Low Expansion Cone 10 Clear Glazes

[LeeS]

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That does sound like spodumene.

Ah ok, I was pretty unsure, it's quite different than most of the other materials I have.

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G0026 is a weird one, doesn't even really look like the same glaze? Maybe the ink is throwing me off.

All the Pier glazes have a noticeable amount more bubbling/orange peel. I'm wondering if it has additional flux (to achieve transparency) that is interacting with the glaze.

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Did you dip them at the same time?  Not sure why the worse clay is a lot better.

Yup, I did all the tests one after another. I also made 250 g batches so everything should have been pretty consistent between tests.

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G0027 seems like the one to go with. I would try reducing the silica and/or alumina and see if that reduces the orange peel texture.  The high SiAl is probably doing a lot for how it fits though so may start crazing again.

Yeah, I think most of my next round of testing is going to be around improving G0027.

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If it does it would be interesting to try your spodumene again and see if adding a little makes it worse or better.

Maybe small additions of spod will help with lowering the expansion without creating this paradoxical effect in a lot of the other higher lithium tests?

[Min]

@LeeS, the glaze you got from Ceramic Arts Monthly is this Lithium B one from Dave Finkelnburg right? I'm still not getting why the crazing was so bad on it with your test unless there is an issue with your spodumene. Wondering if you did the 4321 glaze he is using for this article, variable being the custer versus spodumene amounts, chem of other materials balanced out. If you found less crazing in the 4321 Bernard Leach recipe than the Lithium B recipe then it would indicate to me a spodumene issue. I would figure that out first before taking the time to do other tests with the same batch of spodumene. Even though it doesn't look like a crystal clear glaze it is at the upper end of lithia at 0.20 moles, the highest of all the glazes you tested. Your glaze is acting like its 3110, total opposite of what a lithium spar would do.

[LeeS]

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If you found less crazing in the 4321 Bernard Leach recipe than the Lithium B recipe then it would indicate to me a spodumene issue

That's a good idea, I wasn't sure how to approach figuring that out. I'm going to see if Clay Planet will sell a half-pound of lithium carbonate as well, otherwise I'll order some online.

[LeeS]

I have a bit of an update to a long-lost thread that may be interesting to some of you here. This will probably be a tad light on details because my experiments were interrupted by some personal stuff, so the history is a bit fuzzy.

First off, I discovered quite a serious issue with the clay I was using (Clay Planet Glacia), as detailed here:

https://community.ceramicartsdaily.org/topic/20210-vitrification-and-glaze-fit-issues-with-cone-10-glacia/

Both myself and Clay Planet measured the absorption and it was well above 1%. They provided me with a bag of Pier and that motivated much of the testing in this thread. However, throughout this thread I was still using the Glacia because I had a ton of bisqued work I was still hoping to save, and it served as a good reference that was easier to fit (higher expansion) than Pier.

Apparently this problem only affected the casting slip version of Glacia, and Clay Planet claims they have since corrected it.

Another round of testing had some interesting results:

1. Subbing the spodumene for petalite or lithium carbonate didn't change the results much. The lithium-fluxed glazes still crazed badly.
2. I was able to create a high silica and high alumina, lithium-fluxed glaze that didn't craze using a substantial amount of boron to force it to melt. I thought this would be the one, but it took so much boron (0.3) I was running into issues with bubbling, clouding, and pinholes if the application wasn't perfect.
3. Throughout this process, I found that the Pier porcelain was severely affecting the surface quality of the glaze. Glazes that look great on other bodies would become a bubbly, orange peel mess on Pier.
4. I bought the correct materials for Katz's Mag Gloss and it works pretty well, although it still crazes on Pier.

Per (2), here is the glaze that got the closest. Be warned I'm not proud of this recipe haha:

So, after about ~150 test cups and ~50 different recipes, I was getting pretty sick of everything. I was able to use this glaze for some work that didn't need functional surfaces, and it was good enough for that.

After putting this down for a while I was feeling up to getting back into it, but decided to take a different approach. Even with the Glacia absorption fixed I was not super keen on going down that road again, especially because it's not as transparent or as white as I would like. And the Pier, the porcelain I was hoping to use, had so many bizarre surface quality issues at the it overshadowed the whiteness and translucency.

I decided to formulate my own porcelain based on the standard 25 recipe. That's well underway although I have some questions that are probably best for another thread. Fitting the Clay Planet clays was frustrating enough I figured it might be easier to change the body rather than fight with the glazes. I could obviously try another commercial body, but this sounded like more fun :).

Anyway, this is a bit disjointed, but I hope it's still interesting. Happy to answer questions or provide a bit more detail if anyone is curious.

[Min]

3 hours ago, LeeS said:

First off, I discovered quite a serious issue with the clay I was using (Clay Planet Glacia)

 

3 hours ago, LeeS said:

And the Pier, the porcelain I was hoping to use, had so many bizarre surface quality issues

So, in a nutshell, 2 bodies from ClayPlanet and you had glaze fit problems, absorption problems and quality issues with both? I don't blame you for getting frustrated, time to move on to another body. I can't remember if you have already posted why you are using ^10 vs ^6?

Thanks for the update.

 

[LeeS]

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I can't remember if you have already posted why you are using ^10 vs ^6?

No good reason. I learned at ^10 and that's what the local community centre fires to so that's why I started there. I find it a little more fun because stuff obviously melts better, so there are more options for glazes without requiring a bunch of boron frit.

Honestly it's not a good reason and I should probably just switch to ^6, but I'm enjoying myself and my kiln doesn't have any trouble with it, so I'm not in a hurry.

Thanks again for all your help with my questions Min, you really cleared up a lot of stuff I was unsure of.

[Min]

Kanthal chart below, wire temperature, relative figures for proportion life of elements.  Boron frits are less expensive than replacing elements.  (degrees C/F are reversed)

[Fred Sweet]

1 hour ago, Min said:

Kanthal chart below, wire temperature, relative figures for proportion life of elements.  Boron frits are less expensive than replacing elements.  (degrees C/F are reversed)

Min-

I think your *C and *F values are reversed in your chart.

Regards,

Fred

[Min]

1 hour ago, Fred Sweet said:

Min-

I think your *C and *F values are reversed in your chart.

Regards,

Fred

Yup, I noted that in my post. Chart is from Kanthal.