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Oldmuddy

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  1. Like
    Oldmuddy reacted to clay lover in Weight/size Charts?   
    what about developing yur own chart, based on how you throw now.  When I get a new form the size and shape I want, I record in a binder the weight of clay used, the size I open to and the wall and finished rim size.  then when I want to go back to it it's way easier.  When I started I wrote the size clay I had used on the bats of the freshly thrown pieces, then measured after they were glazed.  I developed from there.v
  2. Like
    Oldmuddy reacted to neilestrick in Mug Sizes   
    1 1/4# = 12-14oz., porcelain, with a tall trimmed foot. This one:
     

     
    1# = 11-12oz, porcelain, without a tall foot. This one:
     



  3. Like
    Oldmuddy reacted to Diane Puckett in Weight/size Charts?   
    Hopper's book, Functional Pottery has that info and is in general a wonder resource.
  4. Like
    Oldmuddy reacted to Min in Hairline Cracks During Bisque Firing- Why?   
    The book Curt mentioned, Frank Hamer's the Potters  Dictionary of  Materials and Techniques is really good and has a thorough explanation of cracks in greenware, bisque, glaze firing. You can read the entire section on cracks and their causes in a Google book preview here.  If you can't post a picture perhaps this excerpt will help.
  5. Like
    Oldmuddy reacted to neilestrick in Hairline Cracks During Bisque Firing- Why?   
    If you're adding a foot ring to the bottoms of the bowls while the bowl is leather hard, the foot ring will shrink more than the bowl, and can put stress on it. Just one possibility. What direction do the cracks go- up and down or around?
  6. Like
    Oldmuddy reacted to neilestrick in Hairline Cracks During Bisque Firing- Why?   
    Did you add a foot ring to the bowls? How dry was the bowl when you added the foot? Post some pictures if you can.
  7. Like
    Oldmuddy reacted to liambesaw in Hairline Cracks During Bisque Firing- Why?   
    Oh wow, I'm surprised I haven't run into that. I do all of those things haha.  I've cracked bisqueware by heating it too fast though so I understand how that could happen when firing green
  8. Like
    Oldmuddy reacted to liambesaw in Hairline Cracks During Bisque Firing- Why?   
    If you're compressing your bottoms well and not lettting water sit in the bottom, i would blame the clay.  I've never heard of a firing process introducing cracks, my bisque casualties have always been massive and violent.  If it were from stacking improperly I'd expect the crack to form on the rim instead of the bottom.  If your facility has been recycling clay it might be losing too many fines and needs them replaced (glazenerd's recipe is I think 60% ball clay, 20% silica, 20% feldspar @ 1 cup per gallon of reclaim)
    I'd definitely ask the professor though, it's probably something they've seen before and can remedy.
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