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algebraist

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  1. I think that might work fine for something small, but the platter has to sit in the mold until it's rigid. That entails shrinkage, and if the foot ring is built into the mold, well, the mold is not going to shrink with the clay...
  2. It's a big platter. If I take it out of the slump mold to add a foot (or multiple feet) while it is still easily worked, then it isn't going to be able to support itself, and will deform. If I leave it in the slump mold until it's fully rigid, then it's not so easily worked anymore... It is still possible to add a foot, but arranging for the foot to have the same degree of dryness as the platter is pretty challenging. And if they don't match pretty closely, there is a real risk of the foot detaching during firing.
  3. Thanks -- yeah, I have done that, and it has the obvious benefit you mention. But I wanted to get out of the business of trying to match the foot ring to the platter in terms of degree of dryness -- that can be tricky, and although I have mostly succeeded, when I've failed, it's a total loss...
  4. Wow, that's pretty clever -- a bottomless slump mold, which makes it possible (with some extra support -- such as the upholstery foam you suggest) to add a foot while it's still in the mold. I will certainly be thinking some more about that. Pretty brilliant.... Thanks.
  5. Thanks, there is! I bought my kiln from Neil a few years back (which I highly recommend, for anyone in the market), and part of his excellent advice was to go wide instead of deep -- easier on the back.
  6. Thank you all. Neil is (unsurprisingly) right -- my plan leaves me with a shallow bowl, not a platter, which I arrived at in order to try to solve some problems, but which has its own problems, and in any case is not really what I want. So back to the drawing board. I am pretty attached to the hump mold part of the plan, which has two big problems: 1) I want the platter to be able to dry at least to leather hard on the mold, so it doesn't deform. But it will shrink, and the mold won't. I'm thinking I might be able to finesse this by making the mold support just the flat part of the platter, and letting the rim just hang over, or maybe I can find a length of soft foam or some such. 2) Construction of the mold. Probably my best bet is to throw it on the wheel (I do have a 22 inch medex bat, purchased with this in mind), then use the bisqued form as my mold. Other details: Yes, I am using stoneware, but I should probably pay more attention to the precise variety -- as I said, I've been using whatever has dried out too much to easily throw on the wheel. And I will go a little thicker. A waster slab for the glaze firing is so obvious I can't believe I didn't think of it (thank you); of course I don't have a 22 inch waster slab lying around... but will make one.
  7. 22 inches is the widest slab I cab make with my slab roller, and I am beginning to become obsessed with making a 22 inch platter. It has to be footed -- there is no way it will ever come out flat enough to sit nicely otherwise (plus that permits glazing the bottom), and it probably needs multiple feet for support, or something creative (like maybe straight line supports radiating out from the center...). My first attempt, in which I took the flat slab and just stuffed old rags under the edge to make a lip, and then affixed many small circles underneath for support, was basically a failure -- it sagged and stuck to the kiln shelves (I cleaned it up best I could; it hangs on the wall now). My second attempt is not looking any better -- for this one I laid the 22 inch slab over a 20 inch slab to form a lip and affixed two foot rings, but I inverted it too soon and it went into the bisque pretty close to flat. I expect it to sag during glaze firing, which will be most unpleasant... My latest idea is to build a plaster hump mold using the inside of a large convex mirror. There is a 26 inch (diameter) model available on Amazon, but it has very little "rise," and I'm concerned I'll have the same problem. Here is a picture of it from the side: (I am assuming I will be able to detach the mirror from its backing to fill it with plaster...) On the other hand I can get a 22 inch diameter hemispherical mirror (my slab would only drape partway down it -- there would be about 6 inches of the base of the mirror left all around), but I think that would be too bowl-like and not enough like a platter. I can also get a larger hemispherical mirror, which might be the ticket, but the price goes way up, so I'm less inclined to experiment. Other information: I'm pretty much set on a hump mold, as I've made smaller platters (successfully) in a handmade bisqued slump mold, and it's tricky to get the foot ring on properly -- the platter dries out some, and matching the state of dryness of the foot ring with that of the platter is difficult. With a hump mold, you can attach the foot ring(s) right away. Also, I know I could save myself some trouble and just use the mirror itself as a hump mold, but I think I'll have better results with plaster, as the clay will dry from both sides, and there shouldn't be a sticking issue. (And as it dries and shrinks, the shape being spherical, it should just slide around on the mold -- so I can let it firm up pretty well before removing it.) Finally, and maybe this is the kicker, I've been rolling my slabs about 1/4 inch thick (it sounds thin, but it looks thick...). Maybe I just have to beef that up some. And I tend to be using clay that has dried out (in its bags) too much to lend itself to throwing -- it seems those bags are not perfect, and there is a time limit... I buy in quantity, and then never throw it all quickly enough. Bisque firing to cone 04; glaze firing to cone 6. Thanks in advance for any thoughts.
