MRS SANDRA L BURKE on sun 29 mar 98
Does anyone know of a way to formulate a substitute for gerstly
borate. I am having trouble with a very fickle glaze and suspect that
unstable gerstly borate may be the culprit. the glaze base is as
follows:
Nephy Syenite 47.3
Gerstly borate 27.0
Silica 20.3
EPK 5.4
RIO 2.0
Coblat Oxide 1.0
Rutile 4.0
CMC 1 tsp
When this glaze works it is a beautiful speckled light blue which
breaks reddish brown. The problem is that it is so unpredictable.
I might add that I am firing in an electric kiln, using a kinl setter.
Firing cycle remains the same thouhout subsequent firings. Any
sugestions? Also, I tried using distilled water instead of tap.
Ron Wright on mon 30 mar 98
Try the floating blue recipe, AACC#2, on my web site. It is very similar
to yours, but I have found it to be very dependable.
Ron Wright
3dogs Pottery
3dogspottery@iname.com
http://www.concentric.net/~wrright
MRS SANDRA L BURKE wrote:
>
> ----------------------------Original message----------------------------
> Does anyone know of a way to formulate a substitute for gerstly
> borate. I am having trouble with a very fickle glaze and suspect that
> unstable gerstly borate may be the culprit. the glaze base is as
> follows:
> Nephy Syenite 47.3
> Gerstly borate 27.0
> Silica 20.3
> EPK 5.4
> RIO 2.0
> Coblat Oxide 1.0
> Rutile 4.0
> CMC 1 tsp
> When this glaze works it is a beautiful speckled light blue which
> breaks reddish brown. The problem is that it is so unpredictable.
> I might add that I am firing in an electric kiln, using a kinl setter.
> Firing cycle remains the same thouhout subsequent firings. Any
> sugestions? Also, I tried using distilled water instead of tap.
maggie j jones on mon 30 mar 98
Sandra, what are the problems? Try replacing part of the GB with a boron
frit such as ferro 3134,3195 or 3124. ..3124 is more refractory. test
several combos. I find 3124 and 3134 and GB equal parts the best.
Maggie Jones , Turtle Island Pottery, Black Mtn. NC
mrjj@juno.com
On Sun, 29 Mar 1998 13:40:31 EST MRS SANDRA L BURKE
writes:
>----------------------------Original
>message----------------------------
>Does anyone know of a way to formulate a substitute for gerstly
>borate. I am having trouble with a very fickle glaze and suspect that
>unstable gerstly borate may be the culprit. the glaze base is as
>follows:
> Nephy Syenite 47.3
> Gerstly borate 27.0
> Silica 20.3
> EPK 5.4
> RIO 2.0
> Coblat Oxide 1.0
> Rutile 4.0
> CMC 1 tsp
>When this glaze works it is a beautiful speckled light blue which
>breaks reddish brown. The problem is that it is so unpredictable.
>I might add that I am firing in an electric kiln, using a kinl setter.
> Firing cycle remains the same thouhout subsequent firings. Any
>sugestions? Also, I tried using distilled water instead of tap.
>
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B A HARPER on mon 30 mar 98
Hi -
I have a substitution for Gerstley Borate as :
Boric acid 90.25 (soluble)
Whiting 48.69
I've never tried it, I got it from my calculation software.
- Brian Harper
hal mc whinnie on mon 30 mar 98
you might try to substitute borax for gerstley borate.
i hope to have an article on this problem in a future issue of clay times
-----Original Message-----
From: MRS SANDRA L BURKE
To: Multiple recipients of list CLAYART
Date: Sunday, March 29, 1998 6:53 PM
Subject: Gerstly borate
----------------------------Original message----------------------------
Does anyone know of a way to formulate a substitute for gerstly
borate. I am having trouble with a very fickle glaze and suspect that
unstable gerstly borate may be the culprit. the glaze base is as
follows:
Nephy Syenite 47.3
Gerstly borate 27.0
Silica 20.3
EPK 5.4
RIO 2.0
Coblat Oxide 1.0
Rutile 4.0
CMC 1 tsp
When this glaze works it is a beautiful speckled light blue which
breaks reddish brown. The problem is that it is so unpredictable.
I might add that I am firing in an electric kiln, using a kinl setter.
Firing cycle remains the same thouhout subsequent firings. Any
sugestions? Also, I tried using distilled water instead of tap.
David Hewitt on tue 31 mar 98
Sandra,
One could no doubt produce a number of different recipe to substitute
for Gerstly borate. Out of interest I have chosen here to reformulate
the base recipe that you have given using Ferro frit 3278 to give the
boric oxide content. Because this frit also gives Na2O I have changed
the Nepheline Syenite to Potash Feldspar and added a little Dolomite and
Whiting to top up as necessary the MgO and CaO.
