Craig Edwards on sat 22 feb 97
------------------
Hello=3B
Earlier this week the glaze =22Cream breaking Red=22 ---Cone 6,or 7 maybe =
even 5
or fired to 2195 in 4hours 9 minutes and soaked for 35 minutes.
35 Gerstley Borate
15 Soda Spar
10 Whiting
5 Barium Carb
10 Flint
13 Tin
2 rio
I'm sort of interested in using this glaze. Maybe changing the Barium to
Strontium for the safety factor. The material that slows me down ablit is =
the
high level of tin oxide--------It costs soooooo much. At 13 parts the =
expense
is up there. And as I have a tendancy for using alot of a glaze when I find =
one
that I like, cost is a factor.
Casting about looking for a cheap source of Tin, the best I have been able =
to
find is =247.00 a lb.------ still high but loking within grasp.
I am thinking of doing a line blend with the tin to find the lowenst =25 =
that will
still give the results, also maybe some substitution of Mason stain or =
Zircopax.
Has anyone out there in clayland experimented withthis glaze or have a good
source of Tin, or for that matter any insights into this glaze. Any help =
would
be greatly appreciated.
Sunny and a warm 33 degrees in MN
Craig Edwards
cedwards=40willmar.com
Roeder on sun 23 feb 97
Regarding the Cream Breaking Red recipe below, I've substituted Strontium
for the Barium, (I multiply the barium requirement times .75 to get the
amount of strontium to use). Works fine. I, too, was concerned about the
cost of tin oxide and tried various zircopax, superpax replacements. While
you still get "a beige" glaze, you do lose the mottling and "depth". Much
more attractive with the tin.
I believe Ron Roy (or some other glaze expert) commented on this glaze
before, saying it was too low in silica or something...that it was "at best"
a cone 04??? The version with strontium was better than the barium version,
silica-wise, but still not good. Probably not safe for food. Something to
the effect that if you take two test tiles out of the kiln and put one in
the dishwasher for many loads, that you could easily see that a change has
occured in the one that has been repeatedly washed....Does this sound
familiar to anyone? Have I gotten the gist?
I used this glaze a number of years ago on some items I've used in my own
kitchen. Never did sell it to the public. It is interesting though, that
the couple items I've been running through the dishwasher for 5 years really
look the same as the ones that haven't been washed. Strange.
I would be interested in hearing, once again, the problems with this glaze
analysis-wise, since there seems to be a number of you out there who intend
to use it.
Candice Roeder
snowing in Michigan again
>----------------------------Original message----------------------------
>------------------
>Hello;
>
>Earlier this week the glaze "Cream breaking Red" ---Cone 6,or 7 maybe even 5
>or fired to 2195 in 4hours 9 minutes and soaked for 35 minutes.
>
>35 Gerstley Borate
>15 Soda Spar
>10 Whiting
>5 Barium Carb
>10 Flint
>13 Tin
>2 rio
>
>I'm sort of interested in using this glaze. Maybe changing the Barium to
>Strontium for the safety factor. The material that slows me down ablit is the
>high level of tin oxide--------It costs soooooo much. At 13 parts the expense
>is up there. And as I have a tendancy for using alot of a glaze when I find one
>that I like, cost is a factor.
>Casting about looking for a cheap source of Tin, the best I have been able to
>find is $7.00 a lb.------ still high but loking within grasp.
>I am thinking of doing a line blend with the tin to find the lowenst % that
will
>still give the results, also maybe some substitution of Mason stain or
Zircopax.
>
>Has anyone out there in clayland experimented withthis glaze or have a good
>source of Tin, or for that matter any insights into this glaze. Any help would
>be greatly appreciated.
>
>Sunny and a warm 33 degrees in MN
>
>Craig Edwards
>cedwards@willmar.com
>
Ron Roy on sun 23 feb 97
>----------------------------Original message----------------------------
>------------------
>Hello;
>
>Earlier this week the glaze "Cream breaking Red" ---Cone 6,or 7 maybe even 5
>or fired to 2195 in 4hours 9 minutes and soaked for 35 minutes.
>
>35 Gerstley Borate
>15 Soda Spar
>10 Whiting
>5 Barium Carb
>10 Flint
>13 Tin
>2 rio
>
>I'm sort of interested in using this glaze. Maybe changing the Barium to
>Strontium for the safety factor. The material that slows me down ablit is the
>high level of tin oxide--------It costs soooooo much. At 13 parts the expense
>is up there. And as I have a tendancy for using alot of a glaze when I find one
>that I like, cost is a factor.
>Casting about looking for a cheap source of Tin, the best I have been able to
>find is $7.00 a lb.------ still high but loking within grasp.
>I am thinking of doing a line blend with the tin to find the lowenst %
>that will
>still give the results, also maybe some substitution of Mason stain or
>Zircopax.
>
>Has anyone out there in clayland experimented withthis glaze or have a good
>source of Tin, or for that matter any insights into this glaze. Any help would
>be greatly appreciated.
Hope you are not planning to use this on functional ware. There is nowhere
near enough alumina or silica to make this a durable glaze. I will
personally guarantee this will leach Barium and any other poison in this
glaze. Even on the outside of pots it will change with washing. Beware
which mason stains you use - - some will have toxins which will come out of
this glaze.
On the other hand - as a decorative glaze on none functional clay .........
Just make sure any ware which may be used for food is sold with a warning.
