[Clayart] Zinc and Mimi - RR

William Schran wschran at twc.com
Tue Sep 7 02:53:34 UTC 2021

Not dumb at all!
I first explored crystalline glazes back in the 1970's when there was
not much current information in libraries. Had a horrible time getting
a thick application of glaze not to crack and peel. Tried couple ways
and ran across information about adding gum binder to glazes...
I mix CMC with hot water using a tableware serving spoon that I guess
is about a tablespoon + a teaspoon to plastic mayo jars (30 oz size)
containing hot water. Give a shake up then let sit to wet all the dry
CMC for a couple days.
With my crystalline glazes I add approx. 1/4 cup CMC solution to
100-200 grams dry glaze, stir and sieve and add water as needed to get
brushable consistency.

	-----------------------------------------From: "sumi" 
To: clayart at lists.clayartworld.com
Sent: Monday September 6 2021 7:40:39PM
Subject: Re: [Clayart] Zinc and Mimi - RR


 How do you initially wet the dry glaze with CMC solution? I have CMC
 solution which I made by mixing CMC into hot water; but do you add a
 spoonfuls of this to a couple of quarts of water and mix it into your
 dry glaze to create a thick slurry? And then add more water? Sorry,
 I write it down it sounds like a dumb question.

 > 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
 > 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
 > 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
 > oxide - where the glaze starts to crawl after being in the bucket
 > 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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