Using an engobe is the best way to make a black clay surface. Left is a version of L4768E this is not the best way to make black, but the one most use (and what Plainsman Clays does with Coffee Clay). It is the darkest that it is practical to make (using the hyper-red burning C-Red clay as a base and adding umber). This method is far better than adding umber (or manganese) to a white or buff burning clay because only half as much is needed, which cuts in half issues that come with these pigments. The L4768F mug base looks black when viewed beside buff and red burning bodies, and it is black enough to host the GA6-B honey-colored glaze to produce a deep glossy jet black glazed surface. But the black body color on the right is the star! First, it is not a body, it is just a thin veneer of stained porcelain engobe, a far less expensive solution than trying to stain the whole body black. That being said, so people need a totally black body. Even in these cases it is being to make your own. Try using the L4053B recipe as a starter. Get a plaster table and a propeller mixer and you will be unstoppable!

Goldart (left) compared to Plainsman Midstone (right). Goldart is a buff and vitreous stoneware at cone 10R. These are fired at cone 7, 8, 10 oxidation and 10 reduction (bottom to top). Soluble salts in the Goldart impart a darker coloration to the reduction fired bar). The Midstone has some coarser particles that make for larger speckles in reduction.

These two AI dotors are really with the plan! Everyone knows the calming effect pottery can have, no wonder it is recommended over chemicals as a way to deal with stress. Pottery acts as a form of meditation, creative therapy, and stress relief all rolled into one. The MidJourney.com AI doctor on the right is perfecting his skills at home before recommending them to patients. His six-fingered hands doubtless improve quality of the ware. The Google Gemini doctor on the left is very serious about the potential of pottery, having integrated her potter's wheel right into her office desk. She is a very clean thrower also. Pottery offers a unique combination of benefits that can be therapeutic for those dealing with stress and depression:

-The process of working with clay demands focus and presence. The tactile nature of the material and the repetitive motions can help quiet the mind and induce a "flow state" where you lose track of time and worries.
-Pottery enables you to channel feelings into something tangible and beautiful, fostering a sense of accomplishment and control.
-Creative activities can lower stress hormones and the physical act of kneading and shaping clay can release tension.
-Successfully creating a piece of pottery, no matter how simple, can boost confidence and provide a sense of pride.
-Joining a pottery class or group can provide a sense of community and belonging, reducing feelings of isolation.

It is about using consumer 3D printers (and mostly PLA filament) and professional CAD software (now available for DIYers) to make plaster molds for ceramics. It prioritizes being green, learning to formulate and use your own casting bodies and glazes. Here is what you'll gain:

-Step-by-step guides.
-A constant emphasis on using as little filament and producing as little waste as possible.
-Insights into the cost-effectiveness and simplicity of these tools.
-Motivation to build your own repository of designs, constantly build better skills to improve them and leverage rapid redesign cycles and efficient production.
-Learn to formulate, mix, test and adjust your own casting bodies.

Whether you're a curious hobbyist or a seasoned mold maker, this group will show you why these technologies are the future. It's easier, more affordable, and more rewarding than you think. Let’s mold the possibilities together!

This black engobe, L3954F, is on a cone 6 buff stoneware (at leather hard stage). It contains only 7.5% Mason 6600 black stain. How is that possible? Why do people add so much more to their underglazes? Because this recipe has been tuned to have the same degree of maturity as the body - it therefore fires totally opaque. This contrasts with underglaze/engobe recipes containing significant frit, among other issues, their vitreous nature renders them translucent. Thus, up to 40% stain is needed to crowbar their opacity enough to intensify color. And a thicker application (that carries other issues).

Notice how thinly and evenly this is applied. This was possible because of another key factor: The slurry was adjusted to be thixotropic. The thinner layer enables drying more quickly. The body-compatible engobe recipe also means fewer issues with flaking during drying, better fire-fit.