  8. Wow, so much information... Clearly I am out of my depth here, but seeing as I will be doing it anyway, so much appreciated! First, I should have been clearer: Yes, inside, most definitely, and yes, it has to be movable. Essentially, a ceramic painting. (I guess "mural" has some outdoor connotation; it never occurred to me, but is an intriguing thought... Sometime down the road perhaps.) Second, no, I had no idea there were different grades of plywood... And then so many other options. I looked into cement board and hardie board, and apparently they are very heavy, which is a detriment -- I am really trying to keep the weight as low as possible. Which makes Bill's suggestion most appealing. It's been about two decades since I last used my router (and then only a few times ), but I wouldn't mind getting reacquainted. And I will need something framing the outside of the work anyway, so it may as well do double duty and help keep it flat. If that lets me use thinner plywood, that's a big win. Finally, I will look into hydrotec -- better quality plywood should mean that a thinner sheet should do. I have not yet started thinking about adhesives; I suspect I will be back with more questions when I do. Thanks again, all, so much.
  9. I am just starting work on what will be a mural made from twelve 8-inch tiles, arranged 3x4, so roughly 24 inches x 32 inches (plus a little extra for the minimal amount of grout between the tiles). I have been using Frank Giorgini's "Handmade Tiles" as a reference; he recommends mounting the tiles on 3/4 inch plywood which has been braced with strips of 3/4 inch plywood along the edges, and then hanging it via yet another strip of 3/4 inch plywood which has been cleverly cut lengthwise on a 45 degree bevel, with one half attached to the back of the mural, and the other half attached to the wall (screwed into studs) -- that way the bevel on the back of the mural just slides down into the bevel attached to the wall, and the whole thing is secured. All well and good, but heavy! If that's how it has to be okay, but I am wondering if I can get away with 1/2 inch plywood, and bracing it with (nominal) 1x3 or 1x4 inch pine boards (and making the support strip from the same). Or if there is perhaps some other comparatively light option. (Presumably the concern is that the board may warp, with potentially disastrous effects to the mural, thus the thicker the plywood the better. But my back hurts just thinking about 3/4 inch plywood...) Thanks.
  10. Thanks, Neil, for the very helpful information -- greatly appreciated.
  11. Sorry for joining the conversation late, but I am just starting up some tile production, and need to ask: Do you not worry about warping during bisque firing? If warping is unlikely, then I love the domino and vertical ideas; otherwise I might have to go all out with individual tiles on tile setters like I will be doing for glaze firings. Thanks in advance for your thoughts.
  12. Thank you all for the suggestions -- lots to try (as always!).
  13. Hi All -- I am looking for a (cone 6, oxidation) crackle / crawl glaze that gives nice, bold geometric patterns with a lot of contrast -- white on black or maybe vice versa (so I am really looking for two glazes or maybe a glaze and a slip). Here are some examples of what I'm talking about: (I suspect these two are very different in terms of what's going on, with the first being more of a "crawl," and the second more of a "crackle"... But the usual "crawl" glaze tends to be more rounded and circular, and I like the more geometric, rectangular pattern of this example.) Any suggestions on where to start would be greatly appreciated.
  14. Thanks -- so Seattle Pottery, Sheffield Pottery, and Krueger Pottery appear to be on the list. (Just looking for places that ship -- you mention Chicago Pottery Supply, but only for local pickup.)
  15. Hi All -- Somewhere here I came across a post describing which businesses were still shipping clay, but I can't seem to find it. Anyway, I found myself out of nephylene syenite, which I need for my new favorite glaze, and thought I would share with the group that Bailey Pottery is still shipping (although it is hard to tell from their website -- if you wait long enough, a message scrolls by). Shipping isn't cheap, but what are you going to do... I couldn't decide which was the right forum to post this is in; feel free to move it if you see fit, but I thought perhaps others would like to chime in and we could grow a list. Hopefully you're good and stocked up, but eventually things run out...
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