Frits are often viewed as chemically perfect manufactured materials. But they are actually among the most process-dependent ceramic powders I use. Frits are made of recipes that must be dosed, mixed, smelted, quenched and ground. Raw material consistency is under pressure these days. And carbonates, hydrates, borates, and nitrates, which off-gas during firing, must be converted into a homogeneous glass before quenching, theoretically leaving a glass of zero LOI.
Shown here is an example of a combination of improper mixing and inadequate smelting. This melt fluidity test compares the previous good shipment, A, with this faulty one, B. The B batch was not fully reacted during manufacture (as exhibited by the foam blanket on B). But there’s more: a glaze containing 50% of this had inadequate melting. That could be chemical drift, or, inadequate batch mixing. The latter seems most likely because B was from a full two-pallet batch (the likely capacity of their smelter), from which I tested a dozen bags. Tests showed the best results at the top of the first pallet and the worst at the bottom of the second.
| Articles |
A Low Cost Tester of Glaze Melt Fluidity
Use this novel device to compare the melt fluidity of glazes and materials. Simple physical observations of the results provide a better understanding of the fired properties of your glaze (and problems you did not see before). |
| Articles |
The Chemistry, Physics and Manufacturing of Glaze Frits
A detailed discussion of the oxides and their purposes, crystallization, phase separation, thermal expansion, solubility, opacity, matteness, batching, melting. |
| Glossary |
Frit
Frits are used in ceramic glazes for a wide range of reasons. They are man-made glass powders of controlled chemistry with many advantages over raw materials. |
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