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Everything posted by Oliviine

  1. I added some photos for reference, but now have a solution. I spoke to the manufacturer, and the clay has undergone several minor reformulations, and is now 'higher in salts'. A few people have reported the issue since late last year, but a major reformulation is coming as the particular clay deposit is almost depleted. The solution to overcoming the problem is to bisque for a minimum of eight hours, pushing the temperature to 1080-1110C rather than the 1000C we use at present. Additionally, soak at top temperature for 0.5-1 hour. I'm glad I have a solution, but the manufacturer confirmed the body is now less white (amongst other things), which is a bit disappointing. Hopefully they will address that. Thank you all for the brain power...
  2. Note: This post discusses an Australian cone 10 body few will know anything about - I hope it will still be possible to discuss generalisations and brainstorm causes! Ok, my local pottery use a fine, white, 120mesh, high-fire cone 10 porcelaneous stoneware clay (Walker Ceramics PB103), this has been the primary throwing clay for at least the last decade. This year, almost every glaze firing has produced ware with some kind of surface debris of a tiny (1mm) to small (8mm) size. The debris appears on the unglazed pots, as well as scattered below every glaze, but it doesn't break the glaze surface. When you see the debris on the unglazed part of the pot, amidst the off-white clay body, the debris is bright white in colour, and looks for all the world as if you could flick it off with your nail. Sometimes the problem looks like a round pimple, other times it is completely irregular in shape. The pieces are mostly utilitarian ware, bowls, cups, plates, some decorative and sculptural. Regardless of whether the surface has been untouched from wet/trimmed at leather hard/or sanded/sponged from bone dry, the debris appears. The biscuit firing shows no issues, but almost every glaze fired piece shows symptoms (but not *always*!) After the first instance of this problem, the recycled clay anyone was using was dumped. Yet firings from the new bagged clay showed the same issue. (We were monitoring the clay being used carefully, as we were all working toward producing ware for a fundraiser.) We are quite perplexed. The group are mostly old school potters, I mention this because the internal discussion about our problem has no consensus. While there are a lot of folk with knowledge of the body, the kilns, and the process, no can agree whether the body is at fault, or something else. I am young, technically-minded, and have OCD - I want to understand and know why! While I know my clays, I know less about their kilns and firing. Is is the body? Is it dirty shelves? Is something inside the kiln deteriorating? Is it organics not burning out? We wondered about over-firing, but we did a few firings where the cone 9 did not go flat, so over-firing seems unlikely. The pottery is communal, different glazes are used, sometimes no glaze, and still the debris. We work exclusively with high-fire stoneware or porcelain. No low or mid-fire bodies are allowed inside the studio, or their electric kilns. No personal glazes, no experimentation, they risk nothing. I know little about the firing specifics, but apparently no firing programme changes have been made. I know they fire at a rise of 150°C per hour, top fire to 1280°C. I know this post is all over the place and a bit rambling, and I apologise. I just want to know if anyone has seen or heard of anything like this before? (I have enquired with the manufacturer, and am taking my dSLR to get detailed shots of the problem to send to them, when I have them I will post the images here.) Many thanks.
  3. Ha! With you on Steele, RIP. Emperor, not bad! My husband is a total metal head (Darkthrone, Morbid Angel), while I like a bit of Opeth, Katatonia, and Edge of Sanity, myself.
  4. After 12 years, and a month waiting on parts to repair my wheel, I finally got my hands back into clay and threw three good things. Pardon my French, but it felt bloody good. :)

    1. Evelyne Schoenmann

      Evelyne Schoenmann

      That's a long waiting time! Glad you are pottering again. Have fun!

  5. I'll be watching this topic because I rely on the Amaco Velvets for some pop on my stoneware. (I'm new here, and the small number firing at cone 10 has surprised me!
  6. This is a fascinating thread for me, but also frustrating because I was on Ian's site last week and this week it is gone. (All the domains associated with him are now down. Does anyone know any contact details for whomever used to maintain the sites?) Doubly frustrating is the fact that I have only just signed up here, and just begun to get back into pottery after a long hiatus. In the meantime I will find his books and begin to experiment, as I am trying to find options for a difficult-to-glaze black stoneware body.
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