Multiple batches of fired test bars, organized by temperature, have already been weighed and measured (the weights and lengths are written on the sides of the bars). Each batch is accompanied by the cones from the firing in the test kiln (these influence how the temperature is recorded and adjustments to kiln firing schedules). Since we are working on many runs, tests and projects at any given time, these tests pile up rapidly. And they generate a lot of SHAB test data that needs to be input into your Insight-live.com account promptly.

Plastic natches are cast into plaster molds to provide a durable and good-fitting interlock between pieces. The traditional self-interlocking 3/8" or 9.5 mm (nipple diameter) one has not proven suitable for mold making based on 3D printing. Our solution is a four-part system. To use it, your 3D printed mold shells only need matched 13.5mm holes.
-13.5mm holes in 3D printed case molds are all that is needed to adapt to these.
-3D printing case and block molds necessitates pouring plaster and rubber into shells with planar mating surfaces downward (they must sit flat on the table). The thin flanges on the clips cause minimal issues.
-Casting an embed into a mold enables gluing (or friction fitting) a natch or a spacer inside.
-The use of embeds permits flat mating surfaces - these can be sanded (for better flatness and fit). They also allow replacing natches if they get broken (assuming friction fit).
-A set of four interlocks (4 embeds, 4 clips, 2 spacers, 2 natches) weighs 8.7g.
Our drawing shows the measurements we use. 3D printing is precise enough that the inside dimension of the embed is the same as the outside of the natch shoulder, yet the natch fits. The same good fit happens with the clip and embed and the natch nipple and spacer (although it is necessary to chamfer the bottom corners and bevel the top corners of the spacer for better insert).
Some dimension changes may be needed to fine-tune for printing in your circumstances.

-Size of mixing container: 1L per 1000g of plaster.
-To determine the amount of plaster and water needed our normal process is to counterbalance the mold and fill it with water to get the cc volume, in this case 2000. Then use the glazy.org plaster calculator for the amounts of plaster and water needed. But this time I just used the gram/weight as the amount of plaster, 2000g. I derived the water, 1400g, according to the 70/100 ratio recommended by USG (it was 200g less plaster and was sufficient).
-Using a 4-minute soak and a good propeller mixer there is no need to sprinkle the plaster in.
-Make sure no plaster is hanging on sides of the mixing container after soak.
-Mix with a whirlpool shallow enough that it does not suck air but deep enough that it is pulling bubbles up to the surface.
-Make sure the mold is strong enough not to split at the bottom and is a strong shape that will not bow out. 3D print it so the artifacts are at the top. For PLA mold soap is not normally needed.
-Make sure the mold is sitting on a very flat surface.
-We had to apply tape to the bottom flat surface to make sure it is watertight.
-Pour the plaster into the mold in a steady stream that does not pull in bubbles.
-Remove using a heat gun when the plaster is set.

Stains can work surprisingly well in matte base glazes like the DIY G2934 recipe. The glass is less transparent and so varying thicknesses do not produce as much variation in tint as glossy bases do. Notice how low many of the stain percentages are here, yet most of the colors are bright. We tested 6600, 6350, 6300, 6021 and 6404 overnight in lemon juice, they all passed leach-free. The 6385 is an error, it should be purple (that being said, do not use it, it is ugly in this base). And chrome-tin pink and maroon stains do not develop the color (e.g. 6006). But our G1214Z1 CaO-matte comes to the rescue, it both works better with some stains and has a more crystal matte surface. The degree-of-matteness of both can be tuned by cooling speed and blending in some G2926B glossy base. You can mix any of these into brushing or dipping glazes.

This glaze, G2926B, is our main glossy base recipe. Stains are a much better choice for coloring it than raw metal oxides. Other than the great colors they produce here, there are a number of things worth noticing. Stains are potent; the percentages needed are normally much less than for metal oxides. Staining a transparent glaze produces a transparent color, it is more intense where the laydown is thicker - this is often desirable in highlighting contours and designs. For pastel shades, add an opacifier (e.g. 5-10% Zircopax, more stain might be needed to maintain the color intensity). The chrome-tin maroon 6006 does not develop well in this base (alternatives are G2916F or G1214M). The 6020 manganese alumina pink is also not developing here (it is a body stain). Caution is required with inclusion stains (like #6021). Bubbling, as is happening here, is common - this can be mitigated by adding 1-2% Zircopax. And it’s easy to turn any of these into brushing or dipping glazes.

