The fluxes that we use do the heavy lifting for getting our materials to melt in the kiln. One of or a combination of Lithium, Sodium and Potassium are the fluxes in almost every single clay and glaze that we use. We can see why they are so effective for melting in their reactions with water in this video.
We don't use them in this raw state, Instead we use them in an oxide form Li2O, Na2O, K20. This keeps them from being explosive as they have already oxidized (which is what this video shows happening). But it is this very reactive nature that gets our Clay and Glazes melting.
Since we are talking about Glaze Calc, don't forget that there is still space available for my Glaze Calc class "Glaze of our Lives", June 27th -July 1st, at Truro Center for the Arts at Castle Hill in beautiful Truro, MA.