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Magnolia Mud Researdh

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  1. High Bridge said: "A test I have run is to put a blob of glaze on some already glaze-fired bare clay and see if the bubbles are still there. In theory the already fired clay shouldn't be releasing any gas." good idea. Assuming that you would get bubbles if you ran the HB's test, the most likely source of bubbles would be the clay component of the glaze recipe. Try calcining the clay and use something like CMC to keep the ingredients in suspension. Or just try another source of clay such as a clean kaolin. LT
  2. I routinely fire glazed cups, bowls, and whatever on seashells filled with wadding. The shells leaves a mark where it touches the glaze. Soak the marked area in water to crumble the white stuff (aka calcium oxide) that remains after the shells are calcined by the firing. The mark can be polished with a whetstone. the rims and walls of bowls and cups will distort if the weight of the object is greater than the strength of the material but that is a pot design problem, not a firing problem. The technique works fine in a combustion kiln, but there is no obvious reason not to use the technique in an electric kiln. Testing is advised, and YMMV. LT
  3. I use a slip made from my favorite white earthenware clay body, and since it (white earthenware clay body) comes from the same clay supplier as the white version of the red clay body, the shrinkage issue is minor. On porcelain and stoneware, I use often use slip made from a different clay body for decorative purposes, especially for sgraffito. I even use earthenware slip on cone 10 stoneware as a "glaze - like" treatment. It is a good idea to try it as a test before using it on your MFA final exam piece. LT
  4. Get in touch with Arnold Howard at Paragon. He will give you the information you need. http://www.paragonweb.com/ LT
  5. Most of the flat slab objects I have seen cracking in the last 10 years have been due to uneven cooling due to the temperature differences between the top and edges and the parts in contact with the kiln shelf. When I switched to placing the objects on balls of wadding (half and half by volume alumina hydrate and epk) such that "slab" is at least a fingers thickness distance from the kiln shelf, cracking failures dropped significantly. The logic is that the edges and upper surfaces are the first to cool and the shelf and the bottom surface is the last to cool. Since the bottom surface of a flat object is in contact with the shelf over a large area the rate of cooling of the bottom is determined by the mass of the shelf, not the mass of the object. The wadding balls disconnects the ware from the kiln shelf and allows the ware to almost independently from the shelf. You could use the very short kiln posts instead of wadding if you have enough. In the bisque firing you could also use bone dry clay balls. LT
  6. Just recently went through an assignment requiring making spheres. Used several techniques. Throwing spheres is not that complicated unless you need the sphere to be thin walled. Students in class used press molds, hump moles, balloons, and hallowing out solid balls; all worked at least on sizes up to about 12 inches diameter. Drying is slower than a bowl or cylinder. Removal of the ball would be the best option. Getting oxygen into the sphere to burn the plastic is likely to be incomplete unless you deliberately force air into the sphere while firing. If the plastic is not completely burned it will likely cause problems in the glaze firing. I see two options, equally tedious. 1. cut a big hole - the 3 to 4 inch you estimated and replace or 2. cut the sphere in to two pieces and join the pieces back together. (think slicing a pieces off the top). I have seen both work, but personally lean toward option 2. I suggest that after removing the ball you make two small holes - one top and one bottom - about 1/4 or 3/8 inch size to improve drying. LT
  7. It works! Observation & comment: The position of cardboard throttle of the blower is a clue that your blower is significantly over sized. Throttling it for several hours will lead to overheating of the motor. (I've been there & done that!) Other than getting a smaller blower, adding a large throttled discharge vent to the blower outlet before connecting to the burner will allow you better control. Keep tinkering! LT
  8. Craft and Art of Clay: A Complete Potter's Handbook by Susan Peterson, or Clay : A Studio Handbook by Vince Pitelka. Either of these textbooks will be a good starting point and can carry you through a career. LT
  9. I use a pad cut from a roll of thin open weave plastic drawer liner. It helps with bat stability and wheel head cleanup. Cut to fit either the wheel head or the shape of the bats. Have both. LT
  10. I have had success using a stiff non-runny glaze to fuse pad feet to bisqued objects in the glaze firing, but only when the piece is loaded into the kiln so that gravity is working in your favor! Glaze the spot where the foot will go. Glaze the top of the foot that will connect to the piece. Add a glop of Elmer's glue to keep the foot in place while handling. The glue will burn out before the glaze starts to melt. (N.B. I fire at cone 10 in a gas kiln). If gravity isn't working for you to keep things in the proper place, the probability of making a mess is significant. LT
  11. The crack could be from picking up the pot by the rim when it is being handled after the rim has reached leather hard or drier. Rims on green and bisque ware are not normally designed to handle the stresses that occur when the pot is lifted by a single point on or near the rim. a good rule of thumb is to use two hands and lift from the bottom not the rim. LT
  12. Don't overlook the voltage drop associated with the 100+/- feet between the kiln and the main connection to the electric grid. Bigger wire gives lower voltage drop; longer runs increases the drop. If the voltage at the kiln is below the minimum voltage you may not be able to reach your target temperature. You may need larger wire than the standard guidelines for the amperage rating of the breaker since the guidelines are calculated on an assumed relatively short run length. LT
  13. It looks like a cone 10 shino glaze over a cone 10 temoku glaze fired in reduction. LT
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