John Hesselberth on wed 19 apr 00
Cerere@aol.com wrote:
>----------------------------Original message----------------------------
>The following glaze was posted as FOOD SAFE
>Ron Roy cone 6 black #1
>F4 Feldspar...21.00
>Whiting.....6.00
>Talc.......3.00
>Frit 3134....26.00
>EPK Kaolin......17.00
>Silica....27.00
>Iron Oxide Red......9.00
>Cobalt Carb.....1.00
>
>Can a glaze be food safe with cobalt? Maybe the base is food safe, but then
>it's not black!
>
>Thanks to anyone who can answer my question.
>Toni
Hi Toni,
RR Black is an extremely stable glaze. I have tested it for leaching of
cobalt and found that virtually none comes out--only 0.076 mg/l. That is
barely above the detectable limit. Some of the other variants of this
glaze I tested leached less than the detectable limit. It is the most
stable black glaze I have seen. Please remember that is with my
ingredients in my kiln and with my firing conditions. To be sure you
should test it with your ingredients, in your kiln and with your firing
conditions. For instructions on having your glazes tested at minimal
cost please visit my web site at:
http://www.frogpondpottery.com/glazetest.html
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.
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