These two unglazed pieces are made from the same clay, M340. They are fired at the same temperature. But the one on the right has 1% talc added. Greying of the color is a characteristic visual change as this clay body transitions into the vitreous state we target. That transition happens over a narrow temperature range. Because the raw materials naturally vary in the temperature at which they vitrify, we have to tune the recipe so that the transition happens from cone 5 to cone 6. It is accompanied by a drop in porosity of 2% or more (according to our SHAB test). Talc acts as a catalyst for this change; in this case, only 1% is needed. By itself, talc is refractory. Yet it acts as a flux here! The fact that it can effect this big of a change with only 1% is amazing. Interestingly, this phenomenon only occurs with tiny talc additions.

The mold on the right is PLA filament. Printed at 0.8mm thickness, it only weighs 38g yet is very strong. It removes easily from the plaster with a heat gun. The TPU flexible mold weighs 62g (the walls are 1.6mm thick) but it will need a PLA shell to hold the walls vertical (or far thicker walls). It took four attempts to print this. The surface quality is not nearly as good, especially on the top layers. Printing is much slower.

PLA is a bioplastic, made from renewables. It can potentially be composted. PLA is the most common type of filament used in FDM 3D printing. It has a low melting point, which eases printing and improves interlayer adhesion (but heat resistance of printed products is poor).

Regarding TPU, here is some advice from a follower (who uses a Prusa printer and gets better results than us): "The secret to printing with TPU is constant speed while printing. Under Print Settings, go to Speed. Set them all to 20 mm/s. Ironing will be greyed out unless you have it on. Then, in the next section, Dynamic Overhang Speed, set everything to 20 mm/s. Under Modifiers set First Layer Speed to 20 mm/s. Then under Auto Speed (Advanced), set Max Print Speed to 20 mm/s. This will prevent almost all webbing and other print issues. Some people also suggest reducing the Z-Axis Nozzle Retraction, but I have not found a need to do that."

Consider the advantages of making your own clay bodies using a propeller mixer and plaster table.
-Independence: You control product availability, quality and consistency.
-Flexibility: You control the recipe (with our help if needed). Fine-tune and adjust it over time to fit your needs and compensate for variations in material properties and supply.
-Special-purpose clay bodies are possible, ones that ceramic suppliers do not or cannot make.
-The slurry up process achieves better mixing and deairing than any pugmill. No aging needed.
-A mixer and plaster table are useful for so many other things in a pottery studio.
-Achieving the right stiffness is an integral part of the process.
-Recycling scrap, by slaking, fits the process.
-Local native clays: Slurries enable the use of a magnet to remove iron, a sieve to remove particulates and a settling process to remove soluble salts.
-Cleanup is easy so many kinds of clay can be made without cross contamination.
-It is rewarding - you will own the whole process, the bragging rights alone make it worthwhile for me!

This is version 10 of my Medalta ball pitcher case mold. I am still determined that a standard 3D printer with PLA filament brings complicated molds within reach of almost any potter or hobbyist willing to learn 3D design. The project has evolved to become hybrid, using both plaster and 3D prints in the final mold. Two views of the PLA prints needed to pour a plaster half-model are shown at the top.
-Plaster is poured into A.
-I attach threaded anchors to the underside of the baseplate C (using bolts through the small inner holes), they hold the plate firmly in place on the plaster half-model.
-B is a spacer, it is clamped to the underside of C (and aligned using bushings in the holes), it is only used during the model pour.
-Bottom: A is on a perfectly flat and level surface. It was filled with plaster just to the rim and then the baseplate was placed on top of it (the spacer acting to correctly position it). More plaster was added and a few minutes after this it was scraped off flush.
After hardening the spacer can be removed, the mold peeled off using a heat gun, and the plaster surface finished and soaped. The 3D render also shows one of the side rails, D. It holds in place by a flange that wraps under and locks into the holes (the last version used magnets; this approach has several advantages over that).

