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48 minutes ago, neilestrick said:

My thought on the bubbly underglazes is that they're in that in-between stage where they are melting more than the others, but not enough to melt out and smooth over. I think stiffening the underglaze could also solve the problem. My concern with adding frit to the underglaze is that it may reduce the porosity after bisque firing, making glazing difficult. I'm going to run some tests both ways with the Speedball red and see what happens.

Maybe, got a bunch of test tiles I have done many ways that led to our fix for what we saw. I am pretty happy with what has worked for over a year now so hopefully it will be useful for someone.  I suspect there are a variety of cause and effects. More research, better for everyone. For us it demonstrably repeated itself when applied very thickly so getting it to occur over and over especially on test tiles  (green, bisque, rebisque after application) was easy. It will be interesting to see what you find. The implication that it could induce crawling is most interesting to me.

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16 hours ago, Babs said:

What is a substitute for Fusion frit in this recipe Min? F524?

F 524 appears as  a strontium barium frit so hard to substitute. 3124 is similar in silica, boron, and alumina  with more calcium instead of strontium and barium.

search Glazy for a chem analysis

Edited by Bill Kielb

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10 hours ago, Bill Kielb said:

F 524 appears as  a strontium barium frit so hard to substitute. 3124 is similar in silica, boron, and alumina  with more calcium instead of strontium and barium.

search Glazy for a chem analysis

Honestly, as a clear glaze, this one is only okay. It can be cloudy, especially if over dark clay or black underglaze. I use it because I can get it premixed, which saves a lot of time for me, and it fits my chosen clay body quite well. It makes a better base glaze than a clear. 

Tony does note that the premixed version available from Plainsman is made with coarser meshes of both Neph Sye and silica than the recipe's originator recommends. I looked into getting a bag of that F 524 frit to test it with the finer mesh of silica. Plainsman will sell you a 50 lb bag, but it was $$$.

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6 hours ago, Callie Beller Diesel said:

Honestly, as a clear glaze, this one is only okay. It can be cloudy, especially if over dark clay or black underglaze. I use it because I can get it premixed, which saves a lot of time for me, and it fits my chosen clay body quite well. It makes a better base glaze than a clear. 

Tony does note that the premixed version available from Plainsman is made with coarser meshes of both Neph Sye and silica than the recipe's originator recommends. I looked into getting a bag of that F 524 frit to test it with the finer mesh of silica. Plainsman will sell you a 50 lb bag, but it was $$$.

I suspect the Barium may have soured the popularity of the frit. Who knows though often pottery is such a small client to the frit industry. Lots of clears out there, didn’t bother to map this out in any glaze software but 7% clay says it likely settles hence the bentonite.

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@Callie Beller Diesel, don't know if you want to try it but I think you could use Ferro 3292(-2) to supply the strontium and forget the barium part of the formula. The barium makes up 0.01 of the formula, it wouldn't be missed I don't think. The Ferro 3292 is available at Tuckers in Ontario and isn't that expensive ($175 for a 50 lb bag). Your ceramic supply place gets Cone Art Kilns from them probably so they might be able to bring the frit in for you, dunno. I redid the recipe using Ferro 3292 (now called 3292-2), on paper it looks okay. Tiny bit of lithium now (0.01) but shouldn't be an issue. COE is the same, LOI is just a tiny bit higher, could get it back down using another frit to supply the lower boron in the 3292 but since the clay is so low in this recipe a bit of gerstley wouldn't hurt. Flux ratio is actually better (slightly) in the sub recipe.

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