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Dick White

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  1. Dick White

    Advice on Kiln I Found

    It looks to be in reasonably good shape. The cone supports for the kiln sitter are missing, but easily replaced. There is a chunk missing from the bottom edge of the bricks, but that's not the end of the world either. While the stated dimensions may be correct for overall size, the interior dimensions are 18" wide *meaning the widest diameter piece you can fire is about 15" on the top shelf with no obstructing posts, or 10" on a lower shelf allowing for the space taken up by the posts. The total inside height is about 23", but the center ring is an unpowered blank ring just to create a bit more height inside. However, that means the heating power of the kiln is diluted a bit, so it might have some trouble reaching a full cone 10 despite the official maximum rating. Mid-fire should be okay. It is a manually controlled kiln with a kiln sitter safety shutoff device. You will need to manually turn up the heating controls periodically during a firing, and personally shut it off when the cone packs inside (and visible through a peephole) indicate it is done. The electrical wattage (6400W) means you will need to install a 40 amp circuit for it. (Theoretically, it draws less than 30 amps, but the electric code requires a circuit with a 25% safety margin, for which the next size up is 40A). If the kiln comes with the shelves shown in the picture (and hopefully a selection of posts too), $200 is a very good price, if you are willing to learn how to fire a kiln without an electronic controller.
  2. Dick White

    Fixing a plaster mold?

    Well, actually, Cascamite in the EU is a synthetic plastic resin glue (urea formaldehyde), similar to Weldwood Plastic Resin glue in the US. It is a powder that is mixed with water, but when cured is water resistant. "White glues" are PVA (poly vinyl acetate), one common brand is Elmer's. Yellow carpenter's wood glues are also PVA, but with other resins added to improve their performance in woodworking applications, such as open time, tack, and water/weather resistance. The yellow color is simply a dye to distinguish it from plain white PVA glues. Casein glues are made from milk proteins, and are water resistant. Elmer's School Glue at one time was a casein-based glue, but now is a PVA glue.
  3. I have done something like that (but don't have any pictures) with a white clay body, a clear glaze (to show the white body as background) and Amaco LUG-1 black liquid underglaze quickly splashed onto the still-wet clear glaze. When the glaze melts in the firing, the droplet of underglaze will flow readily. It has to be the LUG liquid underglaze series, the Velvet or other gelled underglazes can't be splashed on.
  4. Daniel, welcome to the zoo. I will address your questions in the order asked, though the answers are more relevant in the reverse order. 1) Hydrocal (and other plasters) will not stick to the clay mold. The clay can be peeled right out and any remaining residue can be washed off. 2) Hydrocal is a plaster-like material. It does not dry in the mold like casting slip, allowing you to pour out an excess from the interior of the mold. Rather, it sets by chemical action and that action is simultaneous throughout the wet plaster. The whole thing will harden all at once.
  5. Clay by itself does not explode. Water turning to steam (at 100C/212F) can cause a clay vessel to explode. A raw clay object that has not dried will explode from the steam and fragments will be found throughout the kiln. Once the water has dried, it will not explode. There will be a time at around 900F that a very thick piece of clay will break due to creation of new water at the time of ceramic conversion of the clay, but only if the exterior surfaces are sufficiently hotter and the surface has sintered and sealed over, trapping the new water deep inside. Even then, it is not an explosion, merely a spalling of chunks off the side. If a bisqued piece, which is still absorbent, is saturated with water (such as from glazing) and fired before it dries, another steam explosion will occur. But if it has been successfully glaze fired, it is improbable that you can saturate enough water into the now-vitrified ceramic that it would explode if it was fired yet again. It will very likely crack from the steam, but probably not a spectacular explosion as you seem to want.
  6. Dick White

    Hudson River Clay

    The axes on the Stull chart are the molar UMF numbers for Si (X axis) and Al (Y axis) respectively.
  7. Dick White

    changing specific gravity of glazes

    Different river...
  8. Dick White

    changing specific gravity of glazes

    I use a #4 Ford cup, bought from the big river in South America, and I find the correct viscosity for dipping glazes is around 6-7 seconds. S.G. for my dipping glazes is typically between 1.4 and 1.5. Adjust the S.G. first, then flocculate or deflocculate as needed to adjust viscosity. S.G. is a physical adjustment whereas viscosity is a chemical adjustment. Stabilize the physical adjustment first, then make the chemical adjustment.
  9. Dick White

