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Biglou13

Snowflake crackle CAD

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CAUTION newB issues to follow.

 

I tried the #8 blue from here.(local studio owner made it )

http://ceramicartsdaily.org/ceramic-glaze-recipes/mid-range-glaze-recipes/crazy-beautiful-crazing-uncovering-the-mysteries-of-snowflake-crackle-glazes/

 

I got crawling and it is beautiful. See pics

I' d like to do 2 things with this

1. Repeat it/ and with different colors

2. Fix it so it looks like sample.

 

When delving into glaze formulas etc... I get that same headache I used to get in chemistry class...

 

I've Re read the article many times including further research into cte, clay and glaze fit, along with Lot of new glaze vocabulary.

See. http://ceramicartsdaily.org/ceramic-glaze-recipes/glaze-chemistry-ceramic-glaze-recipes-2/technofile-glaze-fit/

 

Info :

 

the piece In picture is mostly standard 266, mixed with studio recovery clay, with added fine ,medium and coarse grit. Unknown cte.

As far as I know the (I didn't mix it) the recipe is true to formula.

 

Issues and questions:

 

Why did it crawl vs. craze? How do fix?

Mag carbonate off in recipe?

Does firing schedule greatly affect this? Eg ramp hold cool times.

Is there a big difference between cone 6 and cone 7 in how this glaze looks?

Does standard 266 or Laguna 900/ WAC-628, cte compare high water earthen red or brownstone?

How much Epsom salt to prevent deflocculation?

Picture 2 shows a drip. It is approx. 1/4 inch from clay surface. It is dangerously close to dripping off. Since current formula crawls (less tension) and not craze can I get away with thinner glaze on bottom?

Since crawl has less tension, can I get away with glazing small test plates one side?

(I understand testing is king, but would like some input)

 

Next testing:

 

Try #4 formula. With unadulterated clay.

Test with both bowl like form , and one sided test plates.

Use current recipe with unadulterated clay. See if results change.

 

Thanks in advance for and advice answers or comments.

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post-25544-136469162168_thumb.jpg

post-25544-136469159249_thumb.jpg

post-25544-136469162168_thumb.jpg

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this glaze seperated into a crawling glaze early into firing, most likely there is a high percentage of talk in the glaze. Since it softened, it is high in flux as well to counteract the dry qualities of the talk.

 

No way to fix this unless you can provide a recipe, seems pretty stable, use it on sculptural pieces or as a top coat of glaze on top of a different glaze to be an added color effect.

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See above link for credit

 

Snowmflakemcrackle #8

Mg carb. 3.94

Ferro frit. 3124 7.41

Neph Sy. 82.74

Om-4. 5.91

 

Plus 2% bentonite

Blue .066 cobalt carbonate

 

Article states original recipe was designed to crawl. But then altered to craze.. I'd like to fix it so I can have 2 glazes with one with craze one with crawl.

 

 

Thanks for the info

 

Corrected lol

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Just a couple of thoughts . . .

 

Standard 266 has a ton of red iron oxide and manganese dioxide in the clay body; in Britt's article, he states that adding coloring oxides (which could include RIO and manganese dioxide from the clay body) resulted in reducing the level of crackling in the glaze -- the COE of the oxides countered the COE of the glaze. You might want to try the glaze recipe on a more neutral clay body that is not loaded with colorants. And, you might want to try a test of just the base glaze (for each of the recipes) before testing with colorants.

 

What is your glaze thickness . . . Britt's article mentions a glaze thickness of between 1/8 and 1/4 inches (my guess is John leans toward the 1/4 inch). The snowflake crackle occurs from both vertical and an horizontal crazing. If you did not apply the glaze thickly . . . then it will not form the various layers that Britt achieves. Thickness may be the reason you got a crawl instead of a craze.

 

Testing on tiles should be okay . . . but try not to fire them flat; try leaning so you can get sense of how the glaze moves.

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your glaze does craze and crawl. inside the crawls there are micro fissures in the glaze, as the glaze is only semi transparent ... you won't see them that much.

