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BobMagnuson

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Everything posted by BobMagnuson

  1. I can't seem to post an Excel file to this forum myself, so I'll send a copy by email to Min. I noticed that C.Banks is using Open Office. It would be interesting to hear what other folks are using to open EuCal. I only have Microsoft Excel myself.
  2. I do have an update to EuCal 1.9. Dick White was kind enough to update the % Analysis tab. Lots of the data in mine is quite old - because lots of my ingredients are quite old! Anyway, I have version 1.91. If it's Okay with Dick and Min, I'll be happy to share it. It's also fully unlocked.
  3. The evidence suggests that while ZnO is easily reduced to Zn and volatilized under reduction, once it enters the melt the loss doesn't happen, or is at least minimized. I think ZnO can enter the melt either by forming an alumino-silicate eutectic with calcium or simply by dissolving in the liquid glass. Some zinc crystal glazes have little or no calcium or alumina. In that case, EuCal isn't helpful, because the simple binary R2O:SiO2 eutectics are not included in the calculations. If calcium and alumina are present, zinc needs to be "excess to the eutectics" in order to leave enough available to form zinc silicate crystals as the melt cools.
  4. So there are indeed reduction glazes that start off with ZnO in the recipe. But Robins Clear looks like it would work fine at cone 10 without the zinc, so if some is lost due to reduction firing it would be hard to tell. Now, if there are reduction fire zinc crystal glazes, that's a different story. If zinc crystal glazes can survive reduction fire, then zinc loss due to volatilization probably isn't very important.
  5. You are correct in that, under reducing condition, zinc oxide converts to zinc metal and will volatilize around 900C. This could cause glaze immaturity due to loss of flux, or bubbles and pinholes. If reduction is started later in the fire - after the glaze has melted, there may be some protection from the volatilization, but I don't know that for sure. Does anyone out there have a successful reduction glaze recipe that includes zinc?
  6. Hello everyone. I'm the guy who put together EuCal. This Forum is new to me, so I have some catching up to do, but I'll do my best to help out where I can. No calculator can predict everything. Testing is always still needed. When using EuCal, you will find that most glazes will tolerate SOME excess SiO2 and Al2O3 before they start getting opaque. The recipe posted recently could probably be made slightly more transparent by reducing the EPK and Silica a little bit.
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