Low Fire Highly-Expansion-Adjustable Transparent
Recipe
Notes
This recipe can produce a super-transparent surface of high quality at cone 04. It has good application properties (if mixed properly, see below) and melts to a clear at cone 04-02. All of the frits are commonly available. Remember that cone 06 firing produces a poor glaze:body bond, we recommend firing cone 04 or 03 if possible (ware strength also increases greatly). This glaze can be made to fit pretty well any clay body (by adjustment in frit proportions). We recommend drop-and-hold firing, for example, the 04DSDH schedule. There are three frits: -Frit 3195 is almost a complete glaze on its own, it just needs a little kaolin. It fires slightly silky rather than completely glossy but with the addition of one of the frits below a high gloss is achieved. But it is somewhat above middle-of-the-road for thermal expansion (the 85:15 frit:clay variation, G1916J, will craze on most of our clay bodies). -Frit 3110 is super high expansion and high gloss. Blend it with Frit 3195 it to deal with shivering. -Frit 3249 is super low expansion and high gloss. Blend it with Frit 3195 to deal with crazing. In one variation we employ 30% of this and For example, to fit Plainsman Buffstone at cone 04 we find that a 55:30:15 3195:3249:Ball Clay mix works well. This frit-juggling strategy affords a wide range of adjustment for tuning the glaze fit to a body, a very important matter at low temperatures where crazing and shivering can occur with even slight thermal expansion misfit. In some situations using only Frit 3195 and ball clay might be ok. However, we recommend to 65:10:10 frit mix because the 3249 and 3110 cancel out each other's thermal expansion influence and increase the gloss of the otherwise silky 3195. The presence of 3249 also reduces boron blue issues. Stress-test the fit by subjecting a piece of thin-walled ware to boiling-water-into-ice-water (and vice versa) immersion. This will reveal a misfit that will happen with time. There can be issues with clouding. While it is well known that high boron glazes, which this is, have issues with clouding, by experience we know that this most often fires crystal clear (likely because of its unusually high silica:alumina content). Thinner application is the best way to deal with the problem. If a dipping glaze goes on too thick using normal techniques consider bisquing higher to reduce its porosity. This recipe employs #5 ball clay, a material known to produce good glaze slurries. No. 1 Glaze ball clay is another. We have made quite a few adjustments to this recipe (involving switching to kaolin as a suspender, adding more silica, opacifying, adjusting temperature), these include G1916Q2, G1916Q3, G3916, even G1916V for cone 2). To achieve even coverage it is a good idea to employ a thixotropic slurry (one that gels slightly). The 15% ball clay is plenty to suspend the slurry. But if you switch to kaolin a little bentonite might be needed.
Description
An expansion-adjustable cone 04 transparent glaze made using three common Ferro frits (low and high expansion), it produces an easy-to-use slurry.