 

Also this glaze is wonky, It is more of a slip since it is devoid of silica. whatever ferry fruit is, is where your colorants come from since magnesium carb is talc without the silica and twice as expensive for the same thing. and the rest is just ball clay and a low fire flux. the only way to clear this glaze up some to see your crazing in the glaze is to add glass formers (silica) you can do this by substituting mag carb for talc since it's actually an inverse ratio ... lemme see if I can do the math ... 43% of mag carb is comprised of mag oxide, talc is comprised of 31% mag ox ... with that math ... you would be looking somewhere right around 4.7% talc and you would then have a glass former in the glaze.

 

I have a feeling someone in your area is doing base line blends since there is no colorant, and ferry fruit is either a % of another glaze that person uses ... or it's a mason stain which could also add to the opacity and letting you not see as much of the crazing. if you test the glaze with the following recipe you may be able to do the same thing, with more consistant results.

 

Talc 5%

Neph Sy 82%

ball clay 6%

cobalt carb 1%

 

I wouldn't know if crazing will be evident due to the mystery ingredient in your original recipe provided to you ... but it should be close. if it's not present, you can always up the ball clay to 11% and see if the shrinkage in cooling will be more evident.

 

I'm also a fan of rutile ... add 1% and you will probably get some nice milky highlights at the tops of those crawled dimples.

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Yeah, if that frit is used ... you can discard it from the recipe, the borosilicate frits help prevents crazing. so yeah, avoid most frits and avoid borax in that glaze. use the substitution recipe, and if it doesn't melt enough since just discarding it is a decent amount of flux ... up the neph sy to 89%, but my advice still applies.

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I blame most of your issue on your clay body. 266 does crazy things to most glazes, and this glaze is very odd to begin with. I'd try a more typical clay body before altering the glaze. I'd leave the frit in. It's bringing that glaze down to cone 5.

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It's bringing that glaze down to cone 5.

 

 

the frit and the neph sy do that, being as how it is over 4/5ths low fire flux, that glaze will melt fully to a liquid at cone 01 ... easily a liquid at 06. Being as how only the ball clay and talc pushes the glaze temp up, hoping that it does reach cone 5 for stability is a pipe dream. Again, he's looking for crazing, adding a borosilicate frit will help prevent crazing ... so ... yeah.

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It's bringing that glaze down to cone 5.

 

 

the frit and the neph sy do that, being as how it is over 4/5ths low fire flux, that glaze will melt fully to a liquid at cone 01 ... easily a liquid at 06. Being as how only the ball clay and talc pushes the glaze temp up, hoping that it does reach cone 5 for stability is a pipe dream. Again, he's looking for crazing, adding a borosilicate frit will help prevent crazing ... so ... yeah.

 

 

I do not consider neph sy to be a low fire flux. If it was fully a liquid at cone 01, it would be on the shelf by 6.

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I do not consider neph sy to be a low fire flux. If it was fully a liquid at cone 01, it would be on the shelf by 6.

 

 

Funny you should say that ... look at those original photos closer, it just about was on the shelf. You don't need to consider it a low fire flux, with a melting point of around 2000 degrees, that his hardly high fire, as FF 3124 has a melting point of around 1800 to 2000 ... 8% missing won't hurt that recipe and missing the ... what is it Boric Oxide? ... might get him the results he wants.

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I do not consider neph sy to be a low fire flux. If it was fully a liquid at cone 01, it would be on the shelf by 6.

 

 

Funny you should say that ... look at those original photos closer, it just about was on the shelf. You don't need to consider it a low fire flux, with a melting point of around 2000 degrees, that his hardly high fire, as FF 3124 has a melting point of around 1800 to 2000 ... 8% missing won't hurt that recipe and missing the ... what is it Boric Oxide? ... might get him the results he wants.

 

 

 

1. A glaze that is fully liquid at cone 01 wouldn't still be on the pot at cone 6. It would be a large puddle on the shelf.

