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BlackDogPottery

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Everything posted by BlackDogPottery

  1. Producing Models

    I was recently contacted by an industrial manufacturer to throw some large-ish planters to create rubber molds from then to cast other materials from these molds. The question is would it more practical to make these from an earthenware than my usual stoneware since they will just be masters? The pros being- earthenware being less risk in firing, less shrinkage (as I mentioned they are big), and overall user friendly clay. My stoneware is funny as in clay memory like an elephant and these are expected to be almost perfect. The con to me is something just doesn't feel right about using the weaker clay as if it wont be "authentic" enough. I'm afraid they might crack during the casting process of pouring rubber but they're pretty thick at half inch wall thickness so is that just being paranoid? Any guidance would be helpful as there's not much out there about the humble home potter working along industry.
  2. Producing Models

    So do you think I could get by with sending a bisque form?
  3. single firing, cone 6 stoneware

    I have one of those too that I throw all my unused white glazes and sometimes a little bit of slip. Interesting thing to see how some of the whites change to the creamier side or grey side with usually a few soft specks of cobalt and copper (from the clays I guess)
  4. Rutile Glaze

    Update. I added rutile to my base glaze and it didn't come out anything like I would imagine. 4.5% Rutile . A soft grey that unusually turned black manganese specks to an orange rust. Bizarre to me as I was expecting a yellow. However its pretty nice to me and cant wait to use it. https://imgur.com/leYKL0Z 4.5% Rutile : 4.5% Red Iron. Even more surprising was this odd shade of black https://imgur.com/OEQTuvv
  5. Rutile Glaze

    Hi. I was doing some research for trying to make this kind of muddy yellow color and found a few recipes that use rutile. I have some powdered rutile light that I was thinking of using. Any recommendations on how to much to add to a clear for starters? I've never used it before so does it make glazes runnier or anything like that? I was thinking 5% first. Thanks
  6. Plaster clay

    Has anyone heard of this before? http://ceramicsfieldguide.org/pdf/uncommon-clays-glazes-processes/PlasterClay.pdf Seems like it fires extremely low but I cant think of much that you would use this for. My guess are those plaster wall decorations/ plaster picture frames. I've heard of people adding plaster in glazes but a plaster based clay?
  7. single firing, cone 6 stoneware

    I've been single firing for a quire a few years now and in my experience just about any glaze will work but the main issue you run into is having the glaze stay put. Some glazes with Gerstley Borate will gel on their own and apply evenly and stick to the pot. Others require Gum Arabic to stay on or they flake off and this always leads to crawling. What works for me and glazes that wont apply nicely is 4 grams of Gum and 80 grams of water per 100 grams of dry ingredient. This will require about 3-4 coats but you can cut the water in half and apply in 2 coats, cut it again and apply 1 coat. Depends on how thick you can get your glaze before its unbrushable. Some recommend leather hard glazing but I find bone dry because if you glaze on leather hard the clay continues to shrink but the glaze doesn't (it flakes and falls off). You can also pour the insides at bone dry just dry it out slowly. Depending on how far you want to go you can also mix certain clays together as some react better to water absorbtion. My stoneware always cracks but adding in 1/6 of Terra Cotta helped it go through the shock of water and after firing the bonus of a stronger feeling clay body. It just takes a little patience and a little courage.
  8. Would just like to mention that I believe the toxicity of iron oxide in glazes is a fraction compared to it's use in multiple cosmetics. Lipstick, eyeshadows, blushes, and whatever else are applied directly to the skin, digested, or inhaled. You get the point, very rarely do you ever hear reports on that as it would most likely be linked to lung issues than an overdose. Also wonder about the effects of gold and other luster. There's plenty of dishes with rims lined in gold or silver. I'm sure if there's any way of it coming off it must be extremely minute, but it's something to think about.
  9. Zinc in glazes

    I was going through more glaze research and came across an interesting note on zinc being easily soluble in glazes when strong acids are present. I've seen a few glazes with zinc and one I use myself. From what understand zinc is a flux. Is it uncommon or would it be practical to replace zinc with some kind of frit or borate if its so easily to dissolve in a glaze?
  10. Zinc in glazes

    "The use of zinc in standard glazes is limited by its price, its hostility to the development of certain colors and its tendency to make glazes more leachable in acids (although zinc itself is not considered a hazardous substance)." From Digitalfire https://digitalfire.com/4sight/material/zinc_oxide_1718.html . I also have an old 70 ceramics book that more or less notes the same thing. Just curious.
  11. Zinc in glazes

