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RuthB

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About RuthB

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    Advanced Member

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  • Location
    Charleston, SC
  • Interests
    Clay, Glazes, Kilns, Firing, Marketing, Teaching

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  1. The students themselves are the closest contact for transmission, to their classmates and the clay. The virus dies when it dries out. So dry all clay before slaking for recycling. If you can figure out how to work it without contamination, make every student responsible for their own recycling. No mixing of clay. Social distancing and other CDC recommendations will likely be required in schools, so separate all the work areas. It’s possible that certain activities will not be allowed to resume for quite a while, working with clay in a group setting being one of them. Or scale back the work considerably. A thorough examination of the possibilities of pinch pots? Everyone be well.
  2. Thanks Neil, as a repair tech seeing lots of kilns, you have a large sample. But, in my practice, leaning has not caused any problems for this kiln or the ware. It is 17 years old, and as you can see is an L&L. No brick wear. I don’t make a lot of plates, so maybe that’s why. My brain must be a bit fuzzy right now because usually I place them to span an angle so that only 2 points touch the sides. I am the only one who loads the kiln and I fire very slowly to 1700F, giving time for temp to equalize and burn out any unfriendlies in the clay. Before anyone says I should be firing to 06, more years have passed than I care to admit. It works for me.
  3. I fire plates plates by leaning the first one against the wall of the kiln, then continue with more plates. I’m in the middle of loading a dinnerware set. I’ll send a pic shortly
  4. My 8 year old Shimpo was getting slower and slower. I called Shimpo after trying to adjust the potentiometer. That’s when I learned that it needed a new control board for $317.00. I mostly handbuild so the wheel was not used daily. I did not know that the capacitors on the control board are like a battery and the wheel needs to run to keep them charged. Sitting idle decreases their life span. Am I the only one not aware of this? Is this so with all the newer wheels? My 40 year old year old Brent has been repaired once. I bought the Shimpo for the quiet Thanks to all. Ruth
  5. Great idea! I have made bats from the interfacing used in sewing, available from a fabric store. It's available in various thickness and stiffnesses. I then brush porcelain slip on both sides. Great bats, easy to peel off, take no room to store.
  6. I'm thinking the same thing. The clay does stick to the bat and there may be some drag possibly increased by the wooden tools and the dry clay causing tension in the base. It sounds like it doesn't always happen, but often enough to be a drag ( no pun intended). As Rae suggests doing a little trimming on the back would remove this clay before it becomes a problem in drying. You may want to add 1/8" in thickness to your platters so that you have enough clay to trim off. Alternatively, don't throw them at all. Cut a piece the desired size from a slab and flip on to the bat. Attach to the wheel head and add a coil to the edge and throw just the rim. Wire off and dry on slats.
  7. Have you made any videos of the roller tools in use?
  8. Your point is well taken, re squirting clay. To clarify, when opening, I'm pressing from both the top and side of the opening, so the clay can't squirt anywhere.
  9. Compression and alignment go hand in hand. Compressing the base aligns the particles through the base. Hamer and Hamer (The Potter's Dictionary of Materials and Technique) have some interesting points to make about the difference in drying shrinkage vertically through the thickness of the base as opposed to horizontal shrinkage across the base because the particles are aligned differently in walls vs. the base. Somehow, there is uneven shrinkage from the rim to the center happening during drying in these plates. As you wrote, it's always helpful to see how a piece is thrown when figuring out a solution. I think it would be helpful to see a video of the throwing of these pieces. Is there a lip to these plates? How is it made?
  10. The root of cracks such as these is found in the opening process. The clay and the metal wheel head have a terrific attraction for each other. If you opened the clay by starting at the center and pulling out to the edge, clay directly in contact with the wheel head the clay does not move uniformly from the center. The clay particles in the base will not be lined up as they are in the wall at the completion of throwing. The shrinkage will be uneven from the sides/edges to the center resulting in the cracks such as yours. To insure that the clay particles are lined up in the base as they are in the walls, extra attention needs to be given to the base by moving your hands from the edge back towards the center so that the base is subjected to similar pressure to the walls. I also am careful not to open by pulling the mound out from the center. I gradually enlarge the opening by pressing straight down on the edge so that the clay moves outward little by little. The base is also compressed with each move. I finish by going back and forth on the base several times, moving toward the center more than outward. Alternatively, you can leave a goodly amount of clay under the base to be wired off, removing the unaligned clay before making the foot. I prefer the first method. Hamer and Hamer has a great discussion of cracking in their Potter's Dictionary. Let me know if my explanation needs more explaining. Ruth PS. Any reasonable even drying will not cause these cracks.
  11. Babs

    Nice to read your words again RuthB

  12. Plates, platters, tiles can be stacked on edge leaning against the kiln wall, avoiding the element. Or a kiln post can be leaned first as a buffer. In this way, quite a few can be leaned, including leaning stacks against stacks Cracking problems are reduced as well. Check YouTube for some good videos on stacking flat pieces in this way all around the kiln wall, staggering stack against stack. Use the top shelf if post height is a issue. I stack anything that reasonably sits in or on top of another, bowls, mugs, etc. Three pieces max, unless it’s rim to rim or foot to foot. This guideline must have made its way into my DNA by now.
  13. I’ll make it this weekend and let you know when it’s up
  14. Plates can be subjected to a lot of stress during making that doesn’t show up until the firings. Plates that have been made by mostly flattening the clay with an outward motion are most susceptible to cracking, especially if they do not have a foot. There is a tremendous attraction between the clay and the metal wheel head and clay that has been stretched out against the wheel head will be subjected to competing forces. You’re moving the top part of the clay outward while the bottom is doing its best to stick to the wheel. Leaving enough clay to cut a foot on the bottom gets rid of the stressed clay. It also helps to move the hands back inward toward the center at least as much as you move them outward. Uneven drying can also cause cracking. Dry slowly, so that the rim does not dry before the center of the plate. A donut of plastic wrap around the rim will help. And make sure the plate is of even thickness. Thick and thin areas will dry unevenly. Slabs should be turned and flipped during the making to prevent similar cracking issues. Ruth Ballou
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