A glaze is a thin layer of glass, fused to a clay body in the kiln. Glaze chemistry is the practice of understanding and formulating glazes in terms of the oxides they are built from, rather than treating a glaze recipe as an opaque list of raw materials to follow without knowing why it works.
Every glaze-forming oxide falls into one of three functional roles, and this wiki color-codes them consistently wherever they come up:
A single flux oxide is rarely the most efficient way to bring a glaze's melting point down. Combining two or more fluxes together, rather than relying on one alone, usually reaches a lower overall melting point than any one of them could on its own; this is a eutectic effect, and it is part of why most working glaze recipes carry a mix of alkali and alkaline-earth fluxes side by side rather than a single flux source.
Because raw materials rarely supply just one oxide, potters convert a recipe into its oxide breakdown to actually reason about it. This is what a unity formula (sometimes called a Seger formula, after 19th-century ceramist Hermann Seger) does: it normalizes the flux oxides to sum to 1 mole, so glazes of different scale and different raw materials become directly comparable. The Seger unity calculator on this wiki walks through that conversion.
Thinking in oxides lets a potter predict, rather than just observe, how a glaze will behave: whether it will be durable, whether it is likely to fit a given clay body (see crazing), and roughly what surface quality to expect. Unity-formula ratios are a modeling tool, not a hard law. Real glazes routinely succeed outside textbook ranges, and this wiki tries to flag where a rule of thumb is a useful starting estimate rather than a guarantee.