[Clayart] Zinc and Mimi - RR

[William Schran]

Ron,
Having worked with crystalline glazes rather extensively where the
glaze contains about 25% zinc I do two things to help with dry
shrinkage of the glaze on the pot that can cause cracking on the
surface and crawling. First, I only use calcined zinc oxide. Second, I
initially wet the dry glaze with a gum solution, usually CMC and then
add water to achieve proper consistency. The gum solution helps to
prevent the crystalline glaze, that contains little or no clay, to
bind to the pot and prevent cracking/peeling as the glaze dries and
shrinks.
Bill

William Schranwschran at twc.com703-505-1617

	-----------------------------------------From: ronroy at ca.inter.net
To: "Clayart international pottery discussion forum"
Cc: 
Sent: Sunday September 5 2021 1:46:55PM
Subject: [Clayart] Zinc and Mimi - RR

 I have two questions!

 Does anyone have a copy of Mimi Obstler's book "Out of the Earth Into
 the Fire" that they would like to sell. I have a customer for you.

 Has anyone had the unfortunate problem with a glaze fluxed with zinc
 oxide - where the glaze starts to crawl after being in the bucket for
 a while? Apparently zinc oxide re-hydrates and shrinks excessively
 causing crawling problems.

 Has anyone had the problem and found a solution?

 OK - that's three questions

 Thanks for any enlight enment!

 RR

 Ron Roy
 ronroy at ca.inter.net
 Web page ronroy.net


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