Pat Chesney on mon 6 oct 97
Sorry, I wrote down the formula wrong. I ran it through HyperGlaze and saw
that I hadn't given the right formula. Here it is below.
>Glaze name: Bright Blue
>Cone: 10
>Color: Opaque Blue
>
>Surface texture: Shiny or Glossy
>Firing: Ox. or Red.
>Glaze type:
>
>Recipe: Percent Batch
>Custer Feldspar 34.65 173.2
>Gerstley Borate 9.90 49.5
>Whiting 14.85 74.2
>EPK 4.95 24.7
>Flint 34.65 173.2
>Bentonite 0.99 4.9
>Totals: 100.00 % 499.9 Gm
>
>Also add:
>Cobalt oxide 1.00 5.0
>
>Comments:
>This glaze does great in oxidation. It turns matt when thick in reduction
>and it tries to crawl sometimes.
>
>Unity Formula for Bright Blue:
>0.150 K2O 0.308 Al2O3 4.166 SiO2
>0.099 Na2O 0.162 B2O3 13.5:1 Si:Al Ratio
>0.747 CaO
>0.004 MgO
>
>Percentage Analysis:
> 70.44 % SiO2
> 8.84 % Al2O3
> 3.15 % B2O3
> 3.97 % K2O
> 1.72 % Na2O
> 11.80 % CaO
> 0.06 % MgO
I notice that the clay content is low. Could this be a factor? I have found
another, untested recipe for a bright blue that has:
Soda feldspar 13.51
Silica 28.12
whiting 18.24
kaolin 10.13
cobalt carb 1
red iron 1
>Unity Formula for Gloss Dark Blue:
>0.084 K2O 0.460 Al2O3 3.969 SiO2
>0.172 Na2O 8.6:1 Si:Al Ratio
>0.743 CaO
>
>Percentage Analysis:
> 69.00 % SiO2
> 13.57 % Al2O3
> 2.29 % K2O
> 3.10 % Na2O
> 12.07 % CaO
Does this look better to the glaze heavies? I know that there are some that
_hate_ Gerstley Borate, but it does fine in our other glazes in the wood
fire.
Sorry for the mixup.
Pat Chesney
Pat-Chesney@easy.com
Waco, Texas
rballou@mnsinc.com on tue 7 oct 97
Hi Pat,
What's the cooling rate on the wood kiln? As I recall, this is a hard brick
kiln. A slow cooling combined with the low alumina content of the glaze is
conducive to the formation of micro crystals, giving a mat appearance. So,
I think you're right, go a glaze with a higher alumina content if you want
glossiness. But you might get some interesting effects with this glaze by
adding some rutile or titanium. You may have to ball mill the glaze to get
rid of the speckling.
The second glaze you list looks promising. I've tried to compare it to the
tiles I have from the Currie glaze testing I'm doing. It falls between the
..8 and .7 Calcium sets, so a direct reading isn't possible, but glazes in
that area of the al/si ratio on both tiles are glossy. In addition,
translucency in this area is affected by small changes in the
alumina/silica ratio. Crazing is evident on the .7 CaO samples. Of course,
clay body is a big factor in crazing.
Here's a glaze for further testing from the .8 CaO set that is glossy,
craze free, with just a little loss of translucency:
..8Cao Set, Glaze #19, from Currie: Stoneware Glazes, A Systematic Approach
28.07 Custer Spar
20.20 Whiting
15.49 Kaolin (EPK)
36.25 Silica
Hope this helps.
Ruth Ballou
rballou@mnsinc.com
In Silver Spring, MD where Indian Summer has arrived
>----------------------------Original message----------------------------
>Sorry, I wrote down the formula wrong. I ran it through HyperGlaze and saw
>that I hadn't given the right formula. Here it is below.
>
>>Glaze name: Bright Blue
>>Cone: 10
>>Color: Opaque Blue
>>
>>Surface texture: Shiny or Glossy
>>Firing: Ox. or Red.
>>Glaze type:
>>
>>Recipe: Percent Batch
>>Custer Feldspar 34.65 173.2
>>Gerstley Borate 9.90 49.5
>>Whiting 14.85 74.2
>>EPK 4.95 24.7
>>Flint 34.65 173.2
>>Bentonite 0.99 4.9
>>Totals: 100.00 % 499.9 Gm
>>
>>Also add:
>>Cobalt oxide 1.00 5.0
>>
>>Comments:
>>This glaze does great in oxidation. It turns matt when thick in reduction
>>and it tries to crawl sometimes.
