ford at susanford@MUTT.SLACKFORD.COM wrote:
> My question I suppose is how safe are the stains for
> use in food containers? I make a LOT of soup bowls
> (my favorite way to eat..), chili bowls, pasta bowls,
> bowls, bowls, bowls, and I'd like to decorate the
> insides of these bowls with slips.
>
> How safe are some of these ingredients under a
> good strong clear coat of glaze? Copper, chrome,
> tin, cobalt, etc.
Hi Susan,
Unfortunately, no one knows the answers to your questions. There is a
limited amount of evidence that a good clear glaze can reduce the leaching,
but you will have to test each combination to be sure. Copper is the most
questionable, but fortunately for you, Mason doesn't use copper in any of
their stains.
Regards,
John
Web site: http://www.frogpondpottery.com Email: john@frogpondpottery.com
"The life so short, the craft so long to learn." Chaucer's translation of
Hippocrates, 5th cent. B.C.
Martin Howard on wed 3 oct 01
The stains sold in the UK are often accompanied by a statement that they are
food safe IF covered with such and such clear glaze.
That seems to answer your hesitation about their use, Susan.
I use them in a variety of colours in slip, and then clear glaze them OR
cover with a coloured glaze which produces some very interesting
combinations. Now testing each slip under each glaze to see just what
combinations are available.
What I cannot get is a statement as to just what each stain contains. If we
had that we could add other oxides to the stains and avoid those
combinations which we know do not work for us.
The same idea can surely be used with any suspect mineral combination. Just
put it in the slip, decorate as much as you like, then clear glaze with a
food safe glaze.
Just make sure it fits body and slip well.
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
This web-site is about to be updated.
miriam shelomith on wed 3 oct 01
If the stains that you are using are Mason stains, call them directly. Have
found, through the years, that the folks there are most helpfull, willing
and knowledgeable.
I fire to cone 6 and use stains in slip under a clear glaze for the billions
of bowls and other food items that I have made over the past 25 years.
pottermim
>From: Craig Martell
>Reply-To: Ceramic Arts Discussion List
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Re: Mason Stains in slips
>Date: Tue, 2 Oct 2001 16:24:57 -0700
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>Susan asked:
>>My question I suppose is how safe are the stains for
>>use in food containers?
>>How safe are some of these ingredients under a
>>good strong clear coat of glaze?
>
>Hi:
>
>As always, it depends on the amount of stain, whether or not it's toxic,
>how it's fired, what kind of glaze one uses etc.
>
>It's absolutely impossible to tell if a glaze is going to be durable and
>food safe without at least looking at the molecular formula. Not the
>recipe, but the formula, which gives us a look at what's in the fired
>glaze. Even when we can look at the formula, we are only able to predict
>the level of durability. To get an answer to your question, you will need
>to have the glaze or glazes subjected to an acid leach test by an
>accredited lab.
>
>That's probably not the answer you wanted, but that's the answer to the
>question. If you give someone the recipe to your glaze or glazes we could
>run them thru analysis and tell you if they "might" be OK.
>
>regards, Craig Martell in Oregon
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
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>
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>melpots@pclink.com.
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