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LeeS

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  1. Thanks a lot for sharing Mark. I'll definitely consider that Laguna option if this project doesn't work out. The recipe looks like a fairly standard 25 porcelain. I started at a pretty similar point, but because it's a casting body I was able to use all kaolin without worrying too much about plasticity. The biggest adventure has been the feldspar. I've had very different results with different feldspars... Well, mostly Custer just doesn't flux that well and you need far closer to 25% compared to the other types. Yeah I much prefer Darvan to sodium silicate. It's much easier to use as
  2. I couldn't find anything on their website with that name. It seems the only ^10 porcelain casting slips they list are 500L and Toshi? I haven't tried anything from Laguna though. I considered exploring their stuff before embarking on this experiment but making my own body sounded more fun :). That'll be my next stop if this turns into a failure. I would love to see them! No rush of course. Yeah I'm developing this without really worrying about cost, because it's just a hobby and I don't go through enough clay for it to really matter. Obviously your production world is a lot d
  3. I've heard of it; and wow is it tempting! You're right that it's another rabbit hole though and I should probably get out of this one first :D.
  4. Very quick update. I got a fancy new (well, new to me) scale and ran significantly more accurate absorption tests, then compiled the data: Nothing surprising here, just happy I was able to build some confidence in these numbers. B0013/B0015/B0019 are all very clean and translucent. Getting rid of Custer feldspar helped noticeably, both with vitrification and translucency. Swapping EPK for Grolleg would probably help more still, but I'm happy with where it's at and the diversity of clays will hopefully mitigate batch-to-batch variation. I also made up a much larger batch of
  5. Thanks Min, very interesting. I was inspired by Hansen's tests, but didn't read the details of the test process too carefully. His reasoning for thicker tiles seems sound. I'm curious if anyone knows why you should test with a different sample each time? I have a pretty small kiln so that would be a huge pain. I guess once I've moderately confident in my clay body and glaze it could be worth it.
  6. I actually left out that I slowly ramped up the test conditions until I got some sort of result. After boiling water, I started at 300F, then tried 350F, then 400F. I found if I'm not at least somewhat aggressive with the testing, my test cups will appear fine but when I glaze something larger it will craze. This is a great idea, I'll definitely give it a shot next firing. In general I think a thicker glaze layer on my tests would help suss out issues. I glazed this round "properly" like I would for finished ware, but that doesn't give me quite as much data about more marginal fit issu
  7. I was able to test B0019 and a series of glazes. The results are somewhat encouraging, although I definitely have another firing or two before I'll be able to settle on a formulation. At ^10, test results and recipe: B0019 (15% feldspar) -- 0% absorption (1.6% absorption at ^8), 10% shrinkage Silica 25 EPK 30 Grolleg Kaolin 30 Minspar 200 7 Nepheline Syenite 8 VeeGum T + 0.75 It's very interesting that it's fully vitrified even with only 15% feldspar. I assume it has something to do with the significant amount of flux in the Grolleg, and the relative
  8. The slip is deflocculated with Darvan 7, about 1.7 specific gravity (I don't push it too hard for tests), and the mixture is slightly thixotropic. Your comments about settling are pretty interesting, however, I'm not sure that's the issue here (of course not discounting it either). Reading my original post, I think I misstated the problem a bit. In almost all the tests, the cracks start at the base and work their way up the sides. Only one or two have missing bottoms, but because they look so dramatic I think I fixated on them. A few are also cracked almost perfectly in half. Thanks for a
  9. Hi all, After my rather unsuccessful experiments with a few commercial slipcasting clay bodies, I've embarked on developing my own. I started with the basic 25-porcelain and I've been working from there. I'm curious both on some overall feedback on my recipes, as well as a specific problem I ran into. This is all at ^10. So far, I've tested 4 different feldspars; Minspar, Custer, Nepheline, and Mahavir. I found Custer really doesn't flux as much as I would like. Mahavir seems to be creating odd casting problems. Nepheline and Minspar have been great. Nepheline does have a bit of solu
  10. 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.
  11. 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
  12. 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.
  13. Ah ok, I was pretty unsure, it's quite different than most of the other materials I have. 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. Yup, I did all the tests one after another. I also made 250 g batches so everything should have been pretty consistent between tests. Yeah, I think most of my next round of testing is going to be around improving G0027. Maybe small additions of spod will help with lowering the expansion without creating
  14. I got a tiny bit of froth, but I didn't need to pre-wash it. Surprisingly little froth compared to what most people describe. The texture is a bit weird too. It's very free-flowing (total opposite of wollastonite), and somewhat granular. Quite similar to table salt. I'm wondering if maybe I used too fine of a screen and it got caught? That doesn't make a ton of sense though because I probably would have noticed before I rinsed my screen off. Next time I'm at the community center studio I'll ask the tech there to see his spod. I really appreciate the offer Min, but don't worry abou
  15. First, pictures: https://imgur.com/a/hGDpkE2 I tried to take them at an angle that would show the surface texture, and I embedded some ink in the crazing in some of them. I don't have lithium carb because my local supplier charges $55 for 1 lbs :/. I could try petalite maybe? Or another supplier or just suck up the money? I'll explore this a bit more. 120 F/hr from 2150 F -> 2350 F, then 20 minute hold at 2350 F. ~500 F/hr before that. It provided some useful characterization within the same flux grou
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