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  1. This is an old thread, but I wanted to correct some potential problems that could arise from advice here: Slip problems arise from one or both issues: weight (specific gravity) and thickness (viscosity). Any slip recipe has an "ideal" weight and thickness. Both of these properties can fluctuate as slip ages. If your slip is too heavy, you can lighten it by adding water. BUT: Do not add water to your slip without checking specific gravity by weighing your slip -- not a hygrometer. Research has proven this, and it's what you'd be taught if you went to school to be a ceramic engineer. Your slip recipe will have an "ideal" specific gravity, likely between 1.75 -1.78 If your slip is too thick, you can fix it by adding deflocculant. But: Do not add deflocculant without checking viscosity with a viscometer (unless you're adept at estimating viscosity by look/feel). Bubbles in slip and castings result from air being suspended in the fluid. This often happens with a new batch of slip, when the dry materials have not fully soaked, and if the slip remains too viscous (too thick) to allow the bubbles to easily gather and rise. Proper mixing and proper deflocculation typically remedies the bubble/pinhole issue. Check the specific gravity and viscosity of your slip before you begin pouring for the day, and you'll be able to fix these issues before they arise. Then you can rock the casbah.
  2. Magnet

    Reducing thermal conductivity

    Thanks again for all the thoughts here. I reckon these are yunomi-of-sorts, though their use is more on-the-go... so they're just cups. I also make guinomi and chawan, for their proper applications... maybe I should stick with them... But I'm trying out a few practical solutions with glaze and other methods, so we'll see how it goes. Yes, too bad it's not easier to crank out a hundred double-thin-walled cups with cellulose-fiber cores...
  3. Magnet

    Reducing thermal conductivity

    Thanks for the considered replies. I should've specified my aim: I want to keep the drinker's hands from getting burned. My porc slip body is quite conductive, and a fill-up at a coffee shop would make the cup too hot. There are other solutions (such as a sleeve), but these will be for production, and I'd like to solve the problem by dealing with the native form itself. Also, these will not have handles -- or the hot wall wouldn't be an issue. I am intrigued by the suggestion of putting air into the mix -- I've used perlite before to get a pitted/lava texture on sculptural pieces, but that's not the look I'm going for with these. I don't think a slip-dip would smooth out even a fine sawdust texture enough for my application here. Thanks for the suggestion. Any other ideas?
  4. Howdy all. Can anyone share knowledge about reducing thermal conductivity of clay wares, other than making thicker walls? The story is: I'm slip-casting coffee cups in porcelain, and want to keep them light. They are lined with glaze to just over the lip, and the exterior is bare clay; I prefer this texture and look, but I know that a glaze will block some of the heat, so I plan on trying that. Though, I wanted to ask you folks if you had insight into the problem. Thank you for any help.
  5. Sweet! Thanks a heap for the considered answers and that excellent chart. Now, to the plaster!
  6. My subject says it all. I've done it with plastic and of course ceramic, but I'd like to make a one-part mold of a glass that I have. Simple cup, no undercut. If it were plastic I'm sure it would work perfectly. I've made many molds before, just never out of glass -- so I'm hoping that someone has experience with this so I won't waste time on an unfruitful endeavor. I'd appreciate any experienced advice. Thanks!
  7. Thanks for the replies. I'm trying to keep the process as simple as possible. Applying resist takes time and material. Also scraping changes the shape and texture that I've established. Maybe I didn't let the slip or underglaze dry enough, but I'm pretty sure I did... 30+ minutes. I've tried both slip and underglaze. It would get wet when wiping away anyway... This is what I'm talking about: https://www.instagram.com/p/BBlorlmBMjs/
  8. Hi all, I've been trying to inlay a black slip into fine lines I've carved into a leather hard slab of white stoneware. The problem is that when I go to wipe off the excess slip, it smears into the clay and can't be cleaned off -- a problem that seems amplified by the groggy clay I like to use. I've also tried inlaying the slip after bisque, but that also doesn't work well. I've read about/seen clips of others doing this with a porcelain clay body, and I'm wondering if that's what I need to use? I assume the smoother nature of the clay lets you wipe away the excess slip more cleanly... Does anyone have experience with this? I'm familiar with the mishima technique, and using resist then carving through and inlaying -- but I don't want to use either, if possible. Thanks for any advice.
  9. Magnet

    Flat Matte Blue ^6 Recipe?

    Thanks, Min, for the feedback. The glaze will be not be used for food-functional pieces. However, I just read digitalfire's page on the dolomite matte base glaze, and I'm going in that direction. I have a lot to learn about ^6 glazes, and Insight/digitalfire looks like a great direction for me.
  10. Magnet

    Flat Matte Blue ^6 Recipe?

    Here are two that I came across in an old binder in a co-op that I work at. I'll run some tests on these soon, but would like to hear if anyone has experience or reservations about these recipes. Thanks for any help. ^6 Oxidation Matte Blue Nepheline Syenite 34.95 Kaolin 17.43 Silica 16.42 Wollastonite 12.03 Strontium Carbonate 10.68 Zinc Oxide 5.84 Lithium Carbonate 2.65 Total Base: 100.00 ADD Copper Carbonate 1 Cobalt Carbonate 1.5 Total: 102.50 ^6 Matte Dark Blue Custer Feldspar 45.6 Edgar Plastic Kaolin 18.4 Whiting 16.6 Zinc Oxide 6.4 Red Iron Oxide 4.2 Silica 4.6 Cobalt Oxide 4.2 Total: 100
  11. Does anyone have a recipe for a stable, matte blue cone 6 glaze? Something like this...
  12. Ok -- thanks folks. It's starting to seem more and more foolhardy to buy this without seeing a test run. I'll look into taking a 240v generator -- as that's the only power option. Otherwise, the peace of mind provided by buying a new kiln with a warranty would be worthwhile.
  13. Many thanks for the feedback and suggestions, folks. I've arranged to inspect/pick up the kiln this coming Saturday, as it's a bit of a drive... It's a bit of a risk because the kiln in being sold "as is". The owner says that I'll be able to see that it was used little, and there's no reason that the controller wouldn't work. I've asked for a quick test, but power is apparently not available -- unfortunately. Of course, that makes me a bit nervous, but I suppose it's also true that brand new kilns can fail as well. Of course, I'll inspect it closely for any signs of overuse/damage. If there's anything else I should look for, I'd love to hear. Thanks again.
  14. Thanks for the detailed considerations. As noted above, the kiln has a claimed 10-15 firing hours, from a small store-studio that's going out of business. Asking 1600 with no furniture or vent. I was told that it was bisque fired and glazed fired only a few times to cone 6 tops. It ended up being too big for the space and was moved to storage... Though, I was just told that it's stored on a pallet in the owner's warehouse, and doesn't have access to power. She said that I'd see that it's in near-new condition, but won't be able to plug it in. I understand about kiln brick and electricity separately so I think that I can judge the condition of the kiln itself OK, but there's no way for me to tell with the processor is broken, or something else that I'm not thinking of... Should I agree to buy only if I can plug it in ?
  15. This is a 1 zone -- 1 thermocouple Single phase Yes, 3" brick on this one. Gonna check it out in a couple days... Any other opinions or concerns for this kiln? Big thanks again

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