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Glaze Sintering


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Not intended as an answer, just adding to the discussion.


A vague memory of the term Tamman temperature lead me to this:

minimum cone for sintering cone 10 glazes



... which implies the idea of sintering may -- for some glazes at least -- not be the really great idea it sounds.

I have found that there is considerable difference in the way
different glazes act to sintering, Some harden up and stick well at
cone 04. Others want to fall off in sheets. Shinos did not work at
all and I decided to put them on at the kiln site.

I have had the same experience. I don't think 04 will
help. A sintered glaze can be more fragile than an unsintered
CMC is probably your best bet (maybe too late now.)


I does make a suggestion which you might prefer to adding gums to the glaze:

Subject got me wondering - could one spray the surface with a cheap fabric
spray starch to keep from damaging the glazed surface?


Regards, Peter


PS Do you have any bentonite in your glaze?




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I am not too keen on the spraying stuff onto the glaze after it has been applied. Seems an extra step too far, same with the 3rd firing.


So the bentonite was still making it crawl? You could try using a ball clay instead of some of the kaolin as that I have read can harden the glaze with less clay than kaolin. I would also try sneaking a little bentonite in if at all possible.


If no clay can be added you will have to try something like CMC gum solution that will 'glue' the glaze to the pot and stop it dusting.


Other than that it could be in too thick an application making it crawl and you could get the same white you want with a thinner glaze and some normal clay in the recipe. 


min you beat me to it :D


About sintering I think about 850 should do it.




One last note, I have noticed vinegar hardens glaze too. Nothing to back myself up other than experience. You could try this instead of epsom salts and see if that makes any difference.

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Re. CMC - having gone through the mentally exhausting process of finally getting the glaze to reliably stop crawling, I didn't want to add anything else, ever! Plus I don't have any CMC... but I'm willing to try, if all else fails!


If you live in the UK I'm happy to send you a trial amount. It's certainly something I would try.


BTW if you have calcined all the clay, how well does your glaze suspend?

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I would try a new glaze recipe! If a glaze is that difficult to use, then it's not a good glaze IMHO. Ease of use is an important part of glazing. With the vast number of recipes available on the internet, you should be able to find a glaze that will look good and be easier to use. If 1% bentonite is causing crawling, then it's really not a stable glaze, and you'll probably be fighting it on some level forever. You need some clay in your glaze in order to help keep it suspended and to harden the surface for handling. If you don't have clay, then you need some sort of organic binder. CMC gum would work, but it will increase the water content. You'll have to run some tests to find a balance.

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