This is simple test can be done to determine if oversize particles are present in a raw material to be used for clay body manufacture. While materials are sold as minus 200 mesh, as you can see here, they don't even pass at 150 mesh. In each case, we have attempted to wash through 50 grams of the powder (using the technique of our WSR test).

All ceramic materials must be ground using particle size reduction equipment. This process enables removal of contaminants or reducing their size enough that they do not marr the fired surface of the body. This is a demanding task. Being able to measure it quickly enables spotting problems with a materials shipment (and therefore how well a supplier meets their quality obligations and the kind of product that can be made using it). Ball clays and kaolins are the most problematic, not just in particle size and contaminating particles but also fired color and plasticity.

Of course, a record of this needs to be kept. That is where your account at Insight-live.com comes in. Upload pictures like these or just make a note of the result.

3D print this, pour in plaster to make a slip casting mold! My previous work on this project assumed a smaller 3D printer (making it necessary to print flanged PLA mold sections that clip together). But larger 3D printers are now common, making the CAD work much easier. This drawing is parametric for height, body diameter, wall and plaster thickness, and neck height (for the full bottle set body=160mm, neck=96). This uses my standard clips and embeds (upper right). Neck vertices are proportional to height, so resizing works well. The top end is filleted to permit the longest possible mold on the print bed (diagonally). The bottom inside perimeter is chamfered, strengthening the default 0.8mm side wall junction to the base (that being said, be careful when removing it from the print bed, flexing too much will cause failure here).

Doing this smaller size is for prototyping and testing. Note that casting plaster on a 3D print creates artifacts (which will appear as wood grain, lower right), later I will create a hybrid plaster/PLA or rubber case mold. This PLA mold prints quickly, it has a hollow back side, permitting easy removal with a heat gun. There is no spare, it employs a pour spout, making the mold shorter and producing a better lip.

Need a stoneware slip casting recipe? L4768E or L4768H are a good choice. A glaze recipe? How about GA6-B (or similar)? Go full DIY with this, you will never turn back.

Glue one of these on top of your slip casting mold (using slip) and enjoy the many benefits. These are intended for people who make their own molds using the 3D printing techniques taught on this website. Among the advantages are the following:
-Less mess.
-Smaller, simpler molds (they don't need a spare).
-Overhung lips, more precise lips.
-Visible indication of casting progress.

Fatigue Freddie is scared he will to be the scapegoat if this load of incoming material if off-spec again. Production wants to start using it tomorrow. This stuff has not been consistent and customers have been unhappy. He doesn't know where to start. Management thinks there is no way to test all the runs they make so he knows this is the place to do it, when materials come in. But he's alone, there is no cooperation between production, sales, QC in feeding info into any kind of record-keeping system. His company doesn't take responsibility for product quality variations resulting from material variations.

Minimal testing: Give the shipment a new code in the recipe area of Insight-live. Enter what is known. Upload a picture of any certificates provided with it. Are all the pallets lot numbered? Record that in the notes. Are they all the same lot? Record that. Are the pallets sequentially numbered? Test one from each lot for oversize particles (very important for clays). Make an SHAB test bar also, get it/them dry (in the dehydrator) and into the kiln overnight.

This is the L3954B engobe. 15% Mason 6600 black body stain has been added (instead of the normal 10% Zircopax used for white). Of course, a cover glaze is needed for a functional surface. We put a lot of development work into producing a recipe fits this body, M340. It works even when thickly applied because it has the same fired maturity as the body. Lots of information is available on using L3954B (including mixing and adjustment instructions). Engobes are tricky to use, follow the links below to learn more. L3954B is designed to work on regular Plainsman M340 (this piece), M390 and Coffee Clay. Most important we document how to adjust its maturity, and thus firing shrinkage, to fine tune fit if needed. These bodies dry better than porcelains and are much less expensive, so coating them with an engobe to get a surface like this makes a lot of sense. Ed Phillipson discovered this 80 years ago, enabling selling ware made from these clays as white hotel ware.

These brass/plaster pyramids embed into plaster to provide a threaded hole that M3 bolts can screw into. That enables attaching 3D printed elements to plaster elements when making hybrid molds. Narrow inserts permit placement in cramped spaces and nearer edges.

These are made possible using M3 brass knurled nuts and M3 bolts that can be purchased on Amazon. The brass nuts can be pressed in using a soldering iron. The pyramid-shaped 3D-printed anchors are 13mm high, they will accommodate 12mm, or less, inserts (the longest ones in the kits shown here bottom left). The holes are 4.4mm dia at the top and taper inward at -2 degrees. Of course, you can adjust sizes and angles as needed for your application.

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).