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About Rockhopper

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  1. I mentioned this before, but did you try drilling a hole in the bottom of the dish ? If air can't get in, the plaster's not coming out, no matter how hard you pull (at-least not in one piece). It's the same effect as a suction-cup firmly pressed onto a mirror or smooth piece of metal: If you pull on the center of it, it's going to stay - but if you slip a fingernail under the edge, so air can get in, it will pop right off. What are your 'forms' made of? If they're plastic or metal, you should be able to drill a small (1/8") hole that will let air in, but not prevent being able to use it again as a mould by covering the hole with a piece of tape on the outside. Something else to look at: Are you certain the sides are 'straight', and not tapered inward ever-so-slightly ? If it's even a tiny bit narrower at the top than at the bottom, you're fighting a losing battle - even if you do get air in from the bottom.
  2. Yes... for the same reason you can't throw a piece to the desired finished dimensions. If you make the mold from the finished piece, then the pieces you make from the mold will be smaller, by whatever the shrinkage of your clay is.
  3. Could be they're "vacuum locked". In order to get the plaster out, air has to get in. With sloped sides, as soon as the plaster moves even a tiny bit, it separates from the sides, and air can easily get past it into the dish and break the vacuum. The straighter the sides, the farther it has to move to reach a place where the plaster is narrower than the dish, so that air can get in. The mineral oil may actually be working against you in this situation, as it creates a flexible seal between plaster & dish. If you're not up against a deadline, you may find that just waiting a day or two will give the plaster time to shrink a bit as it dries, and create the needed gap. If you don't care about the dish, drilling a small hole or two in the bottom might do the trick.
  4. Rockhopper

    What’s causing this crawling?

    Looks like you're copying and pasting "thumbnails", rather than the actual images. I see a "Photofy" watermark at the bottom corner. I'm not familiar with that app/site, so can't offer much help in getting the full-size pictures... maybe there's a "share" button that will generate a link - or, maybe you can upload directly from your computer (or device you took the pic's with)
  5. Rockhopper

    Pottery wheel belts

    I've not had to replace a belt on my wheel, so don't have experience specific to that, but there should be no reason you have-to buy the belt from the wheel manufacturer - if you can find one elsewhere that's an exact match. If you go to an auto-parts store, take your old belt with you, and ask them if they can match it. There are several aspects to compare, and you'll need to match all of them: In addition to length, width, and number of grooves - the spacing and depth of the grooves, and the overall thickness of the belt are also important. If the belt is too thick, it may not bend sharply enough to go around the relatively small drive pulley on the motor. Other possible sources might be an appliance parts store, or industrial supply. It is unlikely that Brent, or any wheel manufacturer, uses belts made exclusively for them. Often, a belt will have the manufacturer's name and part-number printed on it. If you can read that information from the old belt, a google search may provide you with multiple sources to buy on-line.
  6. Rockhopper


    APT-II sells several products (http://www.apt2products.com/) Not sure they're all truly unique from each other, as at-least two of them have nearly identical descriptions. It's described as an 'acrylic emulsion'... and, in this situation, would be considered a bonding agent that is supposed to help the wet 'over-glaze' stick better to the already fired surface. I've never used it with glaze, but I'd say if the 'Envisions' is sticking without it, there's no point in scraping it off just to re-apply with the additive. If it's not sticking, add some APT and see if it helps - but don't add it to the entire container - put a small amount of your Envisions in a cup and add a drop or two of the APT. That way you're not altering the entire container of Envisions if it winds up not working. Either way, you'll need to be extra careful handling the piece after it dries, especially when loading the kiln. Even with the APT, the added glaze will definitely be more susceptible to being scratched/chipped off if it gets bumped against a shelf or another pot. Also: Preeta mentioned that the Envisions will look different over another glaze than it does directly on the clay (looks like all of the samples on their website are on a white clay body). You should also be aware that the second firing may also cause color changes in the already-fired Courtyard glaze.
  7. Sunshine & fresh air are probably your best option. If you're going to try vinegar - start slow, and test on one or two first before you do the whole batch.. It might be acidic enough to damage the plaster. (Plaster walls usually have paint on the by the time you want/need to clean them - so you're putting vinegar on the paint, not on the plaster itself) You might also want to try a product called Zorbex. I've never used it on plaster - but it worked well on wood furniture that came from the home of a smoker. No matter what you use, don't be surprised if the odor returns the first time you actually use the molds, as the water from your slip works its way through the plaster and re-moistens the smoke residue.
  8. Rockhopper

    Brent Wheel not turning on

    If/when you replace the fuse, make sure the new one is a slow-blow, as Mark said. A motor draws extra current when it first starts up, and a regular (fast-blow) fuse won't be able to handle that initial load. You can probably get them at a hardware store or home-center, but make sure you check the package yourself, because there's a good chance that the person working in the store won't know the difference - especially if you go to one of the 'big box' stores.
  9. Finally got them finished, so thought I'd share a pic. Made the smallest one first, with rim folded over to create the gallery - then went a different direction and collared-in on the other two. The biggest is about 7 pounds, plus the lid, made in two sections (a large dish with a bottomless cylinder added). I think I got the diameters about right, but neither of the larger ones is as tall as I was aiming for. If I make another set, I'll probably add another 2 inches to the height - at-least on the biggest one. Overall I think they turned out pretty good for a first go at something that big, and my wife says they look great in the kitchen, so I guess I can call the project a success
  10. Thanks Mark. All bisque - no re-fires. Haven't been at it long enough to have broken shelves. Need to pick up some 1/2" & 1" posts next time I'm at my local supplier.
  11. I'm sure there are other threads about this, but have not figured out the right combination of words to find them via the forum's search engine.... In a glaze firing (electric / cone 6 / stoneware): How much space should there be between the top of a pot, and the under side of the next shelf above it. Obviously, I don't want the pots to touch the shelf, lest they wind up fused to it - but what is a safe minimum. If all of my posts are in two-inch increments (obviously, I need to get some shorter posts - but until I do... ) am I safe leaving minimal (1/8") space - or should I add another two inches ?
  12. Rockhopper

    Newbie to Stoneware

    What does your clay supplier say ? The stoneware clay I use, from Standard, says "suggested bisque temperature: ^04".
  13. Rockhopper

    how i can learn C#?

    Interesting how the reader's background influences interpretation of abbreviations... When I saw the title of the post, my first thought was "somebody must have posted to the wrong forum"... I read the 'C#' as "C-Sharp", a computer programming language. (https://en.wikipedia.org/wiki/C_Sharp_(programming_language) I'm guessing Fred's interpretation is probably much closer to what the OP is looking for.
  14. Rockhopper

    Red glaze question

    Others, with more experience & knowledge than I, may have a different response - but I would say if your work is fired to maturity (both glaze and clay), and there is no cross-contamination from other pieces in the kiln, then a food-safe glaze on a food-safe clay is going to be food-safe. However - even the "dinnerware safe" glazes you mention have disclaimers that say it's the responsibility of the user to test their finished product to be certain it's safe... (Example from one of Amaco's Potters Choice glazes: "Tableware producers must test all finished ware to establish dinnerware status, due to possible variations in firing temperature and contamination.")
  15. Rockhopper

    Blistering / What Causes it?

    I see holes spread across most of the white glaze. Looks like it's doing the same thing all over - but it's thicker at the bottom, so the bubbles don't pop - and turn into blisters instead of tiny craters.

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