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Correcting Crazing In Glaze


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#1 jwlceramics

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Posted 11 April 2011 - 10:23 AM

I have two cone 04 clear glazes that I am trying to eliminated crazing from.
1st glaze formula-
Gerstley Borate 25
Ferro Frit 3124 25
Soda Feldspar 20
Cornwall Stone 20
Whiting 5
zinc Oxide 5

2nd glaze formula-
Gerstley Borate 26
Lithium Carbonate 4
Ferro Frit 3124 30
Neph Sy 20
EPK 10
Flint 10

Clay Body-
Tile #6 30
Neph Sy A400 25
KT om4 Ball Clay 20
Holmes Fredeick Fireclay 15
Cedar Heightd Fireclay 10

Any Suggestion? Thanks

#2 Natas Setiabudhi

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Posted 12 April 2011 - 06:01 AM

Crazing is sometimes glaze failure which hard to remedy. You have some alternatives to remedy crazing: change, increase, or decrease some oxides in your body or glaze formula. For first glaze formula, i think you may decrease soda feldspar 5-10% and increase whiting 5-10% (the proportion is must 100%). For second one, you may decrease nepheline sy 5-10 and increase flint 5-10%. Another thing is crazing can be caused by under vitrified body, meanwhile the glaze on it is vitrified (fused). For example, you use the body stoneware (high temperature), meanwhile the temperature glaze is low.

Good luck :rolleyes:
Natas Setiabudhi
Kupu Ceramic Studio, Indonesia
www.butterflyceramic.blogspot.com

#3 Marcia Selsor

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Posted 18 April 2011 - 07:00 AM

You can adjust the silica. Crazing is caused by I'll fitting glaze.
marcia

#4 Pres

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Posted 19 April 2011 - 10:33 AM

I have two cone 04 clear glazes that I am trying to eliminated crazing from.
1st glaze formula-
Gerstley Borate 25
Ferro Frit 3124 25
Soda Feldspar 20
Cornwall Stone 20
Whiting 5
zinc Oxide 5

2nd glaze formula-
Gerstley Borate 26
Lithium Carbonate 4
Ferro Frit 3124 30
Neph Sy 20
EPK 10
Flint 10

Clay Body-
Tile #6 30
Neph Sy A400 25
KT om4 Ball Clay 20
Holmes Fredeick Fireclay 15
Cedar Heightd Fireclay 10

Any Suggestion? Thanks




One other thing to look at with crazing is the firing cycle.Sometimes a kiln that is cooled too quickly will craze the pottery because of the quick contraction not allowing the glaze to adjust. Do you open your kiln when still hot? Is your kiln in an area that allows it to cool quickly-ex cold outside garage etc. If so you may need to let the kiln cool naturally to room temp, or fire it down by leaving one element on for part of your fire down-hard to do if you are using a sitter, but possible by propping the sitter.

Simply retired teacher, not dead, living the dream. on and on and. . . . on. . . .                                                                                 http://picworkspottery.blogspot.com/





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