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soilandpolish

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  1. Clay & Glass

    This topic really interests me, wish I had more to suggest. If you do try any experiments, I hope you'll share your experiences back here Pazu. Benzine and Matt make some promising suggestions. Like Matt says, if the clay is already fired to maturity (and it and the glass have compatible thermal contraction), you only need to heat the clay the second time up to glass fusing. I wonder if you could join them by hand at that point? Or with something like the Egyptian paste as a slip to help mediate them? Maybe you have some fragments of the antique glass that you could grind to use in that. I hope some others with more experience will add to this thread. I have to admit I have no experience at all. But I've been thinking about trying this, in the context of experiments with mixed/layered materials, graduating and weaving between ceramic to glass like rocks do. Though it doesn't seem really pertinent for your situation Pazu. And you probably do right to join them with an adhesive at low temperature. I hope I'm not annoying anyone with my long post out of ignorance, but I'm enthused, and my last post didn't really address that... Andrew
  2. Clay & Glass

    It looks to me like he's about the patent at the moment, it's mentioned in the second sentence of that page. So he may be willing to tell you how to do it (I think that's highly unlikely though), but if his patent goes through you won't be able to use the info without his permission. And if you figure it out for yourself, you still won't be able to use it, that's how patents work to the best of my knowledge, so ... yeah. Not that I think he does wrong to patent, per se, but let's call a spade a spade. Andrew
  3. How Do You Know When The Clay Is Dry?

    Good luck Melissa, and thanks for liking my post. By the way, I'm also in Canada. Andrew
  4. How Do You Know When The Clay Is Dry?

    Your health coverage must be better than mine!
  5. How Do You Know When The Clay Is Dry?

    You could make a small slab with the clay, weight it before and after a fast drying, and know what percent change to expect for the rest of the wares. You could have the board on a scale and just watch until the expected weight loss is achieved. Or, if all the pots are similar wall thickness, you could just pull one off the board and weight it periodically.
  6. Slip casting globes- form?