The outside glaze is G2934Y cone 6 black. I use the C6DHSC slow cool firing schedule to get this degree of matteness in the black. The body is the natural MNP (Mother Nature's Porcelain), it vitrifies to zero porosity around cone 4 (yet is stable to cone 8). At cone 6 it produces incredibly strong ware and works well with these two glazes. The inside liner glaze is GA6-B (made using real Albany Slip rather than Alberta Slip in this case). Although the melt characteristics of these two glazes are so different they can be applied to meet in a perfect line at the rims of pieces. Food safety labelling is not what you think it is - do liner glazing to be safe.

Dipping glazes peel like this because they contain clay and shrink as they dry (the fact that all of them don't do this is actually amazing). Success is a matter of the shrinkage being low enough, the drying being fast enough, the layer being thin enough, the bisque being absorbent enough, and the bond with the bisque being good enough. Glazes with high clay content, thick applications or multi-layering are the main offenders. Thixotropic slurries apply most evenly and are least likely to go on too thick. Dipping glazes having 15-20% kaolin or ball clay are easiest to slurry up and have the best application and drying properties. Mixing base layers as first-coat dipping glazes is also important.

The problem with this piece: The addition of 7.5% bentonite to make up for the otherwise low raw clay content in the recipe produced a recipe that does not pass a sanity check. When that was replaced with kaolin it worked. There is a crowbar approach to fix these without any other changes: Add CMC gum (e.g. 1%) to make them brushing glazes.

G1214Z1 is a popular cone 6 calcium matte glaze recipe. It has very high melt fluidity, enabling a fine grained crystalline matte surface to develop during cooling. A potter was steered to this recipe after finding that G2934 magnesia matte fired too variegated when stained blue. However, her first effort with this failed a leaching test. She had a secret weapon: An account at Insight-live.com, where recipes and their calculated oxide formulas can be compared side-by-side. Leaching glazes are most often runny because they contain excessive fluxing oxides. She simply increased the SiO2, it is the glass that makes up the lion's share of all glazes (higher amounts of it characterize glossy glazes). Al2O3 couples with it to improve durability (and the Si:Al ratio is a factor in the degree of matteness). With an accompanying small increase in the B2O3, the magic glass:flux that makes most cone 6 glazes possible, the got the result on the right. The good news: It passed the GLLE test for leaching. There is a lesson here: She had to compromise the degree of matteness a little to get the food safe product. A benefit is that it is also less prone to cutlery marking. Happily, it turned out that much less blue stain was needed.

Dolomite is a key material for glazes, especially mattes. We were forced to adopt a new brand and needed confidence it was equivalent. Three tests were done to compare the old long-time-use material (IMASCO Sirdar) with a new one (LHoist Dolowhite). The first melt flow tester compares them in a very high dolomite cone 6 recipe formulated for this purpose; the new material runs just slightly more. The second tester is uses the G2934 cone 6 MgO matte recipe with 5% black stain; the new material runs a little less here. The third test is the high dolomite glaze on a dark burning clay to see the translucency and compare the surface character. They are very close. These three gave us the confidence to proceed.

These two Plainsman M370 test mugs were fired at cone 6, the left one with G2934 matte glaze, the right one with G2934Y4 matte. They look and feel identical in the hand. The two glazes have the same chemistry. But they employ different materials to source that chemistry. The secret of of the matteness is high MgO (magnesia content). In the glaze on the left MgO is sourced by dolomite, a lot of it. The glaze on the right sources it from a special frit, Ferro 3249. The impact of this difference is visible in the melt fluidity tester, the fritted one is melting and flowing much better. On other clays, especially stonewares, the G2934 can have a dry surface that cutlery marks. Thicker applications make it worse. But the Y version exhibits no such issues. Its mattness, durability, cleanability and hardness are so good that it is being used in floor tile.