Fay & Ralph Loewenthal on thu 29 apr 99
Randall here is the recipe from James Chappell's book. I
have made it and it came out perfect except that I did not
grind it fine enough. I have typed it out verbatim from his
book. I would strongly suggest that you buy or borrow a copy.
Whiting 23.9
Calcium Sulfate 6.5
Fluospar 4.5
Silica 20.8
Tin Oxide 43.7
Zinc Oxide 1.0
Potassium Dichromate 1.6
Mixing: Weigh out the ingredients in grams or pounds. Dry
mix by hand or in a ball mill for five minutes, then place in a
crucible and calcine to cone 8. After calcining, place in a ball
mill and dry grind for four to five hours. Do not undergrind
any stain as most stains of this type must be finely ground to
give true colours. After grinding mix the stain with water to
the consistency of milk and sieve through a 200 mesh screen.
It is now ready to use for spraying or brushing an entire pot.
It needs to be the consistency of condensed milk for
underglaze painting. Hope this helps Ralph in PE SA.
Randall Moody on sat 1 may 99
Thank you! I had just about given up on the whole thing and bought the Mason
stain (still an option.) This is the recipe that I have. I am still
wondering what the colorant is. I deep into the end of semester rush so it
may be next semester before I get some made and tested, but I will post the
results on ClayArt. I have found that Potassium Dichromate is bad...very
bad. But I figure in such a small amount it shouldn't be too bad.
Again thanks to you and to all who were trying to help me.
> Whiting 23.9
> Calcium Sulfate 6.5
> Fluospar 4.5
> Silica 20.8
> Tin Oxide 43.7
> Zinc Oxide 1.0
> Potassium Dichromate 1.6
>
> Mixing: Weigh out the ingredients in grams or pounds. Dry
> mix by hand or in a ball mill for five minutes, then place in a
> crucible and calcine to cone 8. After calcining, place in a ball
> mill and dry grind for four to five hours. Do not undergrind
> any stain as most stains of this type must be finely ground to
> give true colours. After grinding mix the stain with water to
> the consistency of milk and sieve through a 200 mesh screen.
> It is now ready to use for spraying or brushing an entire pot.
> It needs to be the consistency of condensed milk for
> underglaze painting. Hope this helps Ralph in PE SA.
Michael Banks on sun 2 may 99
The colourant in this stain is generated by a reaction between of chromic
oxide and tin oxide. Different ratios of the two oxides give a range of
pinks to crimsons. It is likely that the crimson colour is caused by the
chromium VI ion which is this colour. For example the precious gemstone
ruby (alumina) is coloured by small amounts of chromium VI.
Pure chromium VI oxide (CrO3) exists and is reddish crimson in colour, but
melts at 196 degrees C and decomposes to green chromium sequioxide (Cr III
ion) at higher temperatures, - unfortunately for potters. The presence of
tin oxide somehow stabilises the CrVI oxide at high temps.
Michael Banks,
Nelson,
New Zealand
Randall Moody Wrote:
>----------------------------Original message----------------------------
>Thank you! I had just about given up on the whole thing and bought the
Mason
>stain (still an option.) This is the recipe that I have. I am still
>wondering what the colorant is. I deep into the end of semester rush so it
>may be next semester before I get some made and tested, but I will post the
>results on ClayArt. I have found that Potassium Dichromate is bad...very
>bad. But I figure in such a small amount it shouldn't be too bad.
> Again thanks to you and to all who were trying to help me.
>
>> Whiting 23.9
>> Calcium Sulfate 6.5
>> Fluospar 4.5
>> Silica 20.8
>> Tin Oxide 43.7
>> Zinc Oxide 1.0
>> Potassium Dichromate 1.6
>>
>> Mixing: Weigh out the ingredients in grams or pounds. Dry
>> mix by hand or in a ball mill for five minutes, then place in a
>> crucible and calcine to cone 8. After calcining, place in a ball
>> mill and dry grind for four to five hours. Do not undergrind
>> any stain as most stains of this type must be finely ground to
>> give true colours. After grinding mix the stain with water to
>> the consistency of milk and sieve through a 200 mesh screen.
>> It is now ready to use for spraying or brushing an entire pot.
>> It needs to be the consistency of condensed milk for
>> underglaze painting. Hope this helps Ralph in PE SA.
>
Linda Arbuckle on mon 3 may 99
The stain below that has potassium dichromate as the colorant works
because of the interaction of tin and chrome (in the potassium
dichromate). In glazes with high tin (perhaps 5% and higher) and small
amount of chrome, the chrome and tin react to give chrome-tin-pinking
instead of the usual green hues from chrome.
I suspect the potassium dichromate is used because it's soluble and is
dissolved in the materials, not merely suspended in it, so the chrome is
well distributed. But I'd test this glaze with a small percentage of
chrome oxide (0.25? Anyone have any suggestions?). You may get similar
results w/o the solubility hazard. Screen well through a small mesh
screen (80 or higher) to make sure the materials are well-distributed.
Another potential hazard is the fluorspar. Someone on ClayArt a while
back raised the issue of fluorine compounds volatilizing in firing and
ending up giving off small amounts of acid compounds that are a health
hazard, can etch studio windows and are not good for the elements in
electric kilns. See Hamer's "A Potters Dictionary of Materials and
Techniques" under fluorspar. I'd buy the stain ready-made.
> Whiting 23.9
> Calcium Sulfate 6.5
> Fluospar 4.5
> Silica 20.8
> Tin Oxide 43.7
> Zinc Oxide 1.0
> Potassium Dichromate 1.6
--
Linda Arbuckle
Graduate Coordinator, Assoc. Prof.
Univ of FL
School of Art and Art History
P.O. Box 115801, Gainesville, FL 32611-5801
(352) 392-0201 x 219
e-mail: arbuck@ufl.edu
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