Crackle Glazes In Oxidation...

[HAUKSBEE]

Looking for a good white, or translucent, or transparent, crackle glaze base for electric firing. Cones 6-10. Thanks.

[hansen]

Looking for a good white, or translucent, or transparent, crackle glaze base for electric firing. Cones 6-10. Thanks.

 

 

I haven't tested these but they are in my recipe collection.

 

Kenneth ClarkCrackle - cone 9

 

80 soda spar

 

10 kaolin

 

10 whiting

 

 

 

Snowflake Crystal

 

80 Custer

 

10 silica

 

10 whiting

 

+5 bentonite

 

 

 

Chinese Crackle

 

83 Custer Feldspar

 

8 Silica

 

9 Whiting

 

For white add:

 

10 Zircopax

 

 

 

h a n s e n

p.s. so if you test the please reply with images of test tiles, etc. so the group can see? We were elsewhere discussing the importance of feed-back and how to keep everyone on board - there are lots of sites on the net that have examples of different types of test tile photographs -

 

 

 

[HAUKSBEE]

I will post my results, thank you.

 

R.G.Kelley

 

 

[Matt Katz]

Crazing (Crackle) occur independent of atmosphere and performance is unreliable based solely on glaze formula. This is because Crazing (crackle) forms as a result of the fit of the glaze to the clay body. A.K.A. Your results may vary.

[hansen]

Crazing (Crackle) occur independent of atmosphere and performance is unreliable based solely on glaze formula. This is because Crazing (crackle) forms as a result of the fit of the glaze to the clay body. A.K.A. Your results may vary.

 

 

Guan crackle ware from the Southern Song dynasty 12th century AD were produced in large quantities in Longquan and Jingdezhen responding to Ru ware in the north (10th to 11th century). Ru ware being an icy, "cicada wing" pattern. Guan was often deeply reduced, giving "iron wire and golden thread". (see Nigel Wood for UPAs of glazes and bodies, ppg. 82, 84, 88, 127) This was not achieved by altering the thermal expansion/contraction ratio but instead by under-firing. This is natural because the ideal glaze is under slight tension, not torsion, nor a perfect fit. Firing normally was of a length that this crazing (which is what crackle is) healed over.

 

h a n s e n

 

 

 

[hansen]

What Matt says is true since some educational communities use clay bodies with excessive shrinkage beyond the norm, certain schools come to mind, because the clay is overly plastic which gives the students an over-inflated egotistical sense of awe and wonder about their throwing ability. Such clays will shrink a good 15% or more - this of course will make cautionary remarks like Matt's more relevant than what in most other communities might be expected. I can see where he is coming from. Matching co-oefficients of shrinkage and expansion are what will make a glaze "fit" or not, and crackle is an "almost" fit of a certain nature. Does this make sense?

 

h a n s e n

 

 

 

Crazing (Crackle) occur independent of atmosphere and performance is unreliable based solely on glaze formula. This is because Crazing (crackle) forms as a result of the fit of the glaze to the clay body. A.K.A. Your results may vary.

 

 

Guan crackle ware from the Southern Song dynasty 12th century AD were produced in large quantities in Longquan and Jingdezhen responding to Ru ware in the north (10th to 11th century). Ru ware being an icy, "cicada wing" pattern. Guan was often deeply reduced, giving "iron wire and golden thread". (see Nigel Wood for UPAs of glazes and bodies, ppg. 82, 84, 88, 127) This was not achieved by altering the thermal expansion/contraction ratio but instead by under-firing. This is natural because the ideal glaze is under slight tension, not torsion, nor a perfect fit. Firing normally was of a length that this crazing (which is what crackle is) healed over.

 

h a n s e n