 

2. By high fire flux I mean it is commonly used as a flux at higher temperatures. It has little to do with its actual melting point. Most fluxes melt at lower temperatures than the glazes they are used in. That's the nature of fluxes. They bring down the melting point of the silica to a useable temperature.

 

3. Ferro 3124 has a melting point of 1700. So it's obviously doing something to that glaze. You can't just take out 8% of an ingredient and not expect it to affect the melt of the glaze. 2%, fine. But not 8%. Take out the boron if you must, but reformulate to maintain the rest. That said, the boron content of the glaze is very low, about 1%, so taking it out should have little effect.

 

This is why I love this forum.laugh.gif

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CAUTION newB issues to follow.

 

I tried the #8 blue from here.(local studio owner made it )

http://ceramicartsda...crackle-glazes/

 

I got crawling and it is beautiful. See pics

I' d like to do 2 things with this

1. Repeat it/ and with different colors

2. Fix it so it looks like sample.

 

When delving into glaze formulas etc... I get that same headache I used to get in chemistry class...

 

I've Re read the article many times including further research into cte, clay and glaze fit, along with Lot of new glaze vocabulary.

See. http://ceramicartsda...file-glaze-fit/

 

Info :

 

the piece In picture is mostly standard 266, mixed with studio recovery clay, with added fine ,medium and coarse grit. Unknown cte.

As far as I know the (I didn't mix it) the recipe is true to formula.

 

Issues and questions:

 

Why did it crawl vs. craze? How do fix?

Mag carbonate off in recipe?

Does firing schedule greatly affect this? Eg ramp hold cool times.

Is there a big difference between cone 6 and cone 7 in how this glaze looks?

Does standard 266 or Laguna 900/ WAC-628, cte compare high water earthen red or brownstone?

How much Epsom salt to prevent deflocculation?

Picture 2 shows a drip. It is approx. 1/4 inch from clay surface. It is dangerously close to dripping off. Since current formula crawls (less tension) and not craze can I get away with thinner glaze on bottom?

Since crawl has less tension, can I get away with glazing small test plates one side?

(I understand testing is king, but would like some input)

 

Next testing:

 

Try #4 formula. With unadulterated clay.

Test with both bowl like form , and one sided test plates.

Use current recipe with unadulterated clay. See if results change.

 

Thanks in advance for and advice answers or comments.

 

 

The crawling in your pictures was Great! I mixed up the Snowflake Crackle #4 some months ago. I tested it on smooth white clay and a brown clay with a bit of grit/sand in it. It was positively perfect on the smooth white clay (of course it did not show the crackles to their best) on the brown slightly gritty clay it did not look as nice, and it was very rough. I found some smooth brown clay and tried the glaze on that. But I have to say it is hard to apply, so the bowl was very lumpy. I tried again, and thinned the glaze and brushed it on....the crackles were very nice, on a smooth brown clay, but it was still sort of lumpy. So, I will try this again and thin it alot and spray that glaze and see what happens! The #4 recipe was

 

 

talc 7.86

FF 3124 5.77

Neph Sy 86.37

 

I did not add colorant. Although I wanted to!

 

This led me to the conclusion that clay body has a great deal to do with this glaze (as with most glazes) and application is a key part of the process. Oh and I fire to cone 6, oxidation

 

Roberta

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Ty for the pics.

 

I'll try #4 formula also. Looks like its working . How thick did you apply glaze?

 

 

 

That is the problem I am having. It's like obleck. What is the term? it flocculates?? Settles to the bottom? So, when the article said it needs to be thick, that was my first challenge. It sort of clumps. So the second time I applied, I thinned the glaze a great deal and put numerous coats on the picture you see. But it still clumped up. Soooooo the next time I use it I will thin it a LOT and try to spray it on. Let me know if anyone has better ideas. If we can figure it out, it will be such a pretty glaze. Not functional I am assuming because of the crackles, but it will be beautiful. thanks for your help with the pictures Biglou

 

 

Roberta.

 

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