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I use a lot of clear and have been on the hunt for clay/clear glaze fit for some time.  I started out using the clear from MC6, but found that on some white clays both porcelain and stoneware, I would get crazing.  I thought I had a good fit with Nara 5 porcelain and that clear recipe but discovered that crazing would appear later, not immediately.  I have switched to Laguna's #16 porcelain, and at this point, I am not getting crazing, but......I am going to do that boiling/freezing test to see what happens.  Laguna doesn't seem to list the COE.

In my quest for a better clear, I discovered that MC6 had another recipe using G200HP (which is what I have) so I mixed that and noticed no difference whatsoever. 

After all that, here is my question, I met a potter in Denver who works exclusively with Laguna #16 and uses one of the Low Expansion clears in John Britt's book on page 77.  She said it was so she would NOT have crazing.  If the clear has a low COE 5.54 or 5.71 doesn't that mean it would not expand as much and be prone to crazing?? 

Just sign me,

Seriously Confused

 

aka Roberta

 

Clear Recipe from MC6

G200 feldspar       20

FF 3134                20

Wollastonite          15

EPK                       20

talc                         6

Silica                      19

 

I just found information on my question in the book MC6 on page 99.  I have found that some things simply do not make sense to me until I am either ready to use it or have enough prior knowledge to utilize new info.  :rolleyes: 

 

I really do need a good glaze class and tutoring in Insight (or something)  yep.

 

r.

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Crazing occurs in the final cooling phase - under 300 degrees celsius.  It is the glaze contracting more than the body.  So beyond the glaze recipe consider:

1. clay body compatibility

2.  Insulation, such as blanket the kiln to slow down cooling particularly at the final stages.

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