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Cratering Raku Glaze


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#1 centered

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Posted 12 December 2010 - 07:13 PM

Hi I was wondering why my raku glaze looks like huge craters and easily flakes off. when i raku fire should i bring the temperature up slowly and hold it there for some time? do you think this may help? Or... did i apply the glaze too thick? i found that my kiln will get up to 1850 degrees within 10-15 minutes. this was my first firing and will do many more test firings soon. thanks

#2 Marcia Selsor

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Posted 12 December 2010 - 09:08 PM

When firing by vision information rather than pyrometer, the glaze does through stages easily observed visually.
I always equated the crater state as the "pancake ready to flip" then shortly after that , the glaze fluxes and turns to glistening shimmering
wet look, which means pull it out of the kiln. Put a small ^06 in there to see how close the pyrometer is reading.
Your crater stage is under fired. Maybe your pyrometer is off. Also go a little slower. 10-15 minute for the first firing may be a little fast. Fire visually if you are using shiny glazes. Get to the shimmering wet stage visually.
Marcia

#3 Seasoned Warrior

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Posted 12 December 2010 - 10:52 PM

When firing by vision information rather than pyrometer, the glaze does through stages easily observed visually.
I always equated the crater state as the "pancake ready to flip" then shortly after that , the glaze fluxes and turns to glistening shimmering
wet look, which means pull it out of the kiln. Put a small ^06 in there to see how close the pyrometer is reading.
Your crater stage is under fired. Maybe your pyrometer is off. Also go a little slower. 10-15 minute for the first firing may be a little fast. Fire visually if you are using shiny glazes. Get to the shimmering wet stage visually.
Marcia


Just like Marcia said. I prefer to use visual conditions to know if I'm up to temperature. That shimmering, once seen is hard to forget and tells you the glaze is "a point" . It's been my eperience that the visual clues are actually more accurate than using instrumentation and a whole lot faster. Good luck,

Regards,
Charles




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