Can a cone 6 functional glaze having only whiting and feldspar melt enough?

Monday 7th November 2016

This flow test compares the base and base-plus-iron version of a popular CM recipe called "Tenmoku Cone 6" (20% whiting, 35% Custer feldspar, 15% Ball Clay and 30% silica, 10% iron oxide). Although iron is not a flux in oxidation, it appears to be doing exactly that here (that flow is just bubbling its way down the runway, the white one also fires to a glassy surface on ware). It looks melted in the tray on the right but notice how easily it is scratching on the tile (lower left). This demonstrates that looks can be deceiving. Cone 6 functional glazes always have some percentage of a power flux (like boron, lithia, zinc), otherwise they just do not melt into a hard glass. Maybe a glaze looks melted, but it has poor durability.

Pages that reference this post in the Digitalfire Reference Database:

Glossy blacks are best made adding a black stain to a quality base transparent, Borate, Melting Temperature, Cutlery Marking, Glaze Durability

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