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tiny spherules in wet glaze


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I am having trouble figuring out what to do about these tiny spheres in my glaze, they are smaller than the sieve I have (think it's 80#) and not sure what is causing them or how to deal with it. It seems the minerals are separating out and hardening into tiny little balls. They will mess up the piece as they don't smooth over or melt well and leave a bumpy pinholed surface. This is my clear but I have seen the same thing in my turquoise glaze as well.

Anyone seen these before and/or know how to deal with them?

1876671779_glazeissue.jpg.fe5725993d979719e0effc73ff6fbb6e.jpg

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Can you rub them out?  I can't tell from the picture, it just looks like pinholes where air escaped after it was dipped.  Do they appear right away?  If the only appear after they're dried is it possible they were soluble salts that crystallized on the surface?  If so you can try to eliminate the soluble ingredients in the glaze

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I can rub them off, not out, they are little solid rocks, not air. They appear after dipping, and after dry, can be brushed/rubbed off. 

the clear is

  • Nepheline Syenite 24%
  • Wollastonite 6.4%
  • Gerstley Borate 16.8%
  • EPK 8% Flint 32.8%
  • Strintium Carbonate 12%
  • Bentontite (optional) 2%

The Turquoise does the same thing, it is

  • Cornwall stone 41%
  • Silica 16.5%
  • Strontium Carbonate 12.5%
  • OM4 ball clay 10%
  • Whiting 10%
  • EPK 5%
  • Lithium Carbonate 5%
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Lithium carbonate and calcium carbonate are both soluble in water. As is the boron from gerstley borate.  Nepheline syenite is also slightly soluble.  So at the end of it, could be a fairly soluble salty mix.  Might just be something you have to rub off after it dries when you use those glazes?  Not sure how to adjust the solubility other than to start subbing frits and such.  Like subbing the whiting for wollastonite, the gerstley for a borosilicate frit, the lithium for a lithium frit or petalite or spodumene, and just go down the line to get things less soluble.  I'm not sure but that sounds like salts crystallizing on the surface to me.

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Pete's Seafoam needs sieving before each glaze session. I get the same little hard balls. Shawnhar they will not go thru a 100# mesh. My glazes sat for 6 weeks before yesterday's session.  I sieved the glaze, using 100 mesh, and the balls appeared. This happens everytime if glazes sit up.  I took a 1/2 cup of glaze and mixed the little balls into it. Then into the microwave for 45 seconds on high, thinking they would dissolve - they did not.

I am thinking it is the Strontium Carb doing this. I have not a solution for the problem.

Pete's Seafoam

  Ferro Frit 3134.............     9.60  
  F-4 Feldspar................    51.30  
  Strontium Carbonate.........    25.50  
  EP Kaolin...................    12.00  
  Copper Carbonate............     5.00  
  Titanium Dioxide............     5.00  
  Glaze Jelly.................     3.00  
                              =========
                                 111.40

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I get something like that in my glazes after they have frozen, but always get strained out after running through an 80 mesh screen. I have come to screening glaze every time I run a glaze load as it saves trouble with little bits of bisque etc that get into the glaze.

 

best,

Pres

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The “little balls” are precipitated crystals of some part of one or more of the glaze ingredients. If the ingredients in the glaze recipe are necessary for the glaze to be successful, one can safely assume that removing the “little balls” will change the glaze in some fashion.   If the balls are not easily dissolved, the remove the balls, dry them, and crush / grind them to a small particle size.  I would use a mortar and pestle, or ball mill, depending on the volume of the “little balls”; after all, the glaze slurry is just a mixture of smaller balls. 

 

The reason fit the formation of the “little balls” could be evaporation of the water, temperature changes, or contamination from pots or tools dipped in the glaze.  A detailed identification of the little balls would be an excellent sophomore lab assignment for analytical chemistry; tedious but not difficult. Most of us don’t need to search for a sophomore chemistry student to join our studio staff. 

LT 

 

As a footnote, if removing the “little balls“ works for your situation, have at it!  Don’t waste time and energy solving a non-problem!

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