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natanata

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  1. Dear Mark, Neile! Thank you so much for your time and your thoughts on this. I found this an interesting thought: Yes, I have put cones (I have used PTC Rings) and, as I mentioned before, they showed that, yes, my kiln is firing ca. 20 C more than it shows on a screen, with a hold of 26 minutes. What I already did is lowering the temperature, BUT in this case, the exterior glaze didn't mature well, it was underfired. Bubbles where still there though. What puzzles me - is why did 2 cups out of 5 didn't have bubbles, although they were standing at the same spot, on t
  2. Thank you, Min! I just find it somehow unlogical - before no such problem occurred and glaze on exterior was firing fine. now, to solve the problem, probably, I need to fire lower, which will lead to exterior glaze be underfired. If the only reason for the bubbles is that the kiln due to aging is firing higher than it should, I should be firing lower. But what I find puzzling is - how did it all worked before, for several years, meaning, no bubbles and exterior glaze firing well. Whereas now, if I lower temperature, maybe bubbles will go, but the exterior will be underfired...
  3. Thank you all for your replies and hints.. I appreciate it so much and hope to find the answer to this. Yes, over-firing, that is also what I thought! That is why I did fire one kiln with 1220 (This porcelain can be fired up to 1250) - and the bubbles where still there, not as big, as on the photos, but still all over the pot. And the exterior glaze was then underfired... I also fired one cup with no glaze, to see if the bubbles will show up, but cup with NO glaze, had no bubbles. That is why I though that bisque firing was too short. I switched to 1 hour soaking at 1030 C bisque. But it
  4. Dear Colleagues, please help! I am puzzled – I didn't have this problem before and in the last months I have been trying to find out, why this is happening but am left clueless, as I have already tried several recommendations. Maybe you have experiences similar problems before. Problem in short: Cups come out with bubbles on the surface and in the clay. See the picture. If you break the cup, bubble is empty inside. Cups are made using Limoges porcelain, slipcasted, fired at around 1240 C. Bisque-firing at around 1020 , soaking for 1 Hour (I am using word "around" because
  5. Hello everyone! Another question from me: is it possible to cast a flat plate (without a foot) with a one-piece plaster mold? I am usually throwing a prototype with a simple white clay on a wheel, then wait until its dry enough and cast a mold, but when i tried making a plaster mold for a flat plate, plaster seemed to heavy for the clay to hold, clay got softer and caved in. As the result: the mold is with a little knob in the middle. Any advices? Thank you! Nata
  6. Mark, thanx, yesterday tried casting again using all the advices and it turned out well! actually, no, i am always mixing the porcelain powder with water as in the instruction - +45-45% water to the porcelain powder. but now it looks like it works anyway. Just another question, when you mix a new slip, how long should it sit before you pour? thanks a lot!! nata
  7. Thank you, Marc, Giselle and Hight Bridge Pottery. using all the advices i will see if i can change something next time! n
  8. when mixing the slip i wait till there are no air bubbles, i wonder if i should maybe sieve the slip every time i cast another ware, as i am always putting the rest of the slip into the main batch.
  9. Dear everyone, I am quite new to a slip casting technique. Have made several plaster molds for casting porcelain. And had some success, but recently I have noticed that some of the greenware gets tiny pinholes and then, (because some cups doesnt have it) there are SOMETIMES also pinholes on the glaze. If i got it right, those tiny pinholes are the result of air bubbles or pieces of dust in the casting slip, right? But i wonder, do those pinholes influence the glaze? I am a bit confused, because some of the porcelain cups are not having those pinholes on the glaze and some do have. The thi
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