This spoon was dipped into a ceramic dipping engobe, L3954B. It contains no CMC gum, it was only flocculated using powdered Epsom salts. Without the Epsom salts, the engobe runs off, leaving only a film. But, when turned into a thixotropic slurry, it stays on the spoon in an even layer (as a gel), then hardens as it dewaters (left) and finally dries completely (right). With no cracks! It also fires to cone 03 with no cracks. Of course, if this were fired high enough, it would begin to shrink, crack, crawl, melt and then craze, ceasing to be an engobe. Of course, special low-expansion frits and additives and mixing, preparation and application techniques make enamels, which do melt, possible for metals.

This is M340 stoneware fired to cone 6 using the C6DHSC schedule. The L3954B engobe fires deep black (it has 10% Mason 6600 black stain). The engobe was applied by pouring and dipping at leather hard stage (inside and partway down the outside). After bisque firing, the piece was glazed inside using the base GA6-B Alberta Slip amber base. The outside glaze is Alberta Slip Rutile Blue GA6-C (you are seeing it on the bare buff body near the bottoms and over the black clay surface on the uppers).

The blue line is a crystal glaze firing schedule. While it reaches the same temperature as a typical glaze firing (purple line) it is different in how it does so. Notice key differences (while cone 10 is most common for this type of glaze, we will discuss theoretical differences in a cone 6 version):
-The steep climb: Crystallization needs a clean bubble-free melt, no lingering in temperature zones where they might start prematurely.
-The steep drop to 2000F: Crystals typically grow during a long soak in the 1900–2000°F nucleation zone.
-If the temperature is simply held steady at 1950°F only one type and size of crystal would form, likely smaller and crowding out others. The ups and downs are about manipulating the thermodynamics and kinetics of crystal formation — nudging new crystals to form or existing ones to grow differently.
-Cooling and then raising the temperature in the nucleation zone can re-dissolve smaller crystals or unstable nuclei. Then, cooling again encourages new crystal nucleation, rejuvenates existing ones or even changes the pattern of their growth.
-In the upper range of the nucleation zone, faster diffusion produces larger, more spread-out crystals. In the lower range, slower diffusion produces smaller, tighter crystals or detail-rich growth.
-Crash-cool to finish: Drop melt viscosity quickly to halt all crystal formation - this preserves a clean background and prevents blurring of crystal edges.
Crystalline firings are about precision and timing: Get in fast, melt everything, play within the range where crystals want to grow to get the type, distribution and size you want - and then get out. It is not difficult to see why crystal glazers may do thousands of test firings to discover the curve that produces what they want. The nucleation zone depends on firing temperature and glaze chemistry, testing is likewise required to discover it. Meticulous record keeping is critical to success; not surprisingly, many crystal glazes do it in an account at insight-live.com.

The evolution of the quality and aesthetics of your work, and even your ability to cut costs, are stunted when you depend too much on others (e.g. for firing, for premixed glazes). This mug is a good example of tests I need to do. This is G3933, made by adding iron oxide, rutile and tin oxide to a 75:25 blend of our base matte and glossy glazes (G2926B and G2934).
-It is crawling at some of the sharp angles of the incised decoration, would a little CMC gum fix this?
-Would an 80:20 blend of the two glazes give a little more matteness?
-Our red-burning body gives better color at cone 5, would this glaze be richer and more matte on it in the C5DHSC slow cool schedule?
-I want to test increases in the rutile (for variegation), iron (for better color) and granular manganese (for more speckle).
-Would a Ravenscrag Slip base glaze be a better host for the rutile, iron and tin?
Having a small test kiln puts all of these changes on my radar. An account at insight-live.com to document everything well brings it all together.

The challenge: Create a 3D printed case mold that incorporates a plaster section just for the finished surface.
Top right: The secret is M3 brass threaded inserts in pyramid-shaped 3D-printed anchors (I have just pressed them into the 4.4mm dia, 10mm deep, -3 degree tapered holes using a soldering iron). These brass/plaster pyramids embed into the plaster to provide a threaded hole that M3 bolts can screw into.
Upper left: We made a cross-section CAD drawing of a three-piece demonstration mold (upper left). The top plate has holes for the M3 bolts, air escape and natch clips and recesses for clamps to hold a 3D shell, with flanges, in place (not shown).
Lower left: The anchors have been screwed onto the upper plate.
Center left: The plaster was poured, and over-filled, then the top plate, with anchors, pressed down on top of it. After set, the plate was unscrewed and removed.
Bottom right: The plaster section has been reattached and natch inserts and anchors put in place. The plaster was not sanded or prepared, this is a demo.
What is this all about? A full master case mold, utilizing this technique, coming soon.

