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Deflocculating an overly flocculated glaze


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#1 VermontSarah

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Posted 12 June 2013 - 09:32 AM

I need help. I am pretty sure I have overly flocculated glazes because they don't settle, look like gel, don't dry on a test piece of bisque, and have a lot of lithium and strontium in them. I've tested the specifc gravity and it is quite low meaning I'm sure I've added too much water to try to un-gel them at some point. I'm leaving them open to evaporate out some water now. The glazes are Steven Hill Water Color Green and Water Color Blue. I also have the same problem with Wright's Water Blue which I think has some similar ingredients. The problem is, no amount of Darvan 7 seems to help. That stuff gets expensive too. I have some fairly large batches so I don't want to throw them out, and plus, if I start over I'm afraid I'll have the same problem over time. In the future I will make much small batches. Any suggestions? Thanks in advance.

#2 JLowes

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Posted 12 June 2013 - 02:17 PM

Hello VermontSarah,

I have made Watercolor Green (Watercolor Blue is similar) and mine is water thin, so something may have gone wrong for one of us. I spray my glazes, and mixed mine to the consistency I saw during a Steven Hill workshop, and they work well thin.

I like this video by John Britt discussing flocculation and deflocculation, and some of the things you can try with a small sample to see if you can make it workable:

http://www.youtube.c...h?v=fpQns05RdVU

For comparison, the recipe I use is as follows for 1000 grams (I never mix much at a time):

Watercolor Green

Cone6
Batch Weight1000.0
Ingredient Wt (Grams)

Custer Feldspar 442.4
Flint 156.7
Lithium Carbonate 36.9
FRIT 3124 46.1
Whiting 147.5
Strontium Carbonate 69.1
Copper Carbonate 73.7
Bentonite 27.6
Totals 1000.00

If you divide the numbers above by ten you will have a percentage recipe.

I suspect that there is something in the batching that is causing your problem. Is your spar different than the one above?

I also looked up a recipe for the Wright's Water Blue, and it appears to be frit based, so it would tend to hard pan on the bottom if the Bentonite can't keep it in suspension.

Wright’s Water Blue Glaze
Cone 1-6
Oxidation
Glaze Material
Percentage
Lithium Carbonate 3%
Strontium Carbonate 9
Frit 3110 59
Edgar Plastic Kaolin 12
Flint 17
Total 100%
Add: Bentonite 2%
Copper Carbonate 5%


John


#3 VermontSarah

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Posted 12 June 2013 - 03:11 PM

Thanks, John. My batches are pretty large, and therefore old, and I think they have changed over time. I have studied the John Britt video over and over and no amount of Darvan seems to help. Do you ever check your specific gravity?

By the way, I spray everything too. I generally like to use glazes as thick as I can get them through the spray gun, because I single-fire and any extra water is hard on the raw pots. I'll keep trying and let you know.

Since you've used Steven Hill's glazes, let me ask you, do you have much experience with Hannah's Fake Blue Ash? I can rarely get it to fire blue. It over-crystalizes and I just get brown or bronze with maybe a little edge of cobalt. I've tried that glaze so many different ways I should have given up by now, but I'm stubborn.

I took Steven's workshop last May in Independence. Sadly, he is not available by email for these questions.




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