Same clay body: Plainsman Coffee Clay. Same glaze: MA6-C. But the mug on the left was fired in the PLC6DS schedule (normally that one does not produce this much blue, but the heavily pigmented clay brings it out). The one on the right was fired in the C6DHSC schedule. That schedule also improves the gloss and surface quality of the inside GA6-B liner glaze.

1 The original drawing in Fusion 360 (aluminum cuphead, jigger mold with bowl-outside profile, bowl mold, jigger mold case and jigger template).
2 The original bowl purchased at Ikea with the 3D printed shell of its outside contours (12% bigger).
3 The plaster form of the outside shape (created from the shell mold).
4 Printing a pair of the working mold collars (they have flanges for clamping together).
5 The collar assembly (clamped, glued and soaped).
6 The brown outside form soaped and glued to the Arborite bat using sticky clay. The collar assembly was glued down.
7 Plaster has been poured and has set.
8 The finished mold (it fit into the cuphead almost perfectly!)
9 The jigger mold inserted into the cuphead ready for use.

I applied G1947U cone 10R transparent inside and out on both bisque and bone dry ware using only a small brush. For large pieces of this shape this is better than pouring or dipping (watch the video of glazing a 35 lb bowl). This is possible because of CMC gum powder, I add 10g of it to one liter of our standard dipping glaze, blender mixing makes it possible to mix it in. The gum slows down the drying speed dramatically so there is plenty of time to brush it into place (while the wheel is turning). The gum also greatly increases the cohesion, enabling pouring it without drips, even in a long thin stream. Many pieces were done like this in our last kiln load, the evenness of coverage was the best I have ever gotten (of any technique).

The glaze recipe is GA6-C. The firing schedule is C6DHSC. The black engobe (applied inside and halfway down the outside) is L3954B. The clay body is Plainsman M370. This demonstrates how different this glaze fires on a white porcelain (bottom half outside) and a black porcelain (the engobed top half).

Gerstley Borate is being compared to Ferro Frit 3134 in a GLFL test to compare melting behavior. Clearly, these are two very different materials, the frit 3134 is obviously not a substitute for the Gerstley Borate (GB). Notice the GB shrinks to about half its original size by 1600F and then suddenly by 1650 it has exploded out of the starting gate and crossed the finish line! The frit, conversely, slowly softens through the entire 1350-1650 range and then starts down the runway between 1650 and 1700F.

The clay body is Plainsman P700. This was fired in cone 10R using the C10RPL firing schedule. The outside glaze is G2571C. The inside glaze is G1947U.

This was done on an affordable RepRap printer. The red plastic templates were drawn in Fusion 360 and sliced and printed using Simplify3D. A wooden block was used to press these cookie cutters into the clay. The plastic wrap made sticking a non-issue (and rounded the corners nicely). Commercial bottled glazes were applied to this low fire talc body by brushing (in three coats) after bisque - the rounded corners make brushing easier. The tiles were fired at cone 03. This is an old classic design that I discovered when researching Damascus tile. The toughest obstacle was learning how to use Fusion 360. It turns out that cookie cutters are a starter project for many 3D software packages, there are lots of videos on making them.

This is an example of one of John Prosser's "house mugs". They have been fracturing. Partially broken ones are spring-loaded like this. All broken pieces have black coring. Of course when thick-walled, high carbon, high iron bodies are fired without a previous bisque in heavy reduction one can expect true black coring (where Fe2O3 and CO2 react to form a body matrix hostile to even slight thermal shock). But none of these factors are present. Of course, testing could be done to bisque these higher, soak longer in the bisque, start reduction later, and oxidize longer at the end. But these measures will not likely be enough. The outer surface could be put on as an engobe over a vitreous body (but lots of work using the EBCT test would be needed because of the difference in firing shrinkage).

Stepping back consider: These black cored sections are unglazed. When iron reduces it turns black so the color black alone does not mean official black coring. When there is enough feldspar to form a good measure of vitrification (as is the case with this body) one can expect it to be suitable for light duty functional ware. Magnesia mattes like this have low thermal expansion because they contain a lot of MgO, a super low expansion flux. That puts them under compression on the body, a lot of unglazed external surface like this compounds the problem. The solution is to raise glaze expansion, something fairly easy to do in high fire. Just increase the KNaO at the expense of CaO.

This is the most complex shape known that can fit together organically. It was just discovered by mathematicians in 2023. It is easy to cookie-cut these out of clay (notice the cutter I made at the top). Placing the tiles is tricky because it is only logical to seek a pattern, but that does not work. Starting with a center tile and moving outward in a spiral around it seems to be the best way. Mathematicians are seeking to prove that placement can grow infinitely without ever repeating a pattern. Making the cookie cutter in Fusion 360 was easier than expected because the shape is built from the pie-slices that result from cutting a regular hexagon into six pieces midway across the straight sides. Because of the complexity of the shape I have found that it is best to print multiple cutters (I can do eight at a time), and stamp the shapes without using stretch wrap (letting them dry overnight in the cutters). The randomness seems confirmed in that when I piece together a few dozen tiles it is very difficult to do a count (because they are not in rows). In addition, to piece together 28 tiles requires turning eleven of them over - if there was a pattern I would expect to turn over exactly half of them. One issue: To create a setting with straight sides it appears I will need a dozen shapes.

This mug is made from a test clay body firing to about 3% porosity. While plenty strong it is capable of absorbing some water. But a thin layer of transparent glaze on the base solves that issue. I applied it by adding water to a brushing glaze version of G2926B transparent and carefully painting it on. A thin layer of silica sand on the kiln shelf completely solved the problem of sticking. And there are no sand grains stuck on the bottom of the piece either.