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High Bridge Pottery

A Few Glaze Problems, Drying To Slow... Not Enough Suspension.

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Ok, well I had a few questions but don't seem to have put one recipe into my glaze database or I am just too tired to decipher my own work.

 

One recipe I do have goes as follows.

 

Soda Feldspar 51

Potash Feldspar 36.7

Quartz 25.5

Dolomite White 2

Whiting 18.9

China clay 2.6

Ball Clay 9.2

Iron Oxide 11

 

Nice looking glaze, but after 3 hours it is nearly rock solid on the bottom. I have bentonite, so can I add this to my glaze if I mix it with water first? How much would be a good amount for this recipe?

 

I used to put some plaster of paris in my glazes to aid suspension and it seems to work quite well. Anybody have an opinion on which one they prefer or their favorite suspension agent?

 

 

 

The other recipe I have just takes forever to dry!! I am talking about 5 minutes a pot before I can handle it :( Sorry I can't post the recipe but I will add it when I quickly pop into the studio later on and can find my glaze book. It is just hard to glaze them and not touch any glazed bit until it is dry.

 

Edit : Recipe

Soda Feldspar 10

Cornish Stone 30

Quartz 10

Dolomite White 10.5

Whiting 10.5

China Clay 25

Tin Oxide 2.7

Zinc Oxide 4

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That.... Does not add up to 100.  ;)

 

But just doing some mental comparisons, way more feldspathic components than clays. It will definitely tend to settle/pan out.

 

From what I've read & the few glazes I've made, adding about something bentonite will help. 4-5% is a good starting point. It's better to mix it in with some dry components to avoid clumping, but if you can't then mixing it with water is definitely the way to go.

 

John Britt has a great Youtube on this that is posted around here pretty frequently:

 

It addresses the use of bentonite, and the issue of glazes that take a long time to dry.

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Is her 2nd glaze OVER flocculated?   Why won't it dry and why add epsom salts to that problem?  I understand adding ES to the hard paned glaze.b

Yeah, going by what John says in the video, if a glaze is taking a while to dry, it is flocculated. His solution was the Darvan 811, or sodium silicate.

 

I am not an expert, just parroting what I heard.

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The reason this glaze is settling badly is because it's low in clay. Bentonote is needed to keep it suspended, and the eposom salts will help everuthing stick to the bentonite.

 

The reason the other glaze is drying slowly is probably because it's high in clay. Clay holds onto water more than other glaze ingredients. I've got a couple glazes like that too. Just gotta be patient, or a little deflocculating, but be careful you don't go too far or it'll settle out.

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Is her 2nd glaze OVER flocculated?   Why won't it dry and why add epsom salts to that problem?  I understand adding ES to the hard paned glaze.b

 

That advice was posted before I had edited the second recipe into the topic. Thanks for the tips, I think I will just have to be patient or try and substitute out the china clay for something else.. Going to add some bentonite and epsom salts (if I can find epsom salts) to my glaze tomorrow,

 

Hey, I never knew I was a woman  :lol: maybe that is where I am going wrong

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 epsom salts (if I can find epsom salts)

 

Co-op and Lloyds pharmacys didn't stock ES, but local independant did, when I tried last week.

 

Often in supermarkets   magnesium sulphate, bakingtuff or among the soaps, shampoos etc, a soak for sore muscles as well as a laxative I believe.

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Found 200g Epsom Salts in Boots for £1.49 :D

 

Time to relieve my glaze of occasional constipation, only problem is I cant remember if I did 20x the recipe or 30x to fill the bucket. I will assume 20 and then see how that works out, better to let myself add more if need be.

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Yep, bentonite and Epsom salts....that's the ticket.  Many recipes will have 2 or 3% bentonite already added in.  But I have added it to glazes that really settle.  I am pretty sure I added Epsom salts to my bucket o slip also. 

 

Roberta

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Try mixing in some plain white vinegar, about 1/4 cup for a 5 gallon bucket. This has worked for me with a glaze that persistently settles out and does not appear to affect the glaze results. Eventually, the glaze will begin to settle out again at which time I add some more vinegar. Inexpensive and readily available. If it doesn't work, you haven't lost anything but a little time. If you don't want to try it with the entire bucket, take out a pint and experiment.

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I am following with interest, I have watched the Britt video and while it's clear for a glaze that deadpan , it's not clear for a glaze that just thickens...i added sodium silicate and it gets thicker. I am dumbfounded. I read somewhere then when it thickens so much you can add more water, but Britt says it's a no no. I have tried Epsom salts too and the glaze already has 3% bentonite ...and it thickens ...Help?

clay lover likes this

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