The chemistry of the popular cone 6 Val's Turquoise glaze surprised a customer recently (when she was comparing the Gerstley Borate and Gillespie Borate versions). Here is what she said initially about using this on food surfaces:

"I’ve noticed the alumina is below the suggested limits. I have read that too low alumina can cause a glaze to be more prone to leaching, especially with the addition of copper carb. I’ve soaked samples in vinegar and lemon juice. I’ve also run pieces through the dishwasher several times with no visible changes."

Her concerns about this chemistry anomaly are valid. This glaze has no clay, that is very strange, clay sources vital Al2O3 that imparts durability. The little Al2O3 there is being sourced by lots of feldspar, that is a red light for crazing when little MgO is present (from talc or dolomite). Of course, even if this glaze does leach, the copper is not going to hurt anyone. However, if another heavy metal pigment were added the Cu could destabilize it enough to make toxicity a concern.

Her final comment was this: "I never want a customer coming back to me with a faulty pot. I just want to do everything within my power to make the best ware that I can - which includes a durable, reliable and functional glaze."

Top: Case molds (for pouring plaster into to make working molds) in the slicer about to be printed.
Bottom: Block molds (actually molds of block molds for pouring rubber into) about to be printed.
The top situation would have been a dream for a potter like me, the simplest possible way to introduce mold-making for slip casting into a process. However, my goal of print-and-pour was not met, this shape is not conducive to the extraction of the plaster without corner breaking. The block mold master (lower left) was made by pouring PMC-746 rubber into these molds. That works extremely well, there will be no problems making plaster molds with this. Notice how well it has preserved the printing artifacts, they look like wood grain. The white embeds enable inserting natches (that I make on the printer also).

These are pure Custer feldspar and Nepheline Syenite. The coverage is perfectly even on both. No drips. Yet no clay is present. The secret? Epsom salts. I slurried the two powders in water until the flow was like heavy cream. I added more water to thin and then started adding the Epsom salts (powdered). After only a pinch or two, they both gelled. Then I added more water and more Epsom salts until they thickened again and gelled even better. The result is a thixotropic slurry. They both applied beautifully to these porcelains. The gelled consistency prevented them from settling in seconds to a hard layer on the bucket bottom. Could you do this with pure silica? Yes! The lesson: If these will suspend by gelling with Epsom salts then any glaze will. You never need to tolerate settling or uneven coverage for single-layer dip-glazing again!

It is a clay, a very non-plastic one. These are fired SHAB test bars of Barnard Slip going from cone 04 (bottom) to cone 6 (top, where it is melting). Porosity is under 3% and the fired shrinkage above 15% from cone 1 upward (second from bottom). Drying shrinkage is 4% at 25% water (it is very non-plastic). The darkness of the fired color suggests higher MnO than our published chemistry shows (and also higher iron). The white areas on the lower temperature bars are soluble salts.

Since this is a fine particled material, it could likely be made plastic with a bentonite addition, likely 5% or more would be needed. Solubles could be precipitated using barium carbonate.

Shown here are Creality Slicer, Prusa Slicer and Simplify 3D. Each of these can import STL, OBJ and 3MF files. Each permits resizing, rotating, reflecting and duplicating individual items and can efficiently place and space multiple items and groups. Each saves or exports as 3MF files. On the right is the Fusion 360 print dialog where I can choose which slicer and which format to send.

OBJ files were introduced in 1980 for visual rendering (e.g. animation, gaming, special effects). Files store surface geometry as interconnected triangles and define surface textures, materials and colors. These features were overkill for early 3D printers.

STL (Stereolithography) files were developed in 1987 by 3D Systems specifically for CAD and 3D printing, having a single focus on geometry. They were simple and computationally efficient (and also unitless like OBJ, assuming mm). STLs permitted only one object. They dominated early 3D printing processes (FDM, SLA, SLS), where color or texture was irrelevant and provided a simple standard for industry growth. However, modern printers can now do color, texture and multi-material, thus...

3MF (3D Manufacturing Format) files were introduced in 2015 specifically for more advanced 3D printing. To OBJ they add object orientation, units, printing instructions and meta information. Objects in 3MF files can be manipulated separately in the slicer.

All three formats are generated by modern CAD software (for handoff to a slicer app). 3MF is the preferred one.