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LinR

is this glaze food safe?

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I'm going to have pots in a once/year wood firing.  Ben Bates Oribe Green Cone 9-13 was  given in a CM this past year and looks very interesting but I am wondering with 6% Copper carbonate if it would be food safe fired between cone 10 - 12?

recipe is:

Bone ash                      2%

Talc                                  9%

Whiting                      23%

Custer feldspar      31%

EPK                                11%

Silica                               24%

add:  Copper  Carb  6%

Thanks for any help you can offer.

 

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Lots of debate on this forum as to whether or not copper leaching is an issue or not. Here is one of the discussions that is worth reading. 

To make a stable glaze there are "limits" for the necessary amounts of silica and alumina (and other oxides) for glazes. If you fall far below the limits for silica and alumina the other oxides in your glaze are more prone to leaching out of the glaze. Have a look at column one in the chart below, it is the formula for your glaze (without the copper), now have a look at the last column, it is the "target limits" from Green & Cooper for a cone 10 glaze. 

637548230_ScreenShot2018-05-05at8_34_14AM.png.e45bee941f595a204bbe939ecc64463e.png

 

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