|Monthly Tech-Tip |
Alternate Names: F3124
This is a USA pottery frit. Ferro now calls it Frit 3124-2.
This borosilicate frit is high in calcium. It melts are very low temperatures and among the most useful of all common frits because of its glaze-like balanced chemistry. This frit has a chemistry somewhat similar to 3134 (the latter adds CaO, Na2O and B2O3 at the expense of all the Al2O3 and some SiO2.
Its stated intention is a calcium boron source for partially fritted glazes for wall tile and pottery, also in lead bisilicate dinnerware glazes in the cone 3-5 range. However, within pottery circles, like frit 3195 this frit is almost a complete glaze at low temperatures (requiring only a 10-20% addition of kaolin to suspend it). It has a medium thermal expansion and fits most bodies. However if glazes shiver some of this can be traded for Frit 3110. If they craze some can be substituted for Frit 3249. Frit 3124 is often added to glazes to make them melt lower, this works well because it is quite balanced already as a glaze, the net effect of adding it is to increase the boron content without overly disrupting the balance of other oxides.
Since the chemistry is high in CaO, it will affect browns and iron oxide colors.
G2934B is a popular recipe and there has been alarm recently because of the difficulty in getting the Ferro frit. This motivated us to get a supply of the Fusion equivalent, F-19. We have done much testing in glazes and with melt fluidity tests like this and so far it is looking good.
On paper, Fusion F-19 has a very similar chemistry to 3124. However, as can be seen here, it is flowing a little more and appears to have a lower surface tension. The glass is also more transparent and the entrained bubbles are bigger. The differences could be partly to Fusion using a different set of raw materials to source the chemistry or differences in their smelting process.
This chart compares the decompositional gassing behavior of six materials as they are heated through the range 500-1700F. These materials are common in ceramic glazes, it is amazing that some can lose 40%, or even 50%, of their weight on firing. For example, 100 grams of calcium carbonate will generate 45 grams of CO2! This chart is a reminder that some late gassers overlap early melters. That is a problem. The LOI (% weight loss) of these materials can affect your glazes (causing bubbles, blisters, pinholes, crawling). Notice talc: It is not finished gassing until 1650F, yet many glazes have already begun melting by then (especially fritted ones). Even Gerstley Borate, a raw material, is beginning to melt while talc is barely finished gassing. And, there are lots of others that also create gases as they decompose during glaze melting (e.g. clays, carbonates, dioxides).
These two boron frits (Ferro 3124 left, 3134 right) have almost the same chemistry. But there is one difference: The one on the right has no Al2O3, the one on the left has 10%. Alumina plays an important role (as an oxide that builds the glass) in stiffening the melt, giving it body and lowering its thermal expansion, you can see that in the way these flow when melting at 1800F. The frit on the right is invaluable where the glaze needs clay to suspend it (because the clay can supply the Al2O3). The frit on the left is better when the glaze already has plenty of clay, so it supplies the Al2O3. Of course, you need to be able to do the chemistry to figure out how to substitute these for each other because it involves changing the silica and kaolin amounts in the recipe also.
Fired at 350F/hr to 1450F and held for 15 minutes. Frit 3134 is still expanding. 3602 is blasting out of the gate, taking the lead. F75 is starting to flow.
Fired at 350F/hr to 1500F and held for 15 minutes. Frit 3134 is still expanding. 3602 and FZ16 are really starting to move. 3195, F38 and F15 are softening.
Fired at 350F/hr to 1550F and held for 15 minutes. Frit 3134 is still expanding. 3602 and FZ16 are going to be off-ramp by next firing.
Fired at 350F/hr to 1650F and held for 15 minutes. FZ16 has turned crystal clear and spread out across the runway (has low surface tension). Frit 3110 has so much surface tension that the flow can be lifted off the tester. Since 1600F Gerstley Borate has gone from unmelted to passing all the rest!
Fired at 350F/hr to 1700F and held for 15 minutes. 3110 is finally starting to move. 3134 also (being full of bubbles). Gerstley Borate has turned almost transparent. 3195 is looking very well behaved compared to most others, forming a bubble free glass of high surface tension (F15 and F524 are starting to do the same).
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.
