|Monthly Tech-Tip |
I used Veegum to form 10 gram GBMF test balls and fired them at cone 08 (1700F). Frits melt really well, they do not gas and they have chemistries we cannot get from raw materials. These contain boron (B2O3), it is magic, a low expansion super-melter. Frit 3124 (glossy) and 3195 (silky matte) are balanced-chemistry bases (just add 10-15% kaolin for a cone 04 glaze, or more silica+kaolin to go higher). Consider Frit 3110 a man-made low-Al2O3 super feldspar. Its high-sodium makes it high thermal expansion. It works in bodies is great to make glazes that shiver. The high-MgO Frit 3249 (for the abrasives industry) has a very-low expansion, it is great for fixing crazing glazes. Frit 3134 is similar to 3124 but without Al2O3. Use it where the glaze does not need more Al2O3 (e.g. already have enough clay). It is no accident that these are used by potters in North America, they complement each other well (equivalents are made around the world by others). The Gerstley Borate is a natural source of boron (with issues frits do not have).
Five common North American Ferro Frits fired at 1850F on alumina tiles (each started as a 10 gram GBMF test ball and flattened during the firing). At this temperature, the differences in the degree of melting are more evident that at 1950F. The degree of melting corresponds mainly to the percentage of B2O3 present. However Frit 3134 is the runaway leader because it contains no Al2O3 to stabilize the melt. Frit 3110 is an exception, it has low boron but very high sodium.
It is made from 85% Ferro Frit 3134, 7.5% kaolin and 7.5% silica. While not obvious from the recipe, one look at the chemistry of this (as displayed when you enter a recipe into your account at insight-live.com) will show very low Al2O3. Frit 3134 has almost no Al2O3, yet it is an essential component of functional glazes (for durability, resistance to crystallization, stability during firing). The kaolin is the only contributor of Al2O3 and there is only a little. A simple fix would be to use Ferro Frit 3124 instead, remove the silica and increase the kaolin to 15.
Can't get frit 3134 in early 2021? You are not alone. Don't listen to people who say you can just replace frit 3134 with 3124 in glaze recipes. That is wrong. Frit 3124 has five times the amount of Al2O3 (the second most important oxide in glazes) and half the amount of boron (the main melter). The glaze chemistry approach is much better, and easier than you think. To be able to do it you need two other Ferro frits, 3110 (or Fusion F-75) and 3195 (Fusion F-2). As it turns out, Frit 3195 is more important than is 3124! A key goal in the way I do this was to end up with at least 15% kaolin (to suspend the slurry). I have chosen three types of recipes to demonstrate. Dealing with each requires a unique approach. Two of the calculations produce improved slurry properties and one a recipe of significantly lower cost. I made a video demonstrating substituting Frit 3134, see the link below. If you have a recipe that needs this, get an insight-live.com account, enter it there and I can help you do the calculation.
Frits are used in ceramic glazes for a wide range of reasons. They are man-made materials of controlled chemistry with many advantages or raw materials.
Calculated Thermal Expansion
The thermal expansion of a glaze can be predicted (relatively) and adjusted using simple glaze chemistry. Body expansion cannot be calculated.
Most ceramic glazes contain B2O3 as the main melter. This oxide is supplied by great variety of frits, thousands of which are available around the world.
Glaze chemistry is the study of how the oxide chemistry of glazes relates to the way they fire. It accounts for color, surface, hardness, texturem, melting temperature, thermal expansion, etc.
Shivering is a ceramic glaze defect that results in tiny flakes of glaze peeling off edges of ceramic ware. It happens because the thermal expansion of the body is too much higher than the glaze.
Understanding your transparent glaze and learning how to adjust its melt fluidity, thermal expansion, color response, etc is a base on which to build all your other glazes.
|Materials||Ferro Frit 3110|
|Materials||Ferro Frit 3124|
|Materials||Ferro Frit 3134|
|Materials||Ferro Frit 3195|
|Materials||Ferro Frit 3249|
|Tests||Glaze Melt Fluidity - Ball Test|
|Oxides||B2O3 - Boric Oxide|
Ask the right questions to analyse the real cause of glaze shivering. Do not just treat the symptoms, the real cause is thermal expansion mismatch with the body.
|Temperatures||Gerstley Borate Melts Suddenly (1600F-1650F)|
|Temperatures||Common frits begin melting (1400F-)|
G1916Q - Low Fire Highly-Expansion-Adjustable Transparent
An expansion-adjustable cone 04-02 transparent glaze made using three common Ferro frits (low and high expansion), it produces an easy-to-use slurry.
Where do I start in understanding glazes?
Break your addiction to online recipes that don't work. Get control. Learn why glazes fire as they do. Why each material is used. Some chemistry. How to create perfect dipping and drying properties. Be empowered. Adjust recipes with issues rather than sta