Paul Taylor on wed 7 mar 01
Dear Andie
To answer a few
> 1) In a book I've been reading about a particular potter, I notice that
> his glaze recipes for his functional wares are predominantly wood ash
> glazes, some only woodash and slip, fired to cone 8 in various
> atmospheres. I was under the impression that the pinholes and runny,
> sometimes crazing textures that ash glazes tend to produce were not
> suitable for food surfaces. Can someone enlighten me?
Wood ash glazes can be made as food safe as any at cone *8 no poisonous
substances need be used. If the surface is silk matt you have to scrub them
a bit more if you are a worried. If they are runny in rivers they will need
a lot of scrubbing to get clean.
. There is an argument that the detergents used in our obsession for
cleanliness can cause more problems for health than the occasional tummy
upset. I have a friend who only uses very hot water to wash up . He is a
microbiologist.
Some ash glazes can be a little soft: giving the pot a tap will tell you
how soft - the clearer the ringing sound the tougher the glaze.
> 2) In the same book, the layering of glazes made me wonder: if I have
> two stable, food safe (let's say store-bought) glazes, and I layer them
> on a food surface, are they likely to still be food safe?
No problem with layering . But I expect someone can think up an odd
coincidence where I could be wrong. Without paranoia you have no Insurance
industry and civilization as we know it disappears.
>
> 3) If I am firing a clay body to it's highest temp, so it is completely
> vitrified, would an unglazed surface be safe for food surfaces? If not,
> what about the ladles and such that I often see with the underside of
> the dipper unglazed?
Most stonewares that are oven safe absorb a small percentage of water
along with the germs the water carries. I think or domestic purposes people
can deal with that . But for restaurants you are asking for trouble.
> Thanks in advance for furthering my education -
>
> : ) Andie in MD
> Where the snow is falling, but gently.
> PS: new photos up on the mug exchange page!!
>
Andie Carpenter on wed 7 mar 01
Let me preface this by saying that I did do my homework, and didn't find
answers to these in the archives or in Hamer's, Chappell's, or Rhodes.
1) In a book I've been reading about a particular potter, I notice that
his glaze recipes for his functional wares are predominantly wood ash
glazes, some only woodash and slip, fired to cone 8 in various
atmospheres. I was under the impression that the pinholes and runny,
sometimes crazing textures that ash glazes tend to produce were not
suitable for food surfaces. Can someone enlighten me?
2) In the same book, the layering of glazes made me wonder: if I have
two stable, food safe (let's say store-bought) glazes, and I layer them
on a food surface, are they likely to still be food safe?
3) If I am firing a claybody to it's highest temp, so it is completely
vitrified, would an unglazed surface be safe for food surfaces? If not,
what about the ladles and such that I often see with the underside of
the dipper unglazed?
Thanks in advance for furthering my education -
: ) Andie in MD
Where the snow is falling, but gently.
PS: new photos up on the mug exchange page!!
John Hesselberth on wed 7 mar 01
Andie Carpenter wrote:
>2) In the same book, the layering of glazes made me wonder: if I have
>two stable, food safe (let's say store-bought) glazes, and I layer them
>on a food surface, are they likely to still be food safe?
Probably. If the understanding I am gaining doesn't have a great big
hole in it someplace, I believe mixing, blending, layering two stable
glazes will yield a stable glaze.
Be aware though that different "stores" have different views of the term
"food safe". I am finding there is no agreed on definition of that
terms. That is why I use the term "stable" or "durable" rather than
"food safe". I will show some commercial "food safe" glazes at NCECA that
are just as bad as the 2 I included in the letter to the editor of the
March issue of CM.
In other words, just because a glaze manufacturer says it is food safe
doesn't mean it won't leach terribly. Some glaze manufacturers have much
higher standards and/or are much more competent in formulating glazes
than others.
Regards, John
"The life so short, the craft so long to learn." Chaucer's translation of
Hippocrates, 5th cent. B.C.
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