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Joe_L

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About Joe_L

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    Advanced Member

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  • Gender
    Male
  • Location
    UK
  • Interests
    Learning, learning, learning....!
    Experimenting with Single Firing?

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  1. Joe_L

    Help with raw glaze bubbles

    Another possible cause might be due to raw glazing as inadequate burnout of the body can cause out-gassing through the glaze as it melts, the firing should be slow in the 600-800C zone before the glaze melts. (If you're new to raw glazing it might be worth posting your firing profile). That said, it looks like only the thicker and inside areas have the problem and the rest of the glaze is ok so I agree with the others it's likely to be a problem in the glaze department.
  2. CTM say: "As silica has a melting point around 1720oC it requires the eutectic effect of what is melting around it for it to melt at ceramic glaze firing temperatures – which is why small grain size is important to enable the other materials to surround each grain to make more localised eutectic effect. Different people like different materials – the flint, being a natural silica combined material, will melt at a quicker rate than straight quartz but is not as pure in colour. So we use the quartz 300 in our stain based glazes especially to achieve the brighter colours and as we are mixing with a fritted base glaze the quartz melts OK, we use quartz 600 in the underglazes, if we were using all materials and not fritted base glaze I would use flint to encourage easier melting."
  3. Thanks Joel, I think that's the sort of stuff what I wanted to know. Although both are silica it's useful to understand the practical implications of using the different forms available in the UK. I often use CTM but other UK suppliers also list both too.
  4. Yes I think it does mean 300mesh. Their website says "US recipes may state quartz when they mean flint." which doesn't really help me choose which one to use when they offer both. As always in ceramics, they may both be essentially silica but small differences in origin or particle size can make significant differences in results.
  5. A UK supplier lists both Flint (calcined) and Quartz 300. Which is more appropriate for mid and high fire glazes and when would I use one rather than the other? I've heard flint can have a bit more calcium so this can be taken account of in a glaze calculation program. Of course the answer is test test test but before doing lots of undirected experimentation or being led down the garden path I'd be interested in people's thoughts? Joe
  6. I threw myself a water bowl which has a deliberately sharp edge on the inside of the rim. I swipe each hand across the rim which leaves them clean and dry enough to handle tools or lift a pot off the wheelhead. Quick and simple action. The excess slip flows back into the throwing water, or sometimes accumulates in a ball just inside the rim and then I can occasionally sweep that out into my recycling bucket.
  7. Joe_L

    IMG_9848.JPG

    Thanks. I used a paper stencil cut from a real leaf as the plant was struggling this year and I didn't want to keep taking leaves (Lovage which usually grows well in our garden but we've had a very hot dry summer). I gave someone a set of soup bowls with this design.
  8. Joe_L

    Summer 2018

  9. Joe_L

    dish2.jpg

    The tenmoku must have been a bit thin as it normally produces a really good black speckled brown and this time it's just a tan brown.
  10. Joe_L

    Logging of kiln temperature to a computer?

    Whether you're doing it via a homemade controller or just using a thermocouple & logger how would you calibrate the thermocouple? You cuold compare against another thermocouple but how do you know that is calibrated? The only way I can think of is by watching cones go down while carefully heating at one of the standard rates (60C or 150C per hour).
  11. Raw Glazing. And in the background a first attempt at throwing a double walled vessel and then carving it.
  12. Joe_L

    Blistering / What Causes it?

    What clay are you using? I guess you're in the UK using those ingredients - there has been debate on here about how many UK commercial stoneware clays are actually suitable for ^6. Quite a few seem to be marketed with wide temperature ranges which may be misleading.
  13. Can't answer your underglaze question as I don't usually use it, but congratulations on the new kiln and good luck with it. Joe
  14. Joe_L

    Blowing bubbles

    Examples of pinholing.
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