Report Ian Currie Test Tiles Forums? in Clay and Glaze Chemistry Posted November 16, 2017 34 minutes ago, Pieter Mostert said: Reduction makes iron a more powerful flux, so if the same is true for copper, that would explain why the SiC tiles appear more fluxed. But I don't know if this is the case. I totally agree on this point. I know iron is a flux in reduction, but I am not sure that this is the case with copper. I have never read that anywhere, but I don't fire reduction so again I could be wrong. But it doesn't account for the crazing improving slightly as more SiC is added. That would be opposite factor I would assume?