This produced the following recipe:-
Potash Feldspar 18.5
Ferro frit 3278 37.4
Flint/Quartz 10.1
EPK 28.1
Dolomite 4.2
Whiting 1.7
____
100
Using the data in my Glaze Workbook program I get the following formula
for your glaze. Beside this is the formula of the above revised recipe.
Your Base Recipe Revised Recipe
K2O .10 .104
Na2O .43 .426
CaO .37 .370
MgO .10 .100
Al2O3 .58 .580
Fe2O3 trace trace
SiO2 3.95 3.95
P2O5 trace trace
Only testing will show if the results are really as similar as the two
formulae look, particularly with the colouring additions that you use.
David
In message , MRS SANDRA L BURKE writes
>----------------------------Original message----------------------------
>Does anyone know of a way to formulate a substitute for gerstly
>borate. I am having trouble with a very fickle glaze and suspect that
>unstable gerstly borate may be the culprit. the glaze base is as
>follows:
> Nephy Syenite 47.3
> Gerstly borate 27.0
> Silica 20.3
> EPK 5.4
> RIO 2.0
> Coblat Oxide 1.0
> Rutile 4.0
> CMC 1 tsp
>When this glaze works it is a beautiful speckled light blue which
>breaks reddish brown. The problem is that it is so unpredictable.
>I might add that I am firing in an electric kiln, using a kinl setter.
> Firing cycle remains the same thouhout subsequent firings. Any
>sugestions? Also, I tried using distilled water instead of tap.
>
--
David Hewitt
Louis Katz on tue 31 mar 98
Here is you glaze calculated out using Ferro 3191. I doubt that it will
look identical to the original. Gertsley's character I believe is in
part do to its partial solubility.
What cone do you fire to?
Louis
Speckly
Cone ?
Ingredient Amount
Ferro Frit 3191 26.66
Custer Feldspar 39.63
EPK 15.12
Whiting 4.89
silica 6.73
rutile 3.78
cobalt carbonate 1.45
Red Iron Oxide 1.75
Total 100.01
Molecular Formula:
0.496 KNa0 0.524 Al2O3 3.843 SiO2
0.450 CaO 0.459 B2O3 0.205 TiO2
0.003 MgO 0.048 Fe2O3
0.052 CoO 0.001 P2O5
GoodrichDn on tue 31 mar 98
Hi Sandra,
That's Chappell's Floating Blue you're talking about and yes, it's finicky.
Others have reformulated it and I'm sure you'll hear from them if you haven't
already, but some things to take into consideration are:
Your bisque temperature: if you're able to raise the temp (from ^08 to ^04,
for example) the clay will absorb less of the dissolved boron from the glaze,
hence less flux at the clay/glaze interface and the glaze is more likely to
stay on the pot, less likely to crawl.
How new is the glaze? If you're using distilled water as I do, try using
more than enough water to mix the glaze, let it settle for a few days, then
pour off the clear water from the top. You'll also be pouring off dissolved
boron, again lessening the flux content.
What kind of cones are you using? Pyro-bars of consistent thickness are
more appropriate in a kiln-sitter than mini-cones. Some folks like to fire
this glaze at ^5 with small cones rather than the ^6 Chappell recommends.
Since I remove some of the flux, I get good results with ^6 bars.
How thick is the glaze? If you're applying two layers, try to get them as
even as possible. Some thickness is needed to get the blue, but excessive
thickness on the pot seems to invite running. By thickening your glaze mix
with a pinch of epsom salts, removing excess water, and adding 2% Bentonite,
you might just get a glaze that will cover adequately in one coat.
Is the glaze cracking or peeling as it dries? If so, slower drying may
help. If a flake does peel loose, moisten with a soft brush and rub it back
down with a fingertip.
These are all things that have worked for me. I'm looking forward to the
responses of the glaze gurus, to see if there's a gerstley-free reformulation.
Good luck,
Don Goodrich
goodrichdn@aol.com
for examples of a couple of successful FB-glazed pots, see:
http://members.aol.com/goodrichdn/stonware.htm
Gregory D Lamont on tue 31 mar 98
Hi Sandra,
What you have described here is the ever-popular--and
cantankerous--Floating Blue. Two alternative recipes that have eliminated
the crawling problem I was having with it come from Ron Roy and Debra
Cobbeldi (thanks to both of you!). The first reduces the gerstley borate,
the second eliminates it--both by substituting Ferro Frit 3134. Here they
are:
Ron Roy's Floating Blue Rev. 1
-----------------------------
Nepheline syenite 41
Gerstley borate 17
Frit 3134 13
Flint 18 Hazard!
EPK 11 Hazard!
