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algebraist

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Everything posted by algebraist

  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...
  16. Hi All, I threw a few cups yesterday, intending to trim them and turn them into mugs today. But I left them uncovered too long, and now the rims are very dry -- maybe not bone dry, but they've lightened in color, while the bases are approximately leather hard. (I threw on plaster bats, which absorb quite a bit of water, left the cups on them, and forgot to consider that it was a very dry day around here yesterday... Timing is everything...) Anyway, I could just trim them and call them cups, but I'd much prefer to put handles on them, and I like the handles to attach pretty close to the rims, and so the current situation is far from ideal. My question: Is there any way to safely rehydrate the rims? I'm thinking of things like misting lightly with water, wrapping in moist paper towels, or even a quick dunk in water, then wait a few hours and go from there. Or is this one of the worst ideas I've ever had (and I've had some clunkers...) -- I'm imagining what happens to a truly bone dry piece of greenware when soaked in water -- it disintegrates -- so maybe any attempt to rehydrate would severely compromise the integrity of the pot. Thanks in advance for any opinions and/or suggestions.
  17. Since we're talking trigger thumb again, I (as the original poster) may as well report in. The hand specialist I saw suggested that cortisone would just be a temporary fix -- 6 months at best -- so I didn't bother with that. He is a surgeon, so naturally advocated the surgery that you had so successfully. But I am surgery-averse, and went with the third option: I wore the custom made hand brace every night, not just for the 8 weeks he had suggested, but for about a year and a half... Also, I very quickly developed trigger thumb in my other hand as well, so I was wearing braces on both hands every night. (Try to do anything without either thumb...) Anyway, the punchlne is that that seems to have cured me. No surgery needed, but a lot of patience, and very limited pottery during that time.
  18. An update, in case anyone else finds themselves with similar trouble: I finally had my appointment with the hand specialist; it's "trigger thumb," which is "trigger finger" of the thumb. As you bend the thumb, it snaps open or closed, and this mostly happens after resting it for a long time -- like when you wake up. He wants me to spend another 8 weeks using a brace pretty aggressively -- always at night and sometimes during the day, and if that doesn't do it I get the cortisone shot, maybe another if necessary, and eventually there is surgery. But probably it won't go that far. I've been doing almost no throwing, and will have to keep it that way for a while. And my other thumb just started having the same problem -- no pain yet, but occasional snapping open and closed. Probably it got stressed by picking up all the slack of going thumbless with my right hand -- try turning a key or closing a ziploc bag -- nightmare.
  19. Thanks. It was my primary care physician who made the diagnosis; I'll be seeing him again soon and will ask about a specialist. And I'm trying to avoid the cortisone shot -- probably it's the right thing, but I've had a couple. Depending on where they do it, it can be no big deal or horribly painful. The thumb sounds like the second of those options... Thanks for the advice.
  20. I truly appreciate the offer, but I don't think it's necessary. Yesterday I searched through the many posts on centering here, and then looked up Tim See's YouTube videos on centering. Very graceful, with very little stress on the hands, and very little use of thumbs. My centering was okay in the sense that I could do it, but it seems I was powering through with bad technique. Once I'm back in the game, I'm going to be trying to mimic his technique. Thanks again.
  21. Thanks -- thumbless throwing in the future. For what it's worth, I read more about DeQuervain's Tenosynivitis (you'd think it wouldn't have taken me a month to do so), and maybe the doc got it right. In any case, I'd still like to hear from anyone else who's had similar troubles.
  22. I've been away from the wheel for about a month due to a thumb injury -- I woke up one night with severe pain in my right thumb. I hadn't been throwing that day, so I've been clinging to the hope that it's unrelated to pottery, but today, feeling mostly better, I sat back down at the wheel and immediately found the problem (and set my healing back some...). Basically, throwing is pretty stressful on the thumb. In particular, when centering by the "cone up, push down" process, during the push down phase my right thumb is braced against my left hand for stability, and there is a lot of pressure exerted on the thumb. Based on the way it hurt, I think I can safely say that it's this pressure that's giving me trouble. (The thumb also does lots of other work -- during the cone up I've been using the edge of my thumb to keep a hole from developing at the top of the mound, for example, and I suspect it gets plenty of work as well during pulling up the walls of the ware -- I couldn't fully investigate today because, in a rare show of prudence, I stopped.) I went to the doctor a couple of days after it first started hurting, and was diagnosed with "DeQuervain's Tenosynovitis," which is an inflamation of the sheath that the tendon that connects the thumb to the forearem passes through. For that I was told to wear a brace with a thumb "spica" (stabilizes the thumb), and given some exercises to do when it started healing. I now think the diagnosis is wrong, and will have to go back to my doctor to discuss it, but I figured I should also ask here in case this is the well known "Potter's Thumb" or some such. (Just Googled "potter's thumb" -- don't. Yuck. It's not that.) Experimentation has shown that wearing the brace at night is a good thing, but wearing it during the day as well is definitely bad. So far the exercises seem to neither hurt nor help. Finally, in case it helps identify the trouble for anyone who's had something similar, the pain that started suddenly one night happened when I extended my thumb out straight -- I got an immediate shooting pain accompanied by a spasm in my thumb. So I guess I am back on the injured list for a while. Luckily I have enough sitting around for a bisque firing, so I can do that and then keep myself busy glazing for a little while. If necessary I can also focus on slabs while the thumb heals. In the end, though, I definitely want to get back to the wheel, and might have to look into alternative centering techniques. Thanks in advance for any suggestions.
  23. Thanks for the advice, and it's nice to hear they're a good company. I'm not sure what they can really do for me -- I bought them an hour's drive from here, and I'm not inclined to make the trip again for a while (or my first step would be to tell the store I wanted to return them). And the postage would probably be prohibitive to do it by mail. But maybe I'll contact the company anyway and see what they say.
  24. HydrO-bats -- just double checked. Nice idea drilling new holes -- I may as well give it a try. They rubber coat the holes, though, which I don't know how to do, and maybe without the coating the holes would wear down over time? Anyway, better than relegating them to drying bats.
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