These 10g balls GBMF test balls were fired far lower than typical bisque; notice how many of them are already melting well! Frit 3602 is lead bisilicate. Maybe you always thought lead was the best melter. But it got "smoked" by the Fusion FZ-16 high-zinc, high-boron, zero-alumina frit! However, notice the FZ-16 is crazing badly; that is a problem for many applications using this high KNaO frit. Want to get some of this frit for pottery? You can't; Fusion Ceramics doesn't want to handle retail sales of smaller quantities.
Notice that, at this low temperature, each frit has a distinctive melt fingerprint that makes it recognizable.
Notice that the common North American pottery frits on the bottom row: 3195, 3249, 3124, 3110 (and 3134 in the second row) fire distinctly differently. Notice Fusion F69. It looks like 3249 because it is a substitute for it! F-75 is a substitute for 3110 (sharing the same melting pattern but having different micro-bubble clouding).

This picture has its own page with more detail, click here to see it.
This demonstrates the amazing melt behaviour of lead-as-a-flux for ceramic glazes. Not only does it melt early, but it softens slowly over a 300F range of temperatures before it goes off the end of the runway on this GLFL test. Then, when fired 200F hotter than that, it remains a stable, clear and uncrazed glass. Beginning around 1750F, this becomes a transparent glaze, by itself.

This picture has its own page with more detail, click here to see it.
This melt flow tester demonstrates the beautiful crystal-clear glass this zinc frit creates by 1700F. It fits this porcelain without crazing, even though it is very thick and high in sodium (the high zinc and boron are countering it to keep the thermal expansion down). It runs off the end of the runway around 1600F on this GLFL test, rivalling lead bisilicate. This is a more concentrated boron source than even Gerstley Borate. Everything about this material screams “ultra gloss”. What a material to build a fluid-melt reactive super-glaze on!

This picture has its own page with more detail, click here to see it.
These 10-gram GBMF test balls were melted at 1850F.
| Ferro | Frit 3134 | Frit 3124 | Frit 3195 | Frit 3110 | Frit 3249 |
|---|---|---|---|---|---|
| MgO | 12.2 | ||||
| CaO | 19.5 | 14.3 | 11.4 | 6.3 | 3.5 |
| Na2O | 10.1 | 6.4 | 5.7 | 15.2 | |
| Al2O3 | 2 | 10 | 12 | 3.7 | 13.3 |
| B2O3 | 22.8 | 13.7 | 22.6 | 2.6 | 28.9 |
| K2O | 0.7 | 2.4 | |||
| SiO2 | 45.6 | 54.9 | 48.3 | 69.8 | 42.1 |
| COE | 9.5 | 8 | 7 | 10 | 4 |
| Si:Al Ratio | 38.7:1 | 9.3:1 | 6.8:1 | 32:1 | 5.4:1 |
| R2O:RO Ratio | 0.3:0.7 | 0.3:0.7 | 0.3:0.7 | 0.7:0.3 | |
| Tests |
Glaze Melt Fluidity - Ball Test
A test where a 10-gram ball of dried glaze is fired on a porcelain tile to study its melt flow, surface character, bubble retention and surface tension. |
| Temperatures | Comparison of frit melts at 1700F (926-) |
| Materials |
Frit B325
|
| Materials |
Frit LA-300
|
| Materials |
Ferro Frit 3249
A magnesia borosilicate frit. Very low thermal expansion. Invaluable for increasing the MgO in glazes (to prevent crazing and create matteness). Low melting. |
| Materials |
Ferro Frit 3195
A commonly available calcium borosilicate frit. It is glaze-like, needing only a kaolin addition to create a low-temperature semi-glossy glaze. |
| Materials |
Ferro Frit 3124
A commonly available calcium borosilicate frit. It is glaze-like, needing only a kaolin addition to create a low-temperature glossy glaze. |
| Materials |
Ferro Frit 3110
High sodium, high thermal expansion low boron frit. A super-feldspar in clay bodies. Melts at very low temperatures. Useful to make crackle glazes. |
| Materials |
Fusion Frit F-524
A low fire base glaze, add 10% kaolin, adjust thermal expansion using other frits. |
| Materials |
Fusion Frit F-75
High sodium, high thermal expansion low boron frit. An equivalent of Ferro Frit 3110. |
| Materials |
Fusion Frit F-69
A magnesia borosilicate frit having very low thermal expansion and melting point. Commonly used as a substitute for Ferro frit 3249. |
| Materials |
Ferro Frit 3134
A frit with 23% B2O3. The most common of frits used in pottery in North America. Around the world, other companies make frits of equivalent chemistry. |
| Materials |
Fusion Frit FZ-164
|
| Materials |
Fusion Frit F-38
High strontium low alumina borosilicate flux. |
| Materials |
Ferro Frit 3602
A lead bisilicate frit with 2.5% alumina oxide. |
| Materials |
Fusion Frit FZ-16
The champion in our frit melt-off competitition. This frit showcases the amazing fluxing power of boron and zinc working together. It is 15.5% ZnO. |
![]() PayPal | No tracking, No ads, No paywall, No transient content! Just organized, concise information constantly updated and improved. Was this helpful? Consider supporting me. |
Buy me a coffee and we can talk