Glaze Help Needed!
Posted 02 November 2013 - 07:29 PM
I bought a bag of dry clear glaze, 10 lbs. added 2 tablespoons bentonite, and 110 oz water. The glaze is settling into concrete on the bottom before I even finish mixing it! I am now up to about 10 tbsp. of bentonite. Something is definitely wrong here! Any ideas? Much thanks,
Northern Woods Pottery
Posted 02 November 2013 - 09:31 PM
I would try stirring in a little bit of saturated Epsom salts solution, tiny bit at a time until it behaves. I wouldn't add any more bentonite. (for clear glazes I use macaloid not bentonite as I have had speckling from bentonite, even with the white type) There is an excellent article on flocs, deflocs and thickeners here: http://www.claytimes...eadjusting.html
Posted 02 November 2013 - 11:47 PM
Thank you! I'll go look at that now,
Northern Woods Pottery
Posted 07 November 2013 - 08:06 PM
You could also try adding CMC gum solution, a commercial suspension agent, or glycerin a tablespoon at a time.
Raku, Pit fired, Majolica, and Stoneware ceramic artisit
Posted 09 November 2013 - 05:27 PM
I would stick with epsom salts. The problem with CMC is you often need a fair amount to do the job, and you end up with a glaze with a very high water content, which makes for thin application when dipping. The CMC will also get eaten away by bacteria since it is an organic material, sometimes in a matter of days, and it's difficult to add more to the glaze without first making a solution of it, which means you'll also be adding more water to the glaze and compounding the problem. If you do use it, put a tiny amount of copper carb into the glaze to act as a preservative, like 1/10 of 1%. It shouldn't show up in the glaze. But I'd go with the epsom salts. Cheap and effective.
Kiln Repair Tech
Owner, Neil Estrick Gallery, LLC
Posted 09 November 2013 - 05:51 PM
I say stick with the Bentonite. You have hardly added any. You need about 3% of the weight of the dry material. Should be mixed in water first.Bentonite is a very plastic material. Works to suspend glazes. I use it all the time.If you add Epsom Salts, you are changing the electrolytes at a microscopic level. This causes the molecules to repel each other. Sounds like you don't have enough clay in your glaze Bentonite would solve this. I don't know how to convert pounds to grams in my head, otherwise I would tell you how much to add.
Posted 09 November 2013 - 07:31 PM
I don't know how to convert pounds to grams in my head, otherwise I would tell you how much to add.
Put something like 5 lbs in grams into Google. Regards, Peter
Posted 12 November 2013 - 03:16 PM
The calcium in Calcium Chloride has the same +2 charge as the Magnesium in Magnesium Sulfate (Epsom Salts) but for some reason Calcium Chloride seems to work better in flocculating glazes.
Pete Pinnell thinks so too. http://www.claytimes...eadjusting.html
True, but like Pinnell says:
"The most common flocculants potters use are epsom salts (magnesium sulfate) and calcium chloride, though acids (such as muriatic acid, available from paint stores and pool supply houses) can also be used. Epsom salts work in most instances and can be found at just about any drug store or grocery store. Calcium chloride is a bit stronger (I prefer it), but a little harder to come by."
I think we are getting down to a moot point, both work.
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