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missholly

bubbles in glaze?

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i just tested 4 glazes. all the same base with different colorants.

fired to 06.

 

theres a patch pretty much all around the center where the glaze bubbled on 3 of the glazes.

 

the test tile was laid flat, not tilted to show any kind of flow.

 

anyone have any idea of whats going on?

 

photo2copy2.jpg

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Chris is right, with out seeing the recipe it's harder to tell what's going on here.

 

 

This is such a complex problem that can be caused by about a dozen problems. I can recommend a book that can help you troubleshoot and hopefully narrow down which of the things you've done that has resulted in the results you have here. I rented this book from my library for free and have since decided to purchase it as a reference in my studio.

 

The Potter's Studio

Clay &

Glaze

Handbook

 

Jeff Zamek

 

2009, Quarry Books

 

A great book that discusses your problem in great length in a trouble shooting format.

 

 

Best of luck,

Ben

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^06

 

silica 2

3134 89.5

EPK 8.5

bentonite 2

vgum 1 tsp

 

 

colorants

 

blue

 

6% rutile

3% copper carb

1.5 cobalt carb

-------------------------------

purple

 

6% mang diox

-------------------------------

red

 

10% red stain

------------------------------

green/gray

 

2% nickle ox

-------------------------------

 

 

 

they grey/green i did test once before and it came out great. the only thing i did differently this time was used 1tsp of powdered vgum instead of the weird snotty like consistency vgum. (i dont know if theres a difference) and these glazes were brushed on super thick, not dipped.

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Been there, and its no fun. Working with the folks who made my clay, they figured out my crater/blister issues by doing a lot of testing

and found out that it

was an incompatibility issue with the commercial glaze I was using and the clay body. I now just avoid those glazes and have not had any blistering.

I hope you can figure out why you are

having problems.

Juli

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That really is an issue most of us go through.

One hint that might help is to use less silicate in your slip if you are the one that is making the bisque.

Too much silicate makes it harder for some paints to adhere, even acrylics!

Make sure you use the right amount of silicate.

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where was the piece placed in the kiln? In years past I was having some pieces blister on occasion and for me it was a result of turning up the gas (temp) too quickly. Was your piece right under the damper and did you turn the heat up really fast on one or more occasions during the firing?

 

Giving it enough time to mature or even out is also important to consider and may be a part of the problem you are experiencing.

 

Good luck, study your notes from the firing and then read, read, read.

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where was the piece placed in the kiln? In years past I was having some pieces blister on occasion and for me it was a result of turning up the gas (temp) too quickly. Was your piece right under the damper and did you turn the heat up really fast on one or more occasions during the firing?

 

Giving it enough time to mature or even out is also important to consider and may be a part of the problem you are experiencing.

 

Good luck, study your notes from the firing and then read, read, read.

 

 

 

the piece was at the top of the kiln. it was not under the damper. i fired as i always do, (5 switches, one switch per 30-45 minutes or so)

 

whats weird is, i fired three of the glazes again on bisque pieces that stood up, this time, the bubbles were only on the back and far less.

its back to class for me tommorrow, so ill be asking my teacher!

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The most common basic low fire glaze is 90% 3124 and 10% EPK. Your recipe is a slight variation of that. Frit 3134 does not melt out well in that formula. Switch to Frit 3124 and it should work.

 

 

so, just 90% 3124 and 10% epk, then colorants?

is this a gloss base?

 

thats what im trying to do is get a good base so i can add colorants from there.

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The most common basic low fire glaze is 90% 3124 and 10% EPK. Your recipe is a slight variation of that. Frit 3134 does not melt out well in that formula. Switch to Frit 3124 and it should work.

 

 

so, just 90% 3124 and 10% epk, then colorants?

is this a gloss base?

 

thats what im trying to do is get a good base so i can add colorants from there.

 

 

Yep. Piece of cake glossy clear glaze. If you want to make it opaque, add 10-12% zircopax or 5% tin oxide.

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Yep. Piece of cake glossy clear glaze. If you want to make it opaque, add 10-12% zircopax or 5% tin oxide.

 

 

 

 

awesome, thanks so much!

itll be nice to not have to deal with so many chemicals and measurements!

 

wish me luck!

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