>>
>>Unity Formula for Bright Blue:
>>0.150 K2O 0.308 Al2O3 4.166 SiO2
>>0.099 Na2O 0.162 B2O3 13.5:1 Si:Al Ratio
>>0.747 CaO
>>0.004 MgO
>>
>>Percentage Analysis:
>> 70.44 % SiO2
>> 8.84 % Al2O3
>> 3.15 % B2O3
>> 3.97 % K2O
>> 1.72 % Na2O
>> 11.80 % CaO
>> 0.06 % MgO
>
>I notice that the clay content is low. Could this be a factor? I have found
>another, untested recipe for a bright blue that has:
>
>Soda feldspar 13.51
>Silica 28.12
>whiting 18.24
>kaolin 10.13
>
>cobalt carb 1
>red iron 1
>
>>Unity Formula for Gloss Dark Blue:
>>0.084 K2O 0.460 Al2O3 3.969 SiO2
>>0.172 Na2O 8.6:1 Si:Al Ratio
>>0.743 CaO
>>
>>Percentage Analysis:
>> 69.00 % SiO2
>> 13.57 % Al2O3
>> 2.29 % K2O
>> 3.10 % Na2O
>> 12.07 % CaO
>
>Does this look better to the glaze heavies? I know that there are some that
>_hate_ Gerstley Borate, but it does fine in our other glazes in the wood
>fire.
>
>Sorry for the mixup.
>
>Pat Chesney
>Pat-Chesney@easy.com
>Waco, Texas
Ron Roy on sat 11 oct 97
Hello Pat - I have been trying to send this to you but keep getting a
message saying your sight is closed because of spamming - hope nobody else
reads it!
Pat -are you trying to drive me crazy - first you left out the silica - OK
I figured that out but in the second one the F4 should be 43.51 - right.
Any way the first one looks OK to me I can't imagin why it is going matte -
are you sure about your materials - Are you taking the glaze for both
firings out of the same bucket. It's got me stumpted - even if the wood
kiln is cooling slower I still can't imagine that glaze going matte - it
looks just fine to me as a gloss glaze at cone 10. Adding more GB in a line
blend +1 +2 +3 would certainly make it more glossy - test it first and
watch for running where thick.
Is it going matte where the ash is landing on it? I could do better if I
could see a sample.
>----------------------------Original message----------------------------
>Sorry, I wrote down the formula wrong. I ran it through HyperGlaze and saw
>that I hadn't given the right formula. Here it is below.
>
>>Glaze name: Bright Blue
>>Cone: 10
>>Color: Opaque Blue
>>
>>Surface texture: Shiny or Glossy
>>Firing: Ox. or Red.
>>Glaze type:
>>
>>Recipe: Percent Batch
>>Custer Feldspar 34.65 173.2
>>Gerstley Borate 9.90 49.5
>>Whiting 14.85 74.2
>>EPK 4.95 24.7
>>Flint 34.65 173.2
>>Bentonite 0.99 4.9
>>Totals: 100.00 % 499.9 Gm
>>
>>Also add:
>>Cobalt oxide 1.00 5.0
>>
>>Comments:
>>This glaze does great in oxidation. It turns matt when thick in reduction
>>and it tries to crawl sometimes.
>>
>>Unity Formula for Bright Blue:
>>0.150 K2O 0.308 Al2O3 4.166 SiO2
>>0.099 Na2O 0.162 B2O3 13.5:1 Si:Al Ratio
>>0.747 CaO
>>0.004 MgO
>>
>>Percentage Analysis:
>> 70.44 % SiO2
>> 8.84 % Al2O3
>> 3.15 % B2O3
>> 3.97 % K2O
>> 1.72 % Na2O
>> 11.80 % CaO
>> 0.06 % MgO
>
>I notice that the clay content is low. Could this be a factor? I have found
>another, untested recipe for a bright blue that has:
>
>Soda feldspar 13.51
>Silica 28.12
>whiting 18.24
>kaolin 10.13
>
>cobalt carb 1
>red iron 1
>
>>Unity Formula for Gloss Dark Blue:
>>0.084 K2O 0.460 Al2O3 3.969 SiO2
>>0.172 Na2O 8.6:1 Si:Al Ratio
>>0.743 CaO
>>
>>Percentage Analysis:
>> 69.00 % SiO2
>> 13.57 % Al2O3
>> 2.29 % K2O
>> 3.10 % Na2O
>> 12.07 % CaO
>
>Does this look better to the glaze heavies? I know that there are some that
>_hate_ Gerstley Borate, but it does fine in our other glazes in the wood
>fire.
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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