Candice Roeder on fri 28 jul 00
Hi,
I have a question on the food safety of a glaze. The glaze is Basic 6
clear from the Digital Fire website. I know it is a balanced glaze, and
is a safe one to use, but I've added 8% ceramic stain and I wondered if
the inclusion of the stain makes it unsafe. Nice glaze to work with, by
the way.
Here is what I'm using:
20 EPK
20 Flint
20 Wollastonite
20 Frit 3134
20 Custer Feldspar
8 Mason Stain 6600 Black
Is there an amount of stain or oxide that would make this glaze an
unsafe one to use? I'm wondering about limits, since I'm doing color
tests right now.
Thanks for your help.
Candice
John Hesselberth on fri 28 jul 00
Candice Roeder wrote:
>
>Is there an amount of stain or oxide that would make this glaze an
>unsafe one to use? I'm wondering about limits, since I'm doing color
>tests right now.
Hi Candice,
Sorry, but the only way to know is to have it tested. There are
instructions on how to do this economically on my web site at:
http://www.frogpondpottery.com/glazetest.html
There is also a perspective on how you might interpret the results on
another page on my site. If you need any specific help on what to test
for I'd be glad to offer an opinion.
John Hesselberth
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: john@frogpondpottery.com web site: http://www.frogpondpottery.com
"Pots, like other forms of art, are human expressions: pleasure, pain or
indifference before them depends upon their natures, and their natures
are inevitably projections of the minds of their creators." Bernard
Leach, A Potter's Book.
John Baymore on sat 29 jul 00
I have a question on the food safety of a glaze. The glaze is Basic 6
clear from the Digital Fire website. I know it is a balanced glaze, and
is a safe one to use, but I've added 8% ceramic stain and I wondered if
the inclusion of the stain makes it unsafe. ............................=
..
Is there an amount of stain or oxide that would make this glaze an
unsafe one to use? =
Candice,
Tony Hansen certainly knows what he is doing . So a glaze from the DF=
site certainly will "start out" as stated on the site.
When you "add" something to a glaze recipe, which alters the fired chemic=
al
formula, you have changed the glass. So the other properties it exhibits=
,
along with the color in this case, MAY have also changed. Only way to kn=
ow
for sure is to have it tested.
You need to know what to test FOR. I don't have the charts for Mason
Stains near the computer.... but I would guess that the black contains a
few potentially toxic colorants. Mason can tell you generally WHAT is in=
the stain.... not the specific proportions... just that something is
present. You should check this to see if there is a reason for concern. =
At an 8 percent inclusion...the stain is a significant portion of the gla=
ze
batch.
If a base glaze has few particularly toxic oxides present and then then y=
ou
added something like say.......more calcium carbonate........ increasing
the CaO proportion in the melt, you might not have to worry too much
because the material you have added is relatively innocous.... and the re=
st
of the glaze is too. So if it changes the leaching / hardness / durabili=
ty
of the glass..... it is not a significant "hazard" to the end user (in th=
e
recently proposed "Nutrimugs" line... this would be the antacid mug ).=
=
If you are concerned about durability however........ then you might want=
ot test some other properties .
Best,
..............................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752 (s)
800-900-1110 (s)
JBaymore@compuserve.com
John.Baymore@GSD-CO.com
"Earth, Water, and Fire Noborigama Woodfiring Workshop August 18-27,
2000"
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