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Frits are often viewed as chemically perfect manufactured materials. But they are actually among the most process-dependent ceramic powders we 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 we 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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