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Troubleshooting white glaze, please help


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I've finally ventured to make my own white glaze and now I'm having issues with the oxides reacting to the glaze weirdly or the glaze is simply messed up somehow. I followed the recipe from a studio I had worked in previously and got different results when making it myself. I even had a pottery professor attempt to make the same glaze and she produced a similar result to my own ( the messed up one ). Please let me know if you have any insight. Thank you :D

 

Here is a photo of the messed up glaze and the desired outcome.

IMG_0328.jpeg

portfo1 copy.jpg

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Is this a cone 6 glaze? Reason I ask is because in all likelihood it isn't going to be very durable. Silica and alumina are roughly 1/2 of what the minimum levels should be for a durable glaze. It's odd that it adds up to 136 for the base, almost like someone took a stable gloss glaze with 4 dolomite (that totalled 100) and then loaded it up with 36 more dolomite.

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5 minutes ago, Min said:

Is this a cone 6 glaze? Reason I ask is because in all likelihood it isn't going to be very durable. Silica and alumina are roughly 1/2 of what the minimum levels should be for a durable glaze. It's odd that it adds up to 136 for the base, almost like someone took a stable gloss glaze with 4 dolomite (that totalled 100) and then loaded it up with 36 more dolomite.

Yes it is cone 6. Do you recommend doubling the silica and alumina then? 

 

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5 minutes ago, dhPotter said:

Neph Sy has a lot less Silica than Minspar 200. Try using Minspar 200 for F4

Silica and alumina levels are too low with either Minspar 200 or the original F4  I agree with subbing Minspar for the F4 and not using Nepheline Syenite but it still won't make a durable glaze.

495055889_ScreenShot2021-05-05at1_26_50PM.png.98629d4910ba5a6202a3857099d4737d.png

Edited by Min
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2 hours ago, offmenu said:

. I followed the recipe from a studio I had worked in previously and got different results when making it myself. I even had a pottery professor attempt to make the same glaze and she produced a similar result to my own ( the messed up one ). Please let me know if you have any insight. Thank you :D

It’s hard to tell from your picture but the top glaze seems clear and glossy and the bottom seems more matte and potentially colored slightly blue. The only colorant being zircopax. What is the desired look?

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4 minutes ago, Bill Kielb said:

It’s hard to tell from your picture but the top glaze seems clear and glossy and the bottom seems more matte and potentially colored slightly blue. The only colorant being zircopax. What is the desired look?

Here's a better example with white clay, the speckled makes it appear more matte.

Ideally I'd actually prefer a matte white glaze but this recipe worked well so wanted to stick with it until I'm able to learn how to achieve that.

cup1.2.jpg

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5 minutes ago, offmenu said:

The original was a glossy white (second picture added)

Is it the picture, the second does not look very glossy or white. Are the decorations to be glazed over with this glaze?

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1 minute ago, Bill Kielb said:

Is it the picture, the second does not look very glossy or white. Are the decorations to be glazed over with this glaze?

Here's more natural light to show the glossiness. They are etched in with oxides over the glaze.

cup4.jpg

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37 minutes ago, offmenu said:

Here's more natural light to show the glossiness. They are etched in with oxides over the glaze.

 

Got it, neither of the top two show signs that zircopax is truly in there, they are near clear.  I would check that the zircopax was truly added in the right amount or the zircopax used was not contaminated for sure. As far as cone six you have 0.15 boron which is oddly spot on for cone six  but you also have relatively low alumina. You also have a lower amount of clay in this recipe. Clay will help the glaze stay suspended which means there likely would not be a need for bentonite which really does nothing for the chemistry except help keep it suspended. Neph sy actually gets you more alumina than minspar or Kona.  The Dolomite number looks extremely large ....... and the base recipe adds up to 136%!

Can you re-copy this, it appears there is a typo in the recipe for sure so rather than trying to modify this one, maybe double check the proportions including if the base  recipe (Top one) was for a 2000 g recipe. It’s really hard to speculate what this should be.

Edited by Bill Kielb
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I’d put this recipe down and back away slowly. It’s  pretty broken. It will not be a good beginner project to fix this one. The flux ratio is also way out to lunch, and with such a high LOI, I’m not surprised your surface decoration is breaking and running like that. I would suggest that whatever’s in the bucket at your community studio is not what was written on the bucket label.

If you want a durable base glaze that doesn’t move much, pick one of the ones from digitalfire and add your 8%  Zircopax to it. You may have to adjust for clay body fit, but that’s a smaller project than fixing this one would be.

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7 minutes ago, Callie Beller Diesel said:

Min’s ahead of you on that.

Didn’t really notice - thanks! Probably good to know if the recipe was for two thousand grams though.

Edited by Bill Kielb
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1 hour ago, offmenu said:

The original was a glossy white (second picture added)

Okay, so if all you need is a glossy white you could take your recipe and subtract 36 dolomite from it. This is the third recipe in the green boxes I posted above, just replace the F4 with Minspar 200. It looks like it should fire to a durable white gloss at cone 6 with the reduced dolomite. Boron is higher than it needs to be but should still be okay. I would suggest mixing up 100 grams of the base (you don't need the bentonite in there) then adding 8 zircopax, dip a test tile that you have some of your underglaze/slip/oxides on or overtop, depending on how you normally do it. Now add another 2 zircopax and dip another tile. Repeat this one more time to have a total of 12 zircopax. Fire the test samples and see how they colourants show and test for glaze fit.

Other way you could go is to take an existing clear glaze that fits your clay and add zircopax to it. If you have a coloured clear glaze just remove the colourants from it and use that as the base glaze.

If you want a dolomite matte the simplest way to get the gloss/matte sheen you like is to blend a dolomite matte with a clear glaze. I like this one and this one, good directions on how to go about doing this in the links also. The Ferro frit 3249 is expensive but the melt is better with that second recipe.

edit: it's 10 posts up from this one if you need it @Bill Kielb

Edited by Min
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26 minutes ago, Min said:

edit: it's 10 posts up from this one if you need it @Bill Kielb

I am lost on this. I am Just not sure if her recipe was for 2000 g originally and if this was normalized to represent that. I am presently working though so could be something I am missing above. Just don’t have time to sort through whatever that might be right now.

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15 hours ago, Min said:

Okay, so if all you need is a glossy white you could take your recipe and subtract 36 dolomite from it. This is the third recipe in the green boxes I posted above, just replace the F4 with Minspar 200. It looks like it should fire to a durable white gloss at cone 6 with the reduced dolomite. Boron is higher than it needs to be but should still be okay. I would suggest mixing up 100 grams of the base (you don't need the bentonite in there) then adding 8 zircopax, dip a test tile that you have some of your underglaze/slip/oxides on or overtop, depending on how you normally do it. Now add another 2 zircopax and dip another tile. Repeat this one more time to have a total of 12 zircopax. Fire the test samples and see how they colourants show and test for glaze fit.

Other way you could go is to take an existing clear glaze that fits your clay and add zircopax to it. If you have a coloured clear glaze just remove the colourants from it and use that as the base glaze.

If you want a dolomite matte the simplest way to get the gloss/matte sheen you like is to blend a dolomite matte with a clear glaze. I like this one and this one, good directions on how to go about doing this in the links also. The Ferro frit 3249 is expensive but the melt is better with that second recipe.

edit: it's 10 posts up from this one if you need it @Bill Kielb

Thank you for your help! I'm going to give this a try.

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