--------
100
Red iron oxide 2
Cobalt carbonate 1.5 Hazard!
Rutile 4
Cobbeldi Floating Blue Rev. 1
-----------------------------
Nepheline syenite 43.26
EPK 13.67 Hazard!
Frit 3134 32.81
Flint 10.26 Hazard!
--------
100
Red iron oxide 2
Cobalt carbonate 1.5 Hazard!
Rutile 4
Epsom salts 2
At 01:40 PM 3/29/98 EST, you wrote:
>----------------------------Original message----------------------------
>Does anyone know of a way to formulate a substitute for gerstly
>borate. I am having trouble with a very fickle glaze and suspect that
>unstable gerstly borate may be the culprit. the glaze base is as
>follows:
> Nephy Syenite 47.3
> Gerstly borate 27.0
> Silica 20.3
> EPK 5.4
> RIO 2.0
> Coblat Oxide 1.0
> Rutile 4.0
> CMC 1 tsp
>When this glaze works it is a beautiful speckled light blue which
>breaks reddish brown. The problem is that it is so unpredictable.
>I might add that I am firing in an electric kiln, using a kinl setter.
> Firing cycle remains the same thouhout subsequent firings. Any
>sugestions? Also, I tried using distilled water instead of tap.
>
David Hewitt on wed 1 apr 98
I see that I inadvertantly left out the B2O3 in the analyses of the
recipes given below. Apologies to all concerned.
David
In message , David Hewitt writes
>----------------------------Original message----------------------------
>Sandra,
>One could no doubt produce a number of different recipe to substitute
>for Gerstly borate. Out of interest I have chosen here to reformulate
>the base recipe that you have given using Ferro frit 3278 to give the
>boric oxide content. Because this frit also gives Na2O I have changed
>the Nepheline Syenite to Potash Feldspar and added a little Dolomite and
>Whiting to top up as necessary the MgO and CaO.
>This produced the following recipe:-
>Potash Feldspar 18.5
>Ferro frit 3278 37.4
>Flint/Quartz 10.1
>EPK 28.1
>Dolomite 4.2
>Whiting 1.7
> ____
> 100
>Using the data in my Glaze Workbook program I get the following formula
>for your glaze. Beside this is the formula of the above revised recipe.
>
> Your Base Recipe Revised Recipe
>K2O .10 .104
>Na2O .43 .426
>CaO .37 .370
>MgO .10 .100
>Al2O3 .58 .580
B2O3 .48 .48
>Fe2O3 trace trace
>SiO2 3.95 3.95
>P2O5 trace trace
>
>Only testing will show if the results are really as similar as the two
>formulae look, particularly with the colouring additions that you use.
>David
>
>In message , MRS SANDRA L BURKE writes
>>----------------------------Original message----------------------------
>>Does anyone know of a way to formulate a substitute for gerstly
>>borate. I am having trouble with a very fickle glaze and suspect that
>>unstable gerstly borate may be the culprit. the glaze base is as
>>follows:
>> Nephy Syenite 47.3
>> Gerstly borate 27.0
>> Silica 20.3
>> EPK 5.4
>> RIO 2.0
>> Coblat Oxide 1.0
>> Rutile 4.0
>> CMC 1 tsp
>>When this glaze works it is a beautiful speckled light blue which
>>breaks reddish brown. The problem is that it is so unpredictable.
>>I might add that I am firing in an electric kiln, using a kinl setter.
>> Firing cycle remains the same thouhout subsequent firings. Any
>>sugestions? Also, I tried using distilled water instead of tap.
>>
>
>--
>David Hewitt
>
--
David Hewitt
MRS SANDRA L BURKE on thu 2 apr 98
Hi Don,
Thanks for your suggestions. I do bisque to cone 04. I'm using an
electric kiln with an automatic cone sitter and firing to the temp
reccomended by the manual, whiich according to all my other charts,
is somewhere around a cone 5, not a ture ^6.
The glaze was freshly mixed when I glazed the last pieces. My other
batch was working fine until one of my students double-dipped several
pots with a saturated iron oxide glaze into it. Now I can't repeat
the original results. I never considered pouring off the water on the
top or adding epson salts. If that works it will save alot of cobalt,
as I mix up large buckets of glazes once I have run initial batch
tests.
No the glaze does not normall crack or peel, unless of course a
student puts on an excessively thick coat.
Well thanks again for your help
Sanra B
JLHclay on fri 3 apr 98
What is the cone range for Floating Blue & Cobbedi floating blue? What
results in gas firings? jlhclay Tucson 4:30am wide awake.
MRS SANDRA L BURKE on sat 4 apr 98
It's a cone5/6 oxidation. I have not tried it in reduction as we only
have two electric kilns at the school.
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