Glaze Calculator
Glaze calculator - see Files at the top of the page to download it.
Glazes are generally most stable when as much of the glaze material as possible can form tetrahedra and be incorporated into the glaze matrix. Materials like SiO2 can do this naturally as they have a charge of +4, but the intermediates with form R2O3 only have a charge of +3, so can only link to 3 oxygens, forming a flat triangular instead of a tetrahedron.
To get round this, they pair up with an alkali (preferably an alkali metal) to give them the extra charge, and so form a tetrahedron. So this requires an adequate amount of alkalis in the glaze. Too much alkali and it acts as a network modifier, weakening the glaze matrix. Not enough alkali and you get things like phase separation (e.g. boron), crystallisation (e.g. aluminium or alkali earth matt glazes), or the intermediates acting as modifiers.
The arithmetic for this is a bit messy, but I've started putting this into a spreadsheet for you to use. It is an early release, so lots still to do, but future releases will come here periodically. It is written for the current version of Excel for Windows, but ill probably work on other Excel compatible spreadsheets.
The video below runs through how to use it (this assumes some knowledge of the associated glaze chemistry, as given in the Science pages).