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).

This is 50g of sodium bentonite in 1 gallon of water (~0.5% concentration). Sodium bentonite can swell up to 10–15 times its dry volume, creating a thixotropic gel that really resists mixing. With a better propeller, faster mixer, hot water, slow addition, etc. we might be able to achieve 1% (or ~100g/gallon). Apparently, with industrial high-energy mixing in special vessels, 4% is possible for drilling muds. They can even go beyond that using shear pumps, ribbon blenders, or paddle mixers to achieve a pseudo-plastic non-Newtonian gel. 4% - that seems impossible to me! Why does all this matter? Some say that a gel like this can be added to a settling glaze to fix it. Is that true? Not really. Here is why. Our typical imperial gallon of dipping glaze contains 3500g powder (US gallon 2800g). At least 1% bentonite is needed to make any difference, that is 28-35g. If you have a great mixer and can make a slurry having double the concentration of this one, 100g/gallon, then to deliver the minimum bentonite for a gallon of the glaze would require 1/3 gallon of this! While the added bentonite might help somewhat, the effects of all that extra water will cancel the benefits.

This award-winning couple are-all in on crystal glazes. They have learned that success is about data. A lot of data. Thousands of pictures, hundreds of firing schedules, hundreds of recipes, endless notes all come together in the growth of crystals like these! Notice the clear background, no micro-crystals fogging it up. Notice that two fundamentally different types of crystals are being grown. Not to be ignored is the throwing skill it takes to make a porcelain piece like this, these are not small pieces.

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.

The clay is Plainsman 3B. Without processing, other than grinding to 42 mesh, it fires as shown on the left (at cone 6, 8, 9, 10 and 10R bottom to top). The speckle and bloating are caused by impurity iron-bearing particles and others having an LOI (they decompose and produce gases that cause the bloats). These particles make up a small percentage, they can be removed by sieving to produce a body of porcelain-strength and density. This natural porcelain fully vitrifies by cone 6 (the middle bar). Only about 5% of the material was removed to produce this amazing product (which I call MNP).

These two sets of SHAB test bars are fired from coldest to hottest (bottom to top) through the range from cone 04 up to cone 4. The graph shows the decreasing porosities and increasing shrinkages as temperature rises. Note the terra cotta reaches maximum shrinkage and minimum porosity at 2000°F (above which it begins expanding and melting). The talc body, by contrast, slowly matures, reaching a minimum porosity of 7% at 2150°F. It thus only sinters, never reaching a state of anywhere near the maturity and strength of the terra cotta. Clearly, the latter is not only high in iron oxide, but also in fluxes (like K2O, MgO, Na2O, CaO, etc) - these are responsible for how fast it vitrifies. The point where maximum fired strength is produced is the third bar up, 1970°F on the graph. However, there are multiple issues: Ware will warp in the kiln, the terra cotta red color has been lost and LOI gases of decomposition will disrupt glazes (with bubbles, blisters and pinholes). The most practical temperature is the second bar up, adequate density, good color, better quality glaze surfaces. The talc body? Although it fires to poor maturity across the range, it has one trump card: It provides a good base for glazes, producing bright colors and no bubbles.