    Sorry if my question missed the mark but I was meaning is the zinc leachable after firing. As in a zinc glaze inside a coffee cup.
  12. Zinc in glazes

    It's definitely a good opacifier. I ran a test substituting the zinc with borate plus another 10% borate. The difference was night and day. The zinc version was very opaque with a nice smooth surface, off white. The gerstley borate trial was clear as it could be but crazed all over and cracked the piece in half from thermal expansion I believe, the surface however was smooth but felt cheap like imported earthenware.
  13. Zinc in glazes

    Yes, that's it. It mentions zinc can leach but it's not a hazard unlike copper or cobalt. But it made me wonder why use something that could leach when there's other materials like borate that could do the same thing? Is there pro's and con's with using zinc in a glaze besides being an active flux?
  14. Pitting and pinholing

    Is this on the inside as well? Could be from trimming too. I've noticed pinholes on pots that only appeared where it was trimmed (bottom 2/3 of a pot). It seems throwing seals the clay off in the interior and elsewhere. I would try sponging the whole pot down next time and see if it makes a difference.
  15. What's your Mug?

    As the title says. What's your mug? Almost everyone has a favorite mug, what's yours? What do you grab in the morning? A stout standard cafe mug or a bulbous mug that can quench an army? I'd like to hear!
  16. Handy Techniques

    Big ol box of 6" x 6" bathroom tiles. Use them for bats. Sure are a lot cheaper than the bats you can buy at the supply store. They stick pretty well to the wheel head and cant warp!
  17. Handle Help

    I've been having some issues with handles on mugs. I'm working in ^6 pale stoneware and have tried multiple tricks like adding different clays, paper slip, and vinegar to help it along and such. It's specifically handles. I haven't even had issues with joining almost bone dry vase parts together with nothing but water. Pull the handle, let it firm up. Slip and score as usual on an almost leather hard pot and go from there. However I always develop these hair line cracks around the seam on the top of the handle, sometimes the bottom. At one point I tried pulling the handle off the mug too. Nice fluidity but nevertheless thin cracks appeared right at the seam. The handle is joined sufficiently as I can pick it up at bone dry and have fired some that were cracks for home use. Completely usable but these hairlines become prominent after firing and who wants to buy a cracked mug? I have a feeling the seams are cracked from lack of compression. Does anyone compress their seams with a tool or something? Or is it something I missed. Any input would be greatly appreciated
  18. Red Clay

    Another update. 50 : 80 mixture. A completely matte stone like finish, black without any trace of brown and nice to the touch. No runs.
  19. Red Clay

    Through researching many recipes, old and new. Occasionally I come across recipes that have "Red Clay" usually at half the recipe and the like. However I'm not sure what red clay is? I think its considered terra cotta but is something like Redart specifically? Thanks.
  20. Handle Help

    Update. Put handles on a lot sooner, added a coil of clay around the seams, blended with a tool, and dried way slower under plastic. I believe that was the problem, speed drying on top of a hot kiln what was I thinking lol? So far so good. Lets see if they can survive being raw glazed!
  21. Tools for throwing dry

    I know this was directed for a specific person but I also dry throw. I use lots of metal tools/ribs. Flexible metal ribs for the insides and flattening the floors. Hard flat metal strips or razor blades to help pull walls. I think one of the better points of dry throwing is getting more out of your clay and better development of shape. However things tend to be on the thinner side for me which can be good or bad depending on your style. Clay can torque or tear depending on how short the clay is but using metal tools puts less resistance and can help.
  22. Handle Help

    Thanks everyone. Will try some of these. Hate to admit it but its kinda hard to bring yourself to waste a bunch of mugs to handle!
  23. Ian Currie Test Tiles Forums?

    When you run your Currie test do you mix up a big batch of base glaze and take what you need as you go or do you mix up several 100g batches?
  24. Red Clay

    Thank you. This is a cold cone 6. For the running so far it depends. At 1 coat it doesn't run but its not as smooth. 2 heavy-ish coats or 3 light coats the sweet spot. It does move some but it doesn't look like drip, more of a slight sag at the base where it collects. So I would set a kiln cookie under it for your first trial. Another test I did with 1:1 ratios sagged slightly more which is a surprise as you would think more clay would equal more stability. %60 Manganese Dioxide %40 Red Clay %75 Water
  25. Red Clay

    Yes. The vase you see in the first set of pics is a very cream body. Just your average stoneware clay.
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