    Hand-building advice

    It is my understanding and experience that clay warps for 2 reasons - 1) Uneven drying results in the clay shrinking more on the drier side, putting tension on the still-moist side that has not yet shrunk as much. It may seem to straighten out, but it comes back in the firing. 2) Stretching and bending during the process of making the piece may seem to be put back in place, but it returns in the firing. With wheel thrown work, an errant hand movement may cause a bulge in the cylinder that is difficult to repair. For thrown and altered work, the warping is intentional. With handbuilt slabs, even gently "peeling " it up off the table to move it will put a slight bend in the slab. Moist slab pieces are still flexible and will bulge and distort slightly during assembly. You can smooth it back into place, but the warp will return. Conversely, if the slab is moved by flipping from one flat surface to another, and the cut pieces are allowed to firm up before assembly, the pieces can be handled without bending and any intentional curvature can be added once without the back and forth of trying to put an undesired bulge back where it belongs.
  10. Dick White

    Selling an old L&L kiln - advice on value

    It is unique, but not odd. It is just a standard 3-section 29" manual kiln with 2 extra powered rings stacked on top, with the usual box for the control switches expanded for all 5 sections. Because the controls and sections are designed with plug-in pigtails for the power, one can add/remove sections as desired. The analog pyrometer has a rotary selector switch so you can click through the 5 thermocouples to maintain accurate zone control with the infinite switches. Some thoughts about the electric specs - 100 amps to a single circuit is a lot, would require a direct wired connection, no such plug exists. 208v is typically a commercial service, even as single phase; residential service is usually 240v single phase.
  11. Dick White

    Hudson River Clay

    Huh? Somebody called me? Yup, MTS. A crystalline glaze would not even be on the Stull chart. Alumina UMF levels are typically below 0.05 and Stull's shaded area stops at 0.1. Silica UMF as a number by itself is typically too low at 1.5 to 2.0, but with the non-existent alumina, the SI ratio is at a mind-bogling 35-50 compared to the 7 in a "normal glaze". So we MTS out of it and leave it sit molten until the zinc gets tired. And not that it really matters, a nit I noticed in one of the quotes... The Glazemaster program was written by John Hesselberth, not John Britt. John H and Ron Roy together wrote the book Mastering Cone 6 Glazes, but John wrote the computer program. Glazemaster is my go-to calc program and I have way too much data in my copy if anybody needs some. Also willing to answer how-to questions from other users.
  12. Dick White

    What the heck is MAGIC WATER

    Soda ash and Arm and Hammer Super Washing Soda from the laundry aisle in the grocery store are approximately the same. Both are sodium carbonate, though the washing soda has some of the hydrous form while pure soda ash should be the anhydrous form. Another source of soda ash is a pool supply store - pH Up is a typical brand of pool soda ash. Since the specter of vinegar now has crept into the picture, there is a chemical difference between the two approaches. Magic water is an alkaline (sodium) based deflocculant which opens the pores of the clay to make the joined pieces squish together more thoroughly. Vinegar is an acidic flocculant which makes the surfaces of the joined pieces glue together better. Mixing these methods will cause them to neutralize each other.
  13. Dick White

    What the heck is MAGIC WATER

    It's magic. The recipe was developed by Lana Wilson - 1 gallon of water, 3 tablespoons liquid sodium silicate, and 1 1/2 teaspoons of soda ash. (It would take me a lifetime to use a gallon, so I adjust it proportionately for several cups at a time.) It is a mild deflocculant which causes the surface of the clay at the particle level to open up a bit so that the parts to be joined will interlock together better.
  14. Dick White

    How to measure out chemicals for glazing

    I have found when mixing glazes that a good starting point of how much water to use is 1 liter of water per 1000g of dry batch. After it is mixed and has slaked for a day, you can add a bit more water if needed until it is at the proper consistency. A second observation from my experience, you don't want to make full buckets of glaze - they will spill and splash over the top when you mix and stir. The max I put in 5 gallon buckets is a 7500g batch. This is my practice, others may do it differently.
  15. Dick White

    Skutt Kiln transformer hum

    Check that the mechanical mounting of the transformer and/or control board is tight to the chassis frame. There may be some vibration between the metal parts that is alleviated by displacing the board ever so slightly when you press that secret sweet spot?
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