Mike Carroll on tue 19 may 98
Gloria,
A number of years ago a professor at Rochester Inst. of Tech. gave me a
formula, ^6, to use with Mason Stains. I use it as a clear coat and with
additions for a blue green glaze. The formula looked familiar and I went
back through some notes and found a reference to a Cermics Monthly article,
Summer issue of 1981, pg.78, by Melvin Rowe. This is a pretty neat base
recipe with a lot of simple variations.
Gerstly Borate 50
Kaolin 20
Silica 30
In my studio, I'm firing about ^5 and I use a variation of this.
Gerstly Borate 50
Kaolin 17.5
Silica 32.5
If you can't find the issue I could mail a copy.
Mike
Avon NY
Ron Roy on mon 25 may 98
I know I'm late with this but just got back in town.
There are some problems with this glaze - too much GB and too much boron as
well. I don't believe it would be wise to count on it being food safe with
some colouring additions.
Having that much GB in a glaze is bound to present problems with the slop
after a period of time.
Couple all that with the variability of the GB and trouble can be expected.
I have also had experience fixing this type of glaze because of it's low
expansion - there are better cone 6 clear glazes.
I have some versions of a clear cone 6 glaze that we will be testing at
Canador this summer. I think these are going to fulfill all the criteria
that are required for a cone 6 clear on many cone 6 bodies - but you will
have to test it on your own - repeat - you will have to try it first on the
bodies you are using - and test it for fit.
The other issues I feel are dealt with are durability, all colours
(including reds) should work well.
If anyone tries these I would appreciate any comments on how they work - as
a clear glaze, if stains or underglaze look as they are supposed to and any
reactions with the clays you are using. You can post to the list or to me
directly.
RR cone 6 CD #1
-----------------
F4 SPAR............. 37.00
Gers Borate 9/97.... 5.00
F3134............... 10.00
WOLAST.............. 15.00
EPK................. 17.00
SILICA.............. 16.00
----------
100.00
RATIO 7.48
EXPAN 445.20
WEIGHT 294.96
% CaO 10.42
%B2O3 3.89
RR cone 6 CD #3
-----------------
F4 SPAR............. 36.00
Gers Borate 9/97.... 4.00
F3134............... 12.00
WOLAST.............. 15.00
EPK................. 18.00
SILICA.............. 15.00
----------
100.00
RATIO 7.35
EXPAN 448.56
WEIGHT 290.06
% CaO 10.42
%B2O3 3.89
Some say that wolastonite helps cure bubble problems in clear glazes at
cone 6 but I have not seen any confirmation of this in my experiments so
here is CD #3 without the wolastonite incase anyone is interested in doing
both versions.
RR cone 6 CD #3 no wol.
-----------------
F4 SPAR............. 34.00
Gers Borate 9/97.... 4.00
F3134............... 12.00
WHITING............. 11.00
EPK................. 17.50
SILICA.............. 21.50
----------
100.00
RATIO 7.45
EXPAN 449.01
WEIGHT 91.31
% CaO 10.42
%B2O3 3.89
>----------------------------Original message----------------------------
>Gloria,
>
>A number of years ago a professor at Rochester Inst. of Tech. gave me a
>formula, ^6, to use with Mason Stains. I use it as a clear coat and with
>additions for a blue green glaze. The formula looked familiar and I went
>back through some notes and found a reference to a Cermics Monthly article,
>Summer issue of 1981, pg.78, by Melvin Rowe. This is a pretty neat base
>recipe with a lot of simple variations.
>
>Gerstly Borate 50
>Kaolin 20
>Silica 30
>
>In my studio, I'm firing about ^5 and I use a variation of this.
>
>Gerstly Borate 50
>Kaolin 17.5
>Silica 32.5
Ron Roy
93 Pegasus trail
Scarborough Otario
Canada M1G 3N8
Phone: 416-439-2621
Fax: 416-438-7849
Web page: Home page http://digitalfire.com/education/people/ronroy.htm
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