Opening the kiln after a glaze firing is like opening a Christmas present, there’s massive excitement mixed with a lot of apprehension. Will it be the perfect book you have always longed to read or the dreaded novelty slippers that are impossible to walk in!

Unfortunately on opening the kiln this morning I was faced with the worst case of novelty slippers ever.  Almost every piece was damaged in some way, seemingly affected by some weird volcanic like eruptions on the surface together with in some cases large air pockets trapped in the walls of the pieces.  This isn’t the first nasty surprise I’ve had either, my last kiln load was similarly affected and now I’m desperate for answers.  I have trawled the internet for possible causes; the work had not dried sufficiently, the bisque was fired too quickly or maybe it was down to carbon coring (a new one for me), was the kiln packed too tightly and therefore there wasn’t enough oxygen present during the firing.

I reflected on all of these points and so when I put the kiln on for a second time I tried to address all these possibilities and act accordingly but alas the results are exactly the same.


So now I turn to you………to anyone who’s out there and may be able to help.  With Christmas orders to fulfil, this may be the difference between a new mug in someone’s stocking or some bath salts!

10 thoughts on “HELP!

  1. I sympathise! Looks like bloating, essentially caused by firing too quickly ( for that particular clay, or batch of clay, which might have an excess of impurities).

    1. Thanks for the feedback Pete, I am certainly getting the feeling that the clay is the issue. It may be time to change brand.

      1. Yes – I had something very similar and unaccountable a few years back in a glaze firing. I hadn’t changed my firing pattern, and could only put it down to the clay. Maybe that particular batch had an excess of organic matter (which might not have been visible as such). These days I fire very slowly – it avoids a host of potential problems, & even if it costs slightly more in electricity I probably recoup that in less kiln failures.

  2. Hi Jo,
    Pete has suggested something similar to what I was about to say in that it could be down to a batch of dodgy clay. I encountered something similar this summer. About a third of my firings cracked. I hadn’t changed method or materials, I just couldn’t account for it. I carried on with new clay (casting slip in my case) and things came right again. It was most odd and the only thing I could think was that I had a contaminated batch. It’s very dispiriting when this happens, I hope you manage to sort it out. Best of luck!

      1. I meant to continue!
        It’s so frustrating when the clay looks perfectly ok until the very last stage, after all the hard work has been done!
        I’m certainly reluctant to continue using clay from the the same batch ( I have another 3 bags) so maybe it’s time to try out some new clay bodies!
        Just discovered your fabulous work, it’s great to see and hear what other people are up to.

  3. Oh no, I hope you manage to get this sorted out quickly Jo. I can’t offer any helpful advice but know how demoralising this kind of thing can be. Fingers crossed the next kiln full is perfect. Good luck.

    1. Thanks for your concern Juliet. Things seem to be pointing to the clay so hopefully when I get a new delivery I’ll be back on track.

  4. Hi Jo, whilst I’m relieved the clay you’re having problems with isn’t one of ours, I thought you would appreciate some technical notes on bloating that I’ve managed to dig out. I’ve emailed them to you. I’ve also sent via courier some samples of the three white stonewares we discussed – let us know what you think! 🙂

    1. Becky, I really appreciate your help and the technical notes you sent. I’ll look forward to the samples arriving and let you know how I get on.
      Thanks again.

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