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Need Clear Low Fire Glaze Recipe For Red Clay Sgraffito


reggie

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I cant seem to find a good, lead free glaze for sgraffito on red clay.  I would like to mix my own. All the frit recipes I have tried come out cloudy. This could be gasses released in firing causing tiny bubbles. Could be I am not firing high enough.  I used to use a lead base glaze with no problems. Now I am just getting frustrated and feel totally incompetent!

 

Does anyone have a clear glaze for red clay you will share... and also the temperature would be helpful.

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This is my recipe! :) I love it because the ingredients are cheaper than frits. You can see examples in my gallery. :)

 

Shiny clear ^04:

 

Flint/silica: 15

Gerstley borate: 55

EPK: 30

 

This glaze is great. Be sure to bisque to ^04 and fire slowly. It will turn wine colors blue and eat Duncan's EZ petal pink underglaze, but it's good with most everything else. :) I fire my lowfire stuff to ^03, too, so it's a good strong glaze.

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This is my recipe! :) I love it because the ingredients are cheaper than frits. You can see examples in my gallery. :)

 

Shiny clear ^04:

 

Flint/silica: 15

Gerstley borate: 55

EPK: 30

 

This glaze is great. Be sure to bisque to ^04 and fire slowly. It will turn wine colors blue and eat Duncan's EZ petal pink underglaze, but it's good with most everything else. :) I fire my lowfire stuff to ^03, too, so it's a good strong glaze.

 

I used this recipe (Worthington Clear) for a long time in raku and some earthenware work.  I found that the high concentration of GB gave me a lot of grief in the form of variable results.  It especially likes to crawl if applied at all too thick.  

 

Have you had this experience, TheGuineapotter?  If not, do you know what your dry to wet ratio was?  If I remember correctly, you said in the limits thread that you don't mix yourself.

 

I tend toward recipes like the one Neil posted, though I usually use 3195 rather than 3124 for its lower expansion ratio.  Little more pricey because of the frits, but a lower failure rate in my setup more than makes up for it.

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Guest JBaymore

This is my recipe! :) I love it because the ingredients are cheaper than frits. You can see examples in my gallery. :)

 

Shiny clear ^04:

 

Flint/silica: 15

Gerstley borate: 55

EPK: 30

 

This glaze is great. Be sure to bisque to ^04 and fire slowly. It will turn wine colors blue and eat Duncan's EZ petal pink underglaze, but it's good with most everything else. :) I fire my lowfire stuff to ^03, too, so it's a good strong glaze.

 

 

I thought you said here ( http://community.ceramicartsdaily.org/topic/7405-how-much-do-you-stay-within-glaze-limits/?p=70424 ) that you could not afford raw materials, did not have a place to mix them up yourself anyway, and used commercial glazes? :unsure:

 

best,

 

................john

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Those are three ingredients that I purchased FIVE. YEARS. AGO. Fifty pound bags. I had the money to do so, thankfully, and I work slowly, so it has lasted all this time with ease. I mix my clear in my bloody kitchen, and have probably huffed a pound of silica by now because of it. It's been a financial downhill slope since those five years and I don't see things improving. Sorry, but my last two dollars goes to buy my cat food...no raw ingredient is that cheap, anyway.. Would you care to know anything else about my pretty much unbearable life?

 

The glazes I do not mix are the decorative ones I use outside of my illustrations. Those consist of lot more than three cheap ingredients.

 

:(

 

@Tyler: I have come across crawling issues, yes. I just sorta have learned over the years what it does and doesn't prefer--like super thick application, as you said. I also noted that it needs to be mixed really, really thoroughly. Aaand, the stuff on the bottom of the bucket likes to crawl the most. Maybe because the GB is of a higher concentration down there... I wonder if the ratios could be tweaked a little.

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Guineapotter,

 

I appreciate the clarification.  Worthington clear is double trouble for crawling because of the high clay content makes it naturally shrink/crack/and crawl during drying and firing, and the GB causes it as well.  I'll say that I'm a little worried about "the stuff on the bottom of the bucket likes to crawl the most."  That sounds like your clay/flint has settled out.  GB doesn't settle out so much as dissolve partially and encourage gelling of the glaze.

 

Perhaps I'm reading you wrong, but that could cause problems with glaze consistency, stability, and fit.  You've probably got it covered, but I thought I'd add that in case it helps.  Stir that glaze up vigorously and sieve it well before every use, and stir well between dips/brush applications.

