URL: Richard Bideau makes his own zinc sodium frit having zero Al2O3
Click the link below to go to this page
https://crystallineceramics.co.uk/crystalline/frit-znna5515/
This enables a glaze recipe having more than double the kaolin (giving it much better application properties). However the page does not make it clear how he fuses the materials.
Related Information
ChatGPT has an opinion about making my frits:
But it missed a key factor this picture demonstrates
This picture has its own page with more detail, click here to see it.
Here is part of a ChatGPT answer that seems to confirm what I have observed in smelting material mixtures into ingots in my alumina-lined and zircon-lined slip-cast test crucibles. The upper one was fired at cone 4, the lower one at cone 6. Notice how the higher temperature has really helped to debubble the melt and produce a better glass. But it is still not melting to a transparent glass. This indicates that these small test batches are not fully reacted (all particles completely dissolved into the melt).
The upper picture reveals a potentially serious issue with making frits in a crucible: Frothing. When LOI gas evolution overlaps with the formation of a sticky melt, the batch can swell into foam. That foam impedes heat transfer, and the viscous melt can retain the bubbles. That being said, gas bubbles generated during melting can assist mixing as they rise through the glass. So it is a balance: Bubbles yes, foam no. Crucible capacity must accommodate the batch during reaction—not just the finished ingot. In industry, they use the term "generous crucible headspace and suitable refractory secondary containment" to refer to learning how much to fill to avoid overflow and how to mitigate this when it does happen. In a frit batch containing significant carbonates and hydrates, it could be that even a half-full crucible could overflow!
Alumina-lined crucible frit ingot test:
The first of multiple milestones to making your own frit
This picture has its own page with more detail, click here to see it.
To melt a frit batch, the first challenge is the crucible and release from it. These disposable crucibles were cast from L4404A refractory slip. The front one has an alumina-based liner L3693E. Without the liner, the ingot in the back is inseparable from the crucible wall. But in the other, the alumina has remained as a powder and can be cleaned off the ingot, leaving almost no residue. This test was done at cone 04, so only a tiny amount of Al2O3 is taken into solution in the melt.
Why would a potter consider doing this? Problems with commercial frit availability and consistency are motivating some to investigate making their own. But there are more challenges. Commercial frit manufacturers control melting conditions to produce a homogeneous glass, then crash-cool it to limit crystallization and facilitate grinding. Their furnaces ensure heat distribution throughout the batch (a real challenge in a crucible in a pottery kiln). But some frit compositions are considerably more resistant to grinding; a studio ball mill might not be up to the task. Producers also melt frits at cone 13-20 (a potter frit-firing to cone 10, what a producer smelts to cone 15, risks producing a partially reacted mixture of glass and undissolved solids, rather than the homogeneous frit intended by the formulation). And their furnaces are in no danger of cracking during firing. And they have expertise to formulate and test for low water solubility (yes, glass having an unstable chemistry can dissolve in water). They also have tight control over the particle size of the finished powder. They also have equipment to control dust during crushing and grinding (remember - that the dust is tiny angular glass shards!).
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