pre-Glazes

A pre-glaze is a mixture of materials which have the potential to form a glaze if it is fired to an appropriate
cone. It contains the required oxides (i.e. some fluxes together with alumina and silica), and has an empirical
formula within some reasonable limits.

Before a pre-glaze can melt into a glaze, it must remain on the pot, attached to it in such a manner that
when it melts it can form a uniform coat over the entire pot. That is, it becomes a glaze when
it's demonstrated to coat a pot, melt, and stay on the pot throughout the entire process.

Many pre-glazes are "not a glaze at any temperature." If before the pre-glaze reaches a temperature at which
melting begins, it cracks apart and/or separates from the pot, its melting behavior is irrelevant. Conversely, if the
pre-glaze suddenly melts with such low viscosity that it flows like water off the pot and there is no
temperature at which it will melt and remain on the pot, it is also clearly "not a glaze at any temperature."

A thorough understanding of when melt (i.e., sintering) occurs is an important part of glaze development and
these tests are meant increase understanding of the process.

two glazes which separate from the test tile