 

And don't take John's questions too seriously, I don't think he meant anything by them other than to clarify how you were using the glaze.  It's all good :)

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I think I have had pretty dang good luck with my clear. I usually only have maybe 1-4 kiln sacrifices in the whole load, and that's a pretty dang good firing by any measure. I only had one CATASTROPHIC firing, but that was when I was a rookie and didn't know my poor Fred was firing on 3.5 bloody elements (he has six)! >.<

 

I do not like the implication of being called a liar. That makes for a very angry rodent. >.>

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@Tyler: I have come across crawling issues, yes. I just sorta have learned over the years what it does and doesn't prefer--like super thick application, as you said. I also noted that it needs to be mixed really, really thoroughly. Aaand, the stuff on the bottom of the bucket likes to crawl the most. Maybe because the GB is of a higher concentration down there... I wonder if the ratios could be tweaked a little.

 

Do you want to try a simple experiment to reduce crawling but keep the chemistry exactly the same? Calcine a small bowl of epk next time you do a bisque firing and try subbing part of the regular epk for calcined. If you take out 1/2 the epk the new recipe would be:

 

Silica     15

Gerstly   55

EPK       15

Calcined EPK  12 point 5

 

Less shrinking of the glaze (from the EPK) equals less crawling.

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Guest JBaymore

Min,

 

That actually will increase the alumina and silica content in the fired melt slightly due to the LOI on the calcining process (the weight of H2O will not be there in the weighing process). While it might fix application problems, it might also change the surface of the fired glaze.

 

best,

 

................john

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Worthington clear is double trouble for crawling because of the high clay content makes it naturally shrink/crack/and crawl during drying and firing, and the GB causes it as well.

 

Why does a high clay content mean crawling? I thought it was to do with surface tension in the melt so does that mean clay produces higher surface tension? I also thought GB was a clay.

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@High Bridge Pottery

 

Clay shrinks as it dries, too high a clay content in a glaze formulation means contraction during drying which results in cracks, or during firing, and so crawling, etc.  It's similar to when there's a mismatch between shrinkage rates of slip/underglaze and clay body--kaolin slip will flake off a lot of bodies during drying or later.

 

Gerstley Borate's just a calcium-sodium-borate.  It is very high plasticity, and I believe even throwable in a body, but very very different than a clay.

 

@John

 

I think Min accommodated for the difference in silica and alumina values in her revised recipe.  She's only supplied 12.5% of the original 15% clay, which is about a 17% LOI.  

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Thanks Tyler. I must not have been paying attention while reading digital fire. It says 'Gerstley Borate is also very plastic and thus suspends and hardens glazes as they dry. In fact, few clays have the plasticity and the ability to retain water that GB has.' Only just started using it and I took that sentence to mean it was a clay, it sounded much like bentonite.

 

Must do more reading into B2O3

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I do not like the implication of being called a liar. That makes for a very angry rodent. >.>

 

I don't think you were being called a liar.  Re-read John's comment/question.  Be careful of "flaming" on this forum.  People have been barred for getting too excited about something.  Stay cool and enjoy. You have things to contribute and to learn, like all of us.

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Min,

 

That actually will increase the alumina and silica content in the fired melt slightly due to the LOI on the calcining process (the weight of H2O will not be there in the weighing process). While it might fix application problems, it might also change the surface of the fired glaze.

 

best,

 

................john

 

John,

 

LOI is taken into account by using less calcined EPK.  I plunked the numbers into Insight and they came out okay. (Silica goes from 2.19 to 2.18 and alumina stayed at 0.41, fluxes all the same) Am I missing something here?

 

MIn

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Guinee,Tyler,et al;

I used that Pam and Tim Worthington glaze for a long time when I was doing earthenware. I never had any trouble with it crawling. What I like about Ger Bor is that it doesn't settle out of a glaze like Fritt does. Also it helps the surface to stay hard. Could be your bisque temp, Tyler. I bisque to Cone 07-06. Never had any problem with glaze fit.

TJR.

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I've never met them, but I've definitely seen their work.  I'm not sure that they're in Jonathon's Gallery here in London, maybe in Toronto that I saw their pieces--it would have been August of this year.  Didn't put two and two together that the Worthington in "Worthington clear" is Tim Worthington.  I'm constantly surprised how many great ceramic artists there are in Canada.

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