The 3D design of this handle mold was challenging because of the lack of a defining edge to guide cutting it, at leather hard stage, to accurately fit against the body of the bellied shape (a Medalta ball pitcher).
Center: I solved that problem by creating 2mm pipe along the path defined by the join between the handle and the spares.
Upper left: It has been 3D printed using PLA filament. The walls are only 0.8mm thick so printing is fast. The low profile means there is no bulging from the weight of the plaster. The clips and embeds are in place, ready for the plaster.
Lower left: The plaster cast mold halves (with natches and spacers glued into the embeds). I used a heat gun to remove the PLA prints cleanly (to preserve crisp corners).
Right: The halves fit together perfectly.

A kaolin shipment just came in. "UnReady Freddie" is panicking. He thinks he remembers that products made with the last shipment were lacking plasticity and the fired color was off. He is going to have to come up with different lame excuses for complaining customers this time.

"Ready Freddie" has Insight-Live and has collected years of data on incoming shipments in one searchable place. He knows what to check on each and has fired bars, in-mix tests, particle size checks, data sheets, lots of pictures, notes, etc. He also has traceability - he knows what material batch went into what product. He works with production to do material lot tracking and with purchasing to keep suppliers aware he is testing. Because Ready Freddie knows how materials vary he can compensate recipes and processes so customers see a consistent product.

UnReady Freddie has a few spreadsheets somewhere. But he is busy with other things. Who do you want in charge of product consistency (and company reputation)? Here is what to do next: Have your technician study the page "Testing a New Load of EP Kaolin" (link below). You will be hearing from him/her soon.

A user experienced this issue with five brands of gold luster, making them unusable. Panic ensued as looming orders could not be met. A session with ChatGPT finally provided the answer: Firing schedule. The preprogrammed fast-fire schedule in the electric kiln was too fast. It noted that organic compounds need time to burn out completely before 800°F. When kilns are densely packed, good ventilation is also important. Different vendors recommend different firing temperatures between cone 020-018. Unlike decal firings, the gold can, and even should, be fired while still wet.

Are you the technician at a company producing clay bodies, glazes, and underglazes? That creates a lot of data. Are you storing it in spreadsheets? That’s like filing lab reports in a shoebox! Searching for data ends up taking longer than the test itself. And it is seldom in the format you need, it is not linked to anything else, it doesn't have the information you need. Excel was not designed for this, your lab deserves a database. Databases enable insight. Insight-live.com is the right home for all the data you collect.

Imagine all your lab data in one searchable, structured, secure system — everything hierarchical, linked and accessible. Being able to compare results across time, batches, and processes. Having a full data trail. For example, maintain master recipes of everything and track their evolution — what changed, why it changed, and how it performed. Maintaining a file system full of thousands of spreadsheets is great for burying data.

The least expensive Shimpo banding wheel right now is $155. So I 3D printed my own as a test (this marvellous idea came from Crystal Bennett). The middle section is designed to fit inside the upper. To make it heavy, turn over the upper section, fill it to the brim with plaster, then press in the middle section until the plaster comes out of the holes (then weight it down till the plaster sets). The base is hollow, so it can be filled with plaster too. A standard 17x40x12mm roller bearing (available for $5 at the time of writing), it fits tightly into the recess in the middle section (and the base stem fits tightly inside of that). The resultant turntable turns super smoothly and rotates remarkably true. This drawing is parametric, so the dimensions can be adjusted easily. The size of the bearing that it will accommodate is also adjustable.

These glazes have not just crazed or shivered, they have pulled part of the body with them. What can generate forces great enough to create failures between glaze and body like this? Differential thermal expansion. Consider:
First, the glaze is thick. Very thick. Much too thick.
Second: A strong body:glaze interface zone has developed. That's good.
Third: The body is not firing to optimal strength (it appears porous). Not necessarily bad if the glaze fits.
What to do? Apply the glaze thinner, of course. But, testing should also be done to determine whether the glaze is under compression or tension. This could be done using the EBCT test.