    In fact on my last visit to our local pottery supply, the proprietor and I were discussing slip casting (I was wondering about using paper forms dipped in slip -- I've since seen some work done like that seaching online, for example http://www.australianceramics.com/JUNE/origami.html/). She told me that she once dipped a hollow plastic ball in slip, poked a small hole in it, and fired it and it came out well, with just a bit of ash or residue near the hole. Thought I'd pass that on. [edit: oops, I see Marcia already said that this works in the post right before mine, tried to skim them all before posting but missed that, pfft]
  7. My point was just concerning the energy efficiency. Since you wouldn't fill a kiln with furniture if it had only a small load of wares, and nothing else in there absorbs much heat, your energy efficiency is not greatly affected by the density of fill. Possibly, it may even work the other way, that a large load would be less efficient because of the furniture, and because of the insulating effect delaying the radiant heat propagation. But I'm a rank amateur, probably I'm just not getting something... As for production potting, sure you probably want to turn out as many pots as possible, and the energy question is only one part of the picture.
  8. How does heat-work tally up? If you fire and empty kiln to a temperature (or cone), and fire it again to the same endpoint full of wares, how much percentage wise more power is used? I think I'm having calibration issues with my sitter or I'd test instead of ask, but it seems to me, over my three firings so far, that the one full load took 400% longer to fire. I'm really unsure about the sitter though... (Sorry if this is off-topic, but several posters mentioned filling the kiln to save energy.)
  9. Chris, yeah you're right, making more than one tray to start with would be silly. Or designing them to stack before I've even tested one. I'm more theory than practise, so overdesign happens (but you can save a lot of time at a higher level by that). I'm thinking that, since the kiln is so small, custom DIY furniture is more feasible than for usual kilns: the weights involved are smaller (shelves and wares both), and space is especially tight, which justify some nifty trays and supports (like for more general use). Also it's unlikely I'll get a larger kiln for years. I'm just not sure whether I can make the furniture in this ^8 kiln, let alone without buying/lugging a box of fireclay. Hmm... (including a cab ride one way, buying a box of proper fireclay is about $50 minimum investment) ... Would love if could make it with my M340 stoneware mixed with allumina silicate (for which I can exchange the big bag of wash tomorrow, spoke to the supplier). And fire it in this same little kiln. But, would hate for a big load a few firings down the line to smash down, if I could've avoided it by spending the $50! jed: Yeah, that's a sweet idea. Is it a solid or hollow casting? That design looks like it really helps assure equal heating of all the wares over the whole firing. Will the flutes stand freely within the tubes, or do they lean slightly to rest againt the tubes?
  10. That's a great idea, thank you! It would be easier than trying to make furniture which allowed me to fire them upright (which has the warping problem anyhow). In my situation, if I wanted to make say a bottom shelf, and some trays, would I try to wedge like 30% alumina into some cone 6 stoneware clay, and get some Orton cone 8 cones and try firing it in this very kiln? Or would I need to slake my own clay from powders? Maybe I should make cylinders out of this refractory [?] alumina-clay, for the firing of the trays, so that they keep the shape (like firing pots with the lids in place)? I will research about alumina today, it sounds really useful, especially if I can make my own furniture. It probably won't be cylinders next month, who knows... P.S. No home internet, so if my responses are slow sometimes that will be the reason. Also, I noticed the pinned post about attaching pictures, now I know to go to More Reply Options.
  11. Thanks for all the input! Min and John: The cylinders are basically solid, although I'll be trying all kinds of stuff, it's my first kiln. Chris: I'm using a few clays. Right now, it's actually Plainsman M340, a cone 6 stoneware. I would prefer to use their P300, a cone 6 porcelain with lower porosity, but I have none at the moment. I also have some cone 6 casting slip from the same company, but haven't gotten started with mold-making yet. Thanks for the information about "clicking apart" bonded wares. I used my fingers on the stickers last time, but I expect a lot more surface contact area the next time, and especially if I start casting or extruding.... In case anyone has feelings about casting (versus throwing etc.), let me just say, I'm not aspiring to be a production potter, more of a mad scientist type with a love for ceramics. So techniques will be all over the map (if I persevere). John: Actually I'm making use of the diagonal length on the floor, so firing standing would limit my length to about 70% for the biggest pieces. I have fired some standing, but found that they would warp from the heat, I think due to receiving more radiant energy on one side than the other. Have considered building a box of refractory clay to shild them, so could fire a lot standing on end, but I don't have a refractory clay or a kiln hot enough to fire it, so looking for the interim solution. Jim: I didn't know I could mix alimina hydrate with clay to make my own bottom shelf. The kiln is rated for cone 8, but I bought used and have only seen it bend a Orton cone 6 in the sitter. I guess the alimina-clay mixture would not be suitable for making other kiln furniture? Or could you? It would be like playing doll house, making furniture for this little EvenHeat. How thin could I go with that alumia-clay floor shelf I wonder? Marcia and Jim: Great! Not having to use wax is great, as my ventilation consists of a bathroom fan. justanassembler: Yes. I guess I'm looking for decent strength, low absorption, but trying to prevent warping. When I get to using porcelain again, I may try this. It's a sitter-type kiln. Can I use a cone 6 cone but just nudge it over a bit so the guage sits on slightly thinner part of the cone? Min, Jim, Marcia: Thanks very much, this is what I hoped -- that something (alumina hydrate) will not adhere to unglazed wares. I thought maybe the maturing clay would "sweat quartz" or something, making anything stick. Alumina hyrdate sounds like really useful stuff, can protect kiln floor until get shelf, can keep wares from adhering, and can maybe make my own kiln furniture... probably I should try to exchange my 2.5 kg of kaolin:silica wash for alumina! Thanks again to all of you for kindly sharing your knowledge/wisdom/experience! Andrew
  12. Thanks Min and Chris. I think this image will give the idea: ... um, I created an image to illustrate but I can't figure out how to upload it. Picture a bundle of drinking straws, or (perfectly cylindrical) logs. Long small cylinders, piled lying on their side. There is no glaze so I'm no worried about the bottom of the kiln, should I be? As said it's a test kiln, so there's not really furniture available for that. Maybe I could get one made in a kiln that can go to higher temperature, or get a shelf cut. It's internal size is only a cube 6 inches wide. My main interest is how to coat wares in a case like this, that have a large contact area with each other, and are densely packed, so that they won't vitrify to each other. Some coating that can be removed by mild cracking off or mild abrasion at the most (or even say a soak in vinegar or something...). The idea of a wax/alumina hydrate (AlOH3) coating sounds attrative. So this stuff would not adhere strongly to the wares? Maybe I could even spray a thin coating of liquid wax, then dust with alumina hydrate with a ponce? This link shows something like what I had in mind with the shelf paper: http://www.conwedplastics.com/files/7813/5837/1302/snakewrap.jpg (not supposed to hot-link images directly). I don't think this solution will work very well somehow, shelf paper is probably brittle? But even just horizontal layers of it might work. Will 1:1 kaolin:silica wash stick to a typical cone 6 vitrified porcelain body, in the absence of any glazes?
  13. Hi, this is my first post and I'm so glad to have found this forum! I have only a test kiln, so space is limited. I'm firing unglazed cone 6 porcelain pieces, all cylindrical and of similar size (each about 100 grams fired). I want to stack them directly on the kiln floor without the wares sticking to each other. Initial experiments with imperfect forms suggest that sticking will be a problem in the next iteration, when the forms will be more perfectly cylindrical and have greater surface contact areas. I had thought to use kiln wash on the wares themselves to prevent this, hoping to remove the wash with minimal effect to the finish of the pieces. I could just try this ... but I could also return the unopened bag of wash if, as I'm beginning to fear, the wash will adhere strongly to the wares... The pieces could be burnished or roughed going in, it's no great inconvenience either way. But power grinding post-vit would be over the top. Maybe some other substance would suit this purpose better? (This kiln wash is the standard 50:50 kaolin:silica combination.) Ideally, the wash would crack off like a husk, with no bonding interactions with the wares whatsoever. Just read about "shelf paper" for the first time today, and maybe some corrugated wrapping pattern with that stuff would work better? Or would it still bond?... (Today I read in a post on this forum that it's only used for glass, so probably bad idea? And then I read that you could use it but it's a particular health hazard?) Maybe the finish including bonded wash, with a quick sanding, would be acceptable. I could sort of stilt the pieces, placing little interstitial balls of clay -- pretty labour intensive loading, but that would reduce the contact area. But then sagging might be a problem there. Any suggestions will be savoured! Andrew
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