This is the most complex shape known that can fit together organically, without a pattern (dubbed the Einstein tile, it was discovered by mathematicians in 2023). It has six sides of 1 unit length, six of 1÷1.73205080757 and one side measuring twice the latter. Placing the tiles is tricky because it is only logical to seek a pattern, but there is none. One method is to start with a center tile and move outward in a spiral, being ready to backtrack and place them upside down when a piece cannot be fit. The tile shape is a product of connecting four identical irregular pentagons - each made by cutting a regular hexagon into three pieces. To achieve the maximum precision, 3D print multiple cookie cutters and let them stiffen and shrink in the cutters. To round the upper corners use stretch wrap) when stamping (print cutters in both orientations if doing this). Tiling a floor or wall will present issues with the number of edge tiles that need to be cut. However, cutting at least some custom edge shapes is practical because only 90 and 120 degree angles are needed.

G2926S reduces the thermal expansion of the popular G2926B (a durable, crystal clear, easy-to-use general purpose cone 6 base glaze for stoneware and porcelain). However, some porcelains (e.g. these Plainsman P300 mugs) need the lower thermal expansion this offers (to avoid crazing). This recipe adjusts "B" chemistry by adding low-expansion MgO at the expense of high-expansion KNaO (while maintaining gloss). This is more expensive to make (because it calls for Frit 3249 or equivalent) - use it if G2926B (with 325 silica) fails an IWCT test for crazing. These mugs were fired using the PLC6DS firing schedule, the S glaze was opacified with 10% Zircopax and the outside glazes are G2934Y silky matte with added stains. Need to reduce COE even further? Try G2926J.

This inside glaze is G2926B (on Plainsman M340). It is capable of firing glassy smooth, crystal clear and un-crazed even on coarse stonewares. Watch the video 📹 to see the four unusual things we do to get reliable glazes like this. But the recipe is only part of getting success. Mixing it as a thixotropic slurry is another. And the firing schedule: Look closely at the two glazed tiles. The bottom one, although fired lower (cone 5.5) was slow cooled using the C5DHSC schedule - note how much smoother the glass is (the upper one was fired to cone 6 using the PLC6DS schedule).

The outside is a floating blue, GA6-C. These are a dime a dozen but a good transparent is priceless. Did you know that the outside glaze can be made from the inside one by simply adding 2:4:1 iron oxide:rutile:cobalt oxide? This glaze can be stained, opacified and variegated in an infinite number of ways. And it is adjustable (e.g. lower thermal expansion, lower or higher melting).

This is a "badlands" slope in the Frenchman river valley. The valley exposes the "Whitemud Formation" in many places (clearly visible here part way down on the left). Two surface mines of Plainsman Clays are nearby, in a place where lower-lying rolling hills leave much less over-burden to remove. These materials were laid down as marine sediments during the Cretaceous period. The skeleton of the world's largest T.Rex, dubbed "Scotty", was found 50km east of here (in the layers just above the Whitemuds). Where are the layers of Scotty's ancestors from the Jurassic period? Straight down 1 kilometer! And another kilometer to bedrock!

These are the original cone 6 Perkins Studio Clear (left) beside our fritted version (right). You cannot just substitute a frit for Gerstley Borate (GB), they have very different chemistries. But, using the calculation tools in my account at insight-live.com, I compensated for the differences by juggling other materials in the recipe. I even upped the Al2O3 and SiO2 a little on the belief they would dissolve in the more active melt the frit would create. I was right - a melt-flow GLFL test comparison (inset left) shows that the GB version flows less. Using this on ware exhibited another issue (after doing a IWCT test): Crazing. The very good melt flow on my G2926A fritted version is thus good news: It can accept more silica - the more silica, the more durable and craze resistant it will be. How much did it take? 10% more! That ultimately became the recipe for our standard G2926B cone 6 transparent.