Deborah Redfern on sat 17 jan 98
This query is in response to the recipe Camille Culp shared, Metalic Glossy Bla
"The Metallic Glossy Black is very black alone. It's a beautiful midnight blue
lighter blue breaks over other glazes. It's one of the most interesting at this
that I've used," She asked if the recipe was food safe and I didn't hear any
reponses. I tried the recipe and it is extremely beautiful, Camille, I agree.
want to use it on my dinnerware. Does this recipe raise any warning flags?
Metallic Glossy Black Oxidation Cone 6 - 8 (I use 7)
Feldspar 71.5
Whiting 4.9
Gerst B. 9.2
Kaolin 4.4
Copper C 3.0
Mang D. 3.0
Cobalt C. 1.5
So here are my questions:
1) is this food safe?
2) If it isn't food safe, I have been playing around with using this glaze as an
accent on the rim, and using a clear transparent on the inside. Not all that ea
task I've discovered. Apart from brushing it on, or airbrushing (I've tried bot
does anyone have any ideas for doing this neatly and efficiently?
3) if the glaze becomes a lighter breaking blue on top of another glaze, does th
mean there is a lighter coat where they overlap, and would this make it more foo
safe? I could glaze just the inside of the bowl with clear transparent and then
the whole piece in the black. I may try that anyway, even if the the recipe is
okay. It sounds like it might be very striking.
Any help would be greatly appreciated.
Deborah
redfern.d@thezone.net
//Two roads diverged in a wood, and I - I took the one less traveled by,
and that has made all the difference.// - Robert Frost -
Craig Martell on sun 18 jan 98
At 09:35 AM 1/17/98 EST, Deborah Redfern wrote:
>----------------------------Original message----------------------------
>This query is in response to the recipe Camille Culp shared, Metalic
Glossy Bla
>"The Metallic Glossy Black is very black alone. It's a beautiful midnight blue
>lighter blue breaks over other glazes. It's one of the most interesting at
this
>that I've used," She asked if the recipe was food safe and I didn't hear any
>reponses. I tried the recipe and it is extremely beautiful, Camille, I agree.
>want to use it on my dinnerware. Does this recipe raise any warning flags?
>
>Metallic Glossy Black Oxidation Cone 6 - 8 (I use 7)
>
>Feldspar 71.5
>Whiting 4.9
>Gerst B. 9.2
>Kaolin 4.4
>Copper C 3.0
>Mang D. 3.0
>Cobalt C. 1.5
Hello Deborah:
This glaze doesn't call for a particular type of feldspar, so I calculated
it with both potash and soda to see what would happen. In both instances,
the glaze had sufficient silica to make it a safe base without the added
colorants. There is an oversupply of alumina which may retard the melt and
make this glaze matt. Is that happening? It also has a very high
expansion, due to an oversupply of potassium and sodium. This will probably
make the glaze craze on most bodies which will improve the chances of
leaching. It looks like this glaze could stand a bit of tweaking before it
would be safe for dinnerware and even after the adjustments, I would have it
tested for leaching before I put any ware on the market.
I don't know if using it with a clear transparent would make the glaze safe
for food use or not. With the high expansion, the black glaze would
probably make the clear craze if it doesn't already.
If you would like some help adjusting this glaze, I would be glad to offer
some suggestions and or formulas.
regards, Craig Martell-Oregon
Tony Hansen on mon 19 jan 98
> I tried the recipe and it is extremely beautiful, Camille, I agree.
> want to use it on my dinnerware. Does this recipe raise any warning flags?
> Metallic Glossy Black Oxidation Cone 6 - 8 (I use 7)
Feldspar 71.50 CaO 0.39*
Whiting 4.90 K2O 0.38*
Gerst B 9.20 Na2O 0.23*
Kaolin 4.40 Al2O3 0.68
======== B2O3 0.34
90.00 SiO2 4.16
Fe2O3 0.00
Cost/kg 17.78
Si:Al 6.16
SiB:Al 6.65
Expan 8.31
Did you put some vinegar in a container of this glaze overnight.
The presence of copper means this is likely to be leachable.
This glaze has a very high expansion because of the high feldspar,
it will craze on most clay bodies.
--
-------
T o n y H a n s e n thansen@digitalfire.com
Get INSIGHT, Magic of Fire at http://digitalfire.com
Ron Roy on tue 20 jan 98
Hi Deborah,
1) is this food safe?
I don't know - there is plenty of alumina and silica - but it is
oversupplied with KNaO and way more copper, manganese and copper than is
recommended for a food safe glaze. I don't know what would come out - or
under what circumstances - and how much would be a problem - the only way
to find the answers would be to have the glaze tested for leaching of the
copper, manganese and cobalt.
I would not want to eat off it - or to be more particular - certainly not
want to eat food that was stored or cooked on it.
Putting another food safe glaze over it would help a lot in terms of
reducing the leaching - glazing the outside first with the black and then
the inside with a clear safe glaze would seem to offer decorative
possibilities - especially if you use some wax decoration on top of the
black so that when you dipped the rim you could control the line where the
transparent and black met.
>----------------------------Original message----------------------------
>This query is in response to the recipe Camille Culp shared, Metalic
>Glossy Bla
>"The Metallic Glossy Black is very black alone. It's a beautiful midnight blue
>lighter blue breaks over other glazes. It's one of the most interesting
>at this
>that I've used," She asked if the recipe was food safe and I didn't hear any
>reponses. I tried the recipe and it is extremely beautiful, Camille, I agree.
>want to use it on my dinnerware. Does this recipe raise any warning flags?
>
>Metallic Glossy Black Oxidation Cone 6 - 8 (I use 7)
>
>Feldspar 71.5
>Whiting 4.9
>Gerst B. 9.2
>Kaolin 4.4
>Copper C 3.0
>Mang D. 3.0
>Cobalt C. 1.5
>
>
>So here are my questions:
>
>1) is this food safe?
>2) If it isn't food safe, I have been playing around with using this glaze
>as an
>accent on the rim, and using a clear transparent on the inside. Not all
>that ea
>task I've discovered. Apart from brushing it on, or airbrushing (I've
>tried bot
>does anyone have any ideas for doing this neatly and efficiently?
>3) if the glaze becomes a lighter breaking blue on top of another glaze,
>does th
>mean there is a lighter coat where they overlap, and would this make it
>more foo
>safe? I could glaze just the inside of the bowl with clear transparent
>and then
>the whole piece in the black. I may try that anyway, even if the the
>recipe is
>okay. It sounds like it might be very striking.
>
> Any help would be greatly appreciated.
>
>Deborah
>redfern.d@thezone.net
>//Two roads diverged in a wood, and I - I took the one less traveled by,
> and that has made all the difference.// - Robert Frost -
Ron Roy
93 Pegasus Trail
Scarborough,Canada
M1G 3N8
Evenings, call 416 439 2621
Fax, 416 438 7849
Studio: 416-752-7862.
Email ronroy@astral.magic.ca
Home page http://digitalfire.com/education/people/ronroy.htm
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