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CMC is an organic gum, and will get eaten up by bacteria very quickly. You have to use a preservative, such as copper carbonate (0.25%) to keep it working. VeeGum-T is not an organic gum, but rather a member of the smectite family, like bentonite. Both can be used in glazes as suspension agents and hardeners, for making glazes brushable. A combination of the two is ideal, although CMC alone works very well and is much less expensive than VGT. Both must be well hydrated before being used. They should not be added directly to the glaze. Veegum-T is also used as a plasticizer in clay bodies like porcelains. VGT is quite expensive, and can make up 25% of the cost of the body even though it's only 2% of the recipe.

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Magma works really well. I use it in a glaze that really hardpans and it suspends the glaze exceptionally well. I mix up a bit with copper carb and keep it in a container,  it goes like disgusting goop when concentrated like this but it works. The glaze I use it in is one I don't use often, even after sitting for months it doesn't hardpan.

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21 hours ago, docweathers said:

Thanks for the scoop. Interesting, I've had CMC solutions setting around for years and never had any rot.  Maybe it's just too cold where I live in Washington for them little critters to grow.

decompose would have been a better, less dramatic, term to use :)

I'm a fan of Veegum T as a nice addition to certain stoneware clay bodies even at 1%. I'm no clay tech but the difference is obvious.

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On 11/1/2018 at 9:53 AM, Min said:

Magma works really well. I use it in a glaze that really hardpans and it suspends the glaze exceptionally well. I mix up a bit with copper carb and keep it in a container,  it goes like disgusting goop when concentrated like this but it works. The glaze I use it in is one I don't use often, even after sitting for months it doesn't hardpan.

Did you put a preservative in also?

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5 hours ago, Rae Reich said:

Did you put a preservative in also?

Yup, copper carbonate as a preservative. It will rot fairly fast without it. 

4 hours ago, docweathers said:

never heard of magma as a glaze component before. I think of it as something in volcanoes. Where you buy the stuff?

I ordered mine from Brackers, info on how much to use for what type of glaze, copper carbonate amounts etc here.

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I have mentioned magma here for years-its sold at various places like the big ceramic store online.

It holds settling glazes in suspension better than any other thing I have used in my brief 45 year history with ceramics glazes .

Doc I cannot tell you how it brushes as I mostly never Brush glazes other than to use a few of my high fire glazes as underglazes before pouring or dipping on top of them.I assume you are asking about brushing type commercial glaze when brushing and I do not use them ever-I mean ever-I do nit own any.

Magma will keep the most setting glaze you have in suspension-you add a small amount of copper to keep it from spoiling. As Min says it turns into a snot like substance in a jar but mixes easily with a shot of hot water into a glaze.

it makes epson salts and bentonite about obsolete for suspension agents.

Edited by Mark C.

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1 hour ago, Mark C. said:

I assume you are asking about brushing type commercial glaze when brushing and I do not use them ever-I mean ever-I do nit own any.

 

I've never used a commercial glaze. My pigsty would not be nearly as interesting if I didn't have  such things to splatter on the walls and floor.. Mixing my own  glaze is part of the exploration

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