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Linchimb

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Posts posted by Linchimb

  1. How to prevent mould growing on MDF boards when pots are wrapped on them?

    in Studio Operations and Making Work

    Posted

    1 hour ago, Callie Beller Diesel said:

    MDF and moisture aren’t good companions, even if the MDF is sealed. Almost any other form of board would work better. The glue is water soluble, and the small particle size is already “bite sized” for bacteria. 

    Switching to almost any other form of plywood would be better, if you can. 

    Thanks for the suggestion, switching to plywood now…I was told that MDF absorbs moisture and let base dry quicker, maybe not meant to be wrapped. 

  2. How to prevent mould growing on MDF boards when pots are wrapped on them?

    in Studio Operations and Making Work

    Posted

    1 hour ago, oldlady said:

    why are you including the MDF inside the wrapping?  i usually see people wrapping only the pots in plastic.  that way it doesn't matter what kind of board you put it on.

    My throwing bat is MDF so just left the pot on there and thought this way it wouldn’t be distorted and I can lift it when it’s firmer. But yeah agree it would be better to just wrap in plastic. 

  4. Slip cast stoneware ripple like a naan bread after glaze firing…

    in Studio Operations and Making Work

    Posted

    On 6/22/2022 at 6:30 PM, Jeff Longtin said:

    At first blush this looks like the rippling that occurs between the top and bottom halves of a two part plate mold when the slip is too thick.  The air bubbles have no where to go so they stay trapped between the two surfaces. At some point a vacuum is created and it sucks the clay wall inward.

    I never knew it could happen until I started casting two part plate molds myself. The solution is to either thin the slip or redesign the mold?  I chose to redesign my plate molds instead. 

    Hi Jeff, thanks for your suggestion. I think this might well be the case. I use a two part mould for the plate where the main part is solid cast with an open back to pour the slip out. It often creates void and it’s not easy to have a complete fill. Maybe I need to redesign the mould…

  5. Slip cast stoneware ripple like a naan bread after glaze firing…

    in Studio Operations and Making Work

    Posted

    14 minutes ago, neilestrick said:

    Is that the firing schedule you typically use, and this sagging pot was an odd one? If so, then it's probably a thickness issue. Otherwise, it's probably over-firing. That 30 minute hold is adding heatwork equivalent to going another 1.5 cones hotter.

    yes that's my normal firing schedule. There were other pieces made from the same casting slip (from scarva) and they were fine. That's why I was wondering whether the position in the kiln also contributed to the overheating of this particular plate. Maybe I can drop the soak next time.

  9. Slip cast stoneware ripple like a naan bread after glaze firing…

    in Studio Operations and Making Work

    Posted

    Hi, has anyone experienced rippled / distorted stoneware plate after glaze firing? The plate was thinly cast using stoneware casting slip. Bisque looked fine. I placed it quite close to the kiln wall which might have caused some stress…the plate didn’t break and I’m wondering whether it will eventually break at some point or is this type of rippling kind of permanently settled. The distortion on the upper and bottom side is somehow symmetric.  
     

    thanks very much. 

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  10. Temmoku glaze shivering and crawling on stoneware

    in Clay and Glaze Chemistry

    Posted

    6 hours ago, Babs said:

    The image with the crack shows a sharp edge on inner side of lip. It may be stronger if lip compressed to a round shape, less likely to chip imo.

    Is the crack got a sharp edge or a smoother feel. Would signify a crack happening on way up or down in firing process or glaze fit so bad it is pulling your cup apart....

    I see! Thanks for the advice.

    The crack doesn't feel very sharp

  11. Temmoku glaze shivering and crawling on stoneware

    in Clay and Glaze Chemistry

    Posted

    31 minutes ago, Babs said:

     

    Is that crack sharp edged  or smooth?

    What temp. are you cracking your kiln?

    Too hot, yes your glazes wil ping on shelf.