You can take out the 5 Barium and replace it with 2 more Whiting (that
means the new glaze will have 12 whiting instead of 10. I am guessing the
glaze will look the same and it will be a cheaper fix than the strontium.
If you go with a Strontium sub then 3.5 is the right amount.
I strongly advise anyone not to use this glaze with the Barium in it.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
Tom Buck on wed 16 sep 98
Judith:
Your memory did not let you down. I posted the piece in Feb 97.
And here it is again with slight changes to make it stand by itself rather
than as part of a thread at that time:
-------------
Because he uses and teaches glaze calculation via computer software,
Ron Roy sees a glaze not as a batch recipe but as a Seger (Flux Unity)
Formula, and immediately seeks to see where the glaze fits into a
specific firing range. He does so by comparing the glaze's Seger
formula to well established data in the literature. (See books by
Cooper, Hansen, Hamer, Zakin, others).
In a firing, the raw materials (most of them) change
into essential oxides that hopefully will melt into liquid at high
temperature and then these oxides, molecule by molecule, will join
(be incorporated into) the growing huge molecule called glass, some
characteristics of which Ron discussed.
The glaze being discussed "Cream Breaking Red" C6 Ox was cited
as the following:
Batch recipe Seger formula (boria, B2O3, not a flux)
35 Gerstley borate CaO 0.67 Fe2O3 0.04 SiO2 1.21
15 Kona F-4 feldspar MgO 0.09 B2O3 0.44 SnO2 0.27
10 Whiting BaO 0.08 Al2O3 0.10
5 Barium carbonate KNaO 0.16
10 Flint (Total= 1.00)
13 Tin Oxide
2 Iron oxide red Ratio SiO2:Al2O3 = 12.1
Expansion=8.8x10E-6 without effect of Tin Oxide,
likely to lower it to approx. 8 x10E-6.
Zakin cites R.Schmitt's limit data for Cone 3-5 (Transparent to Glossy)
as follows in molecular (Seger) values:
CaO 0.05-0.4; Na2O 0.05-0.4; K2O 0.05-0.4; Li2O 0.0-0.1; ZnO 0.0-0.1;
BaO 0.0-0.05; MgO 0.0-0.05; PbO 0.0-0.5; SrO 0.0-0.4. Any
combination of these flux oxides that total 1.0 is expected to produce
a "balanced" mature glaze when combined with
Neutral/amphoterics Al2O3 0.2-0.3; B2O3 0.0-0.5; and
Glass-formers: SiO2 2.0 - 3.0.
Using these criteria, the Cream Breaking Red glaze fails in every major
oxide category: In the flux oxide group, CaO is too high; the Al2O3 is
half what it should be; and the SiO2 at 1.2 is well below 2.0 minimum
(although the Tin Oxide compensates in part).
If a glaze contains considerable boria (and this one does), it often
helps to include boria as a flux (as Ron did):
Seger formula, boria as flux
Fluxes: CaO 0.46; MgO 0.07; BaO 0.05; KNaO 0.11; B2O3 0.31 (=1.00);
Neutral/amphoterics: Fe2O3 0.03; Al2O3 0.07;
Glass-formers: SiO2 0.84; SnO2 0.19.
Now, Cooper's limit data applies: Fluxes--CaO 0-0.55; MgO 0-0.325;
KNaO 0-0.375; ZnO 0-0.3; BaO (SrO) 0-0.4; B2O3 0-0.35;
Amphoterics: Al2O3 0.275 - 0.65; Glass-formers: 2.4 - 4.7.
Using Cooper's criteria, the Cream Breaking Red glaze falls within the
limits for flux oxides but is drastically low in Al2O3 and SiO2.
So, as Ron Roy concluded, this glaze is not suitable for coating
functional ware to be used in food service.
It may be useful to see how a likely candidate for food-use might look;
the following is one of many that could be designed:
Cone 6 glossy glaze based on Cream Breaking Red
Batch recipe Seger formula (boria not a flux)
41.0 G200 (or equal) CaO 0.58 Fe2O3 0.05 SnO2 0.30
22.0 Gerstley borate MgO 0.07 Al2O3 0.28 SiO2 3.11
9.0 Whiting KNaO 0.28 B2O3 0.31
3.0 Strontium carb. SrO 0.07
25.0 Flint
13.0 Tin Oxide
2.0 Iron oxide red Ratio SiO2:Al2O3 = 11.1 Expn= 7.3 x10E-6
Good glaze testing.
Tom Buck ) tel: 905-389-2339
& snailmail: 373 East 43rd St. Hamilton ON L8T 3E1 Canada
(westend Lake Ontario, province of Ontario, Canada).
Alisa Liskin Clausen on sat 21 sep 02
Dear Dawn and Clayart
This was a glaze that I liked on the test tiles but the big batch was =
scratched.
The color was beige with an iron red break over the rims and textures. =
However,
it pinholed inside all of the vessels. I mixed it again, same big batch =
results.
When I tested Ron and John's Bone, with my frit, it breaks and streaks =
and red.
Marianne is testing this glaze with the addition of 7% Barium,(I know, I =
know) because that is what my
Frit contains.
Tony Hansen's 20 x 5 with 10% Zircopax is a glaze I use a lot of of. =
However, I find it to be a more
milky white gloss than cream.
regards from Alisa in Denmark
still reading only from the archives.
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