The Fusion one is flowing a little more. And it has larger bubbles, so Fusion must be using a different set of raw materials to source the chemistry (materials that either have higher LOI or decompose to produce gases later in the firing). They do not supply the chemistry of Frit F621/19 and it is not shown on their website in 2021. But they recommended it to us as substitute candidate for Ferro Frit 3124.
Fired at 350F/hr to 1800F and held for 15 minutes (I already did firings from 1300F-1750F in 50 degree increments, all of them are visible in the parent project). Frit 3110, 3134, 3195, F75 have run all the way down. All of the frits have softened and melted slowly over a range of temperatures (hundreds of degrees). By contrast, Gerstley Borate, the only raw material here, suddenly melted and flowed right over the cliff (between 1600 and1650)! But not before Frit 3602 and FZ16 had done so earlier. Frit 3249 is just starting to soften but F69 (the Fusion Frits equivalent) is a little ahead of it. LA300 and Frit 3124 are starting also. F524, F38, F15 will all be over the end by the next firing. The melt surface tension is evident by the way in which the melts spread out or hold together.
Fired at 350F/hr to 1350F and held for 15 minutes. Some are still burning off carbon (which seems strange). The two FZ16s are starting to move. Frit 3134 is expanding. 3602 is also starting to melt.
Fired at 350F/hr to 1300F and held for 15 minutes. Some are still burning off carbon (which seems strange). There are two early leaders: Ferro frit 3110 and Fusion frit F75 are starting to deform (they have almost the same chemistry). Amazingly, these two frits have low boron, they rely on high soda as the flux.
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.
Fired at 1850. Notice that Frit 3195 is melting earlier. By 1950F, they appear much more similar. Melting earlier can be a disadvantage, it means that gases still escaping as materials in the body and glaze decompose get trapped in the glass matrix. But if the glaze melts later, these have more time to burn away. Glazes that have a lower B2O3 content will melt later, frit 3195 has 23% while Frit 3124 only has 14%).
A cone 6 firing. The glaze on the left has a B2O3 molar content of 0.54 whereas the one on the right has 0.64 (other oxide levels are the same). This is triple the typical amount of boron in a cone 6 glaze, the result is obvious: High melt fluidity for both. But G3904A has a significant characteristic that is different: The flow is more transparent because of the lower micro-bubble population. It's melt is less viscous, that enables the bubbles to pass, exit and the surface to heal. Why don't all glazes use more boron? Cost. Frits are expensive and they are the best source of boron. There is also a cost to durability (although mitigated when there is plenty of Al2O3 and SiO2 present, as is the case here). These recipes were part of an interesting project to fix a recipe where the potter mistakenly used Frit 3134 instead of 3124 when mixing a large batch of glaze. I calculated how much kaolin and silica to add to bring the chemistry back into line with the original. This was possible because frit 3134 chemistry is an approximate oxide-subset of 3124. The resultant glaze is potentially better than the original.
These were 10g balls melted using our GBMF test. Frit 3602 is lead bisilicate. But it got "smoked" by the Fusion FZ-16 high-zinc, high-boron zero-alumina! Maybe you always thought lead was the best melter. That it produced the most transparent, crystal clear glass. But that is not what we see here. Notice something else: Each frit has a melt-fingerprint. When two are similar we can see it immediately.
16 GBMF tests on a slab of grogged clay. Kiln fired at 108F/hr for last 100 degrees F and held for 15 minutes.
These are higher temperature frits. 10 gram balls were melted on to this tile.
16 GBMF tests on a slab of grogged clay. Kiln fired at 108F/hr for last 100 degrees F and held for 15 minutes.
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).
|Materials||Fusion Frit F621/19|
|Materials||Ferro Frit 4124|
|Materials||Frit RCG 2430|
|Materials||Hommel Frit 90|
|Materials||Pemco Frit P-311|
|Materials||Hommel Frit 378A|
|Materials||Fusion Frit F-19|
|Materials||General Frit GF-113|
|Materials||PotteryCrafts Frit P3124|
|Materials||Potclays Frit 2272|
|Materials||Ferro Frit 3134|
Ferro Pottery Frits 2008
|Co-efficient of Linear Expansion||7.94|
|Frit Melting Range (C)||1600-1750F|