     

    Hi, the rim is reasonably round on this one. I have seen glaze running downward and not covering rim well on some pieces with thin sharp rim. Saying that thin rim on porcelain sometimes works quite well with glaze, maybe because it’s more dense, smooth and can be vitrified (?)

    the kiln was actually opened at room temperature. I let it cool down naturally after reaching mature temperature and didn’t slow down cooling. 

  13. Temmoku glaze shivering and crawling on stoneware

    in Clay and Glaze Chemistry

    Posted

    2 hours ago, PeterH said:

    Presumably a boiling water:ice water test would increase the stresses and reveal latent flaws.
    BWIW - Boiling Water:Ice Water Glaze Fit Test
    https://digitalfire.com/test/bwiw
    ... note that for shivering you want to test cold-to-hot.
    This test subjects the clay:glaze interface to a differential thermal stress of 180F (112C†) both hold-to-cold and cold-to-hot (the former accelerates crazing and the latter shivering. This test is needed because, although ware may appear OK when first removed from the kiln, over time less-than-ideal fit will reveal itself. Compatibility between the expansions of clay and glaze are critical, not only to the integrity of the glaze layer, but also functional ware strength. Crazed glazes also provide a channel for water absorption by a porous body (creating conditions for the harboring of bacteria). Shivering glazes can drop chips of razor-sharp glaze flakes into food or drink.
    † I assume this should be 100C

    Some people use a more severe test: freezer-cold to boiling water.
    thermal shock test on mug... results
    http://www.potters.org/subject09036.htm
    ... especially Ron Roy's posts

    Thanks Peter. I just tried this ice-boiling water test and it seems fine. I might put it in the freezer and see what happens. 

  14. Temmoku glaze shivering and crawling on stoneware

    in Clay and Glaze Chemistry

    Posted

    35 minutes ago, Bill Kielb said:

    BTW, this glaze ought to melt at about cone six, is said to be matte, and it’s si:Al indicates it ought to be more matte than gloss. it’s flux ratio also places it in a range that would indicate it may not be the most durable composition. Since your glaze is very glossy, it may well be fired a bit beyond its firing range.

    Hi Bill, thanks for your reply. Actually in John Britt’s book this is a cone 10 glaze and I was thinking whether I under fired….it is very glossy. Maybe I can try a different firing schedule and temperature. 
     

    I thought crawling is the opposite of shivering and I was puzzled to see both happening at the same time. maybe the crawling was due to glaze application since temmoku type of glaze needs to be applied fairly thickly and in some areas it’s probably too thick. 

  16. How to re-tighten the bolts on Shimpo RK-55

    in Equipment Use and Repair

    Posted

    On 6/1/2022 at 2:42 PM, oldlady said:

    linchimb,  your supplier gave you very bad advice when he suggested you needed to grease any part of that new wheel.   it should be his responsibility now,    why not contact him or shimpo?

    Hi, Yes I contacted them again but they said they are getting minimal information from Shimpo. They could arrange to pick up my wheel and send to Potterycrafts who's the importer of shampoo wheels and ask them to take a look.......

  18. Temmoku glaze shivering and crawling on stoneware

    in Clay and Glaze Chemistry

    Posted

    Hi, I am testing the 'Hamada Rust' temmoku glaze on a stoneware clay body. Fired at 1250 with 30min soak. Can a glaze both crawl and shiver? On the base it looks like it crawled showing bare clay but on the rim it looks like it shivered with a small chip (although I did drop it on kitchen table, not sure if it chipped from that)....would really appreciate any suggestions for troubleshooting! The glaze pings a bit after firing on my shelf and eventually settles at some point. I haven't noticed any shivering before on slip cast bodies. 

    Here's the receipe: https://glazy.org/recipes/2967  I used Potash Feldspar instead of Custer Feldspar and Gillespie Borate instead of Gerstley Borate.

    And how do you test for shivering? On digitalfire it says shivering can be delayed, then I am wondering how would you test for delayed shivering if it can happen at any time after firing?

    Many thanks!!

     

     

     

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