Diane Woloshyn on wed 29 sep 99
Finally have my test results from Alfred after 3 months. Their machines
broke and it took a month to get parts.
When I called, they said the tests were all very low, but they had no guide
lines for lithium. The following are the formulas, results, and my comments
or questions.
GIBBY'S WILD ROSE/KAKI ^6
Lithium Carb 10.5
Bone Ash 10.5
Neph Sy 61.5
Tile 6 Kaolin 17.5 (I use EPK)
Add:
Red Iron Oxide 10.5 %
IRON RED/ORANGE (Kaki is Japanese for persimmon)
Lithium was 7.32 MG/L
This seems high to me and I wouldn't use it as a food safe glaze.
FALLS CREEK SHINO ^6
Albany slip 56.07 561
Gerstley Borate 18.69 187
Soda feldspar 9.35 93.5
Silica 9.35 93.5
Lithium carbonate 6.54 65.5
Superpax 9.35 93.5
Tin oxide 4.67 46.7
Lithium was below detectable limits.
Hooray, I use this a lot.
RON ROY'S BLACK # 2 WITH MASON STAIN
Soda Feldspar 21
Whiting 6
Talc 3
Frit 3134 26
EPK 17
Flint 27
Bentonite 2
Red Iron Oxide 9
Cobalt Carb 1
Black Mason Stain 1
Cobalt was 0.l0 MG/L
Manganese was 0.50 MG/L
The manganese is above the acceptable limits for water, which is 0.030. This
would not be acceptable as food safe for anything I would sell.
SAFFIRE BLUE
EPK 25.5
Frit 3134 42.6
Custer feldspar 25.5
Silica 15.0
Rutile 4.3
Cobalt Oxide 2.13
Cobalt was 0.13 MG/L
No limits for water identified in the US. Maybe Monona has a recommendation
on this.
FLOATING GREEN
Neph Syenite 30
Gerstley 21
Whiting 8
EPK 10
Flint 31
Chrome oxide 2
Cobalt oxide 1
Cobalt was less than the detectable limit.
Chrome was 0.05 MG/L
The cobalt was very low and he said the chrome was also. But this is not a
very well behaved glaze, because all the Gerstley. I have tried another
based on RR Black # 2 and have sent it for testing.
Any comments or help anyone can further offer is appreciated. And my special
thanks to Ron Roy for his original black formula.
Diane Florida Bird Lady
Diane Woloshyn on thu 30 sep 99
Hi Sandy,
Yes, all oxidation glazes. Sorry I didn't include that.
Diane Florida Bird Lady
Craig Martell on fri 1 oct 99
Diane, the bird lady, remarked:
>----------------------------Original message----------------------------
>Finally have my test results from Alfred after 3 months. Their machines
>broke and it took a month to get parts.
>
>
>RON ROY'S BLACK # 2 WITH MASON STAIN
>
>Soda Feldspar 21
>Whiting 6
>Talc 3
>Frit 3134 26
>EPK 17
>Flint 27
>Bentonite 2
>Red Iron Oxide 9
>Cobalt Carb 1
>Black Mason Stain 1
>
>Cobalt was 0.l0 MG/L
>Manganese was 0.50 MG/L
>
>The manganese is above the acceptable limits for water, which is 0.030. This
>would not be acceptable as food safe for anything I would sell.
Hey Diane:
Remove the 1% black mason stain and you won't have to be concerned about
the MnO2 thing. I believe that Ron's original glaze only had cobalt and
iron as colorants. You could also do some tests with added silica if you
want to keep the mason stain.
regards, Craig Martell in Oregon
John Hesselberth on fri 1 oct 99
Diane Woloshyn wrote:
>
>The manganese is above the acceptable limits for water, which is 0.030
Hi Diane,
Thanks very much for publishing your glaze testing results. They will be
useful additions to the data I am collecting.
Where, though, did you find limits for manganese in water? I was not
aware that there were any in the U.S. I remember reading someplace that
Canada had proposed a limit of 2.0 mg/l for manganese but it was not
adopted yet. Can you remember your source? I'd sure like to have it.
Manganese via ingestion is not normally considered terribly toxic. It is
the fumes you don't want to breathe.
John Hesselberth
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: john@frogpondpottery.com web site: http://www.frogpondpottery.com
"It is time for potters to claim their proper field. Pottery in its pure
form relies neither on sculptural additions nor on pictorial decorations.
but on the counterpoint of form, design, colour, texture and the quality
of the material, all directed to a function." Michael Cardew in "Pioneer
Pottery"
Vicki Ferris on fri 1 oct 99
Diane,
Thank you for posting the results of your glaze tests! That should help us
all. Just think, if each of us would have "one" of our glazes tested and post
to the list, we all would be so much smarter and safer. Thanks for sharing
your information. By the way, are all the recipies ^6 oxidation?
Vicki in Cool, CA
Russel Fouts on sat 2 oct 99
>> Thank you for posting the results of your glaze tests! That should help us al
We're thankful to the people who are posting these results ... AS
GUIDLINES.
But I think it is a mistake to assume that if one person's glaze tests
food safe that it will be also safe with your water, your application
method, on your claybody, in your atmosphere, your firing cycle, etc,
etc.
Russel Fouts
Mes Potes et Mes Pots
Brussels, Belgium
Ron Roy on mon 4 oct 99
Hi Diane,
John Hesselberth found the original with 1% cobalt carb not black enough -
others found it OK as is.
John tried it at 1.5 and 2% Cobalt and it was black enough for him then -
had it tested and it released even less cobalt ( below detectable limits of
0.05mg/L than the original. I don't recommend using a black stain - it will
either have manganese or chrome or both - and just not necessary.
I am curious about the difference in your results - Cobalt at 0.10 - John
Used the Custer variation. Any comments on this John?
>----------------------------Original message----------------------------
>Finally have my test results from Alfred after 3 months. Their machines
>broke and it took a month to get parts.
>
>
>RON ROY'S BLACK # 2 WITH MASON STAIN
>
>Soda Feldspar 21
>Whiting 6
>Talc 3
>Frit 3134 26
>EPK 17
>Flint 27
>Bentonite 2
>Red Iron Oxide 9
>Cobalt Carb 1
>Black Mason Stain 1
>
>Cobalt was 0.l0 MG/L
>Manganese was 0.50 MG/L
>
>The manganese is above the acceptable limits for water, which is 0.030. This
>would not be acceptable as food safe for anything I would sell.
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
John Hesselberth on tue 5 oct 99
Ron Roy wrote:
>I am curious about the difference in your results - Cobalt at 0.10 - John
>Used the Custer variation. Any comments on this John?
The difference in our results is probably insignificant and within normal
experimental error. After all it was a slightly different composition
mixed by a different potter put on a different clay and fired in a
different kiln. And then there is the fact that we used different cups
undoubtedly made to different dimensions so the surface area exposed to
the measured amount of acid was different. The cobalt release could also
be affected by the presence of manganese and chrome in the stain. Even
within my own results the 1.0% cobalt number was higher than the 2.0%
number. There's just lots of opportunity for experimental error in all
this. All in all, I am pleased that they are as close as they are.
John Hesselberth
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: john@frogpondpottery.com web site: http://www.frogpondpottery.com
"It is time for potters to claim their proper field. Pottery in its pure
form relies neither on sculptural additions nor on pictorial decorations.
but on the counterpoint of form, design, colour, texture and the quality
of the material, all directed to a function." Michael Cardew in "Pioneer
Pottery"
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