Monthly Tech-Tip | No tracking! No ads! |
These test frit ingots were melted at cone 04 and slow-cooled. We used cast crucibles made from L4404A refractory slip. The front one has an alumina oxide liner of L3693E. Without the liner, the lead bisilicate ingot in the back is inseparable from the body. But with the liner (front), it easily breaks away. The alumina has remained as a powder and can be easily cleaned off the ingot leaving almost no residue. Frit manufacturers crash-cool frit batches by quenching them in water, this one was slow-cooled, we are hoping that will be the key to passing a lead leaching test.
I asked ChatGPT this question and got a very thoughtful answer that seems to confirm what I have observed in smelting material mixtures into ingots in alumina and zircon lined slip cast crucibles. The mixtures are melting well in the test crucibles (the upper one was fired at cone 4, the lower one at cone 6). But there are issues. There does appear to be phase separations. And bubble froth at the top. For some compositions alumina works better as a liner, for others zircon. We are getting closer to trying larger multi-kilogram batches and ball milling so time will tell.
Buy me a coffee and we can talk