Correcting Crazing In Glaze

[jwlceramics]

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

[Natas Setiabudhi]

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

[Marcia Selsor]

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

marcia

[Pres]

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.