Left: 65% #6Tile kaolin and 35% nepheline syenite. Although it has great plasticity and fires white, it crazes the glaze and has 1% fired porosity (using the SHAB test).
Right: 65% M23 Old Hickory ball clay (similar to OM#4) and 35% nepheline syenite (feldspar would also work). The glaze fits, the body fires very dense (zero porosity) and plasticity is fantastic!
The body on the left needs a 20% silica addition (to stop the crazing) and more nepheline (to reduce porosity to porcelain levels). The remaining 40% kaolin will not be nearly enough for a workable plasticity (so bentonite will be needed). The body on the right does not need fixing; it works as is. Many feel that stoneware body recipes must be built on a feldspar-containing base clay having pottery plasticity (adding ball clay, kaolin, feldspar and silica and ending up with needlessly complicated recipes). But, ball clay is a base, all it needs is a non-plastic filler (to cut plasticity and therefore drying shrinkage) and a flux to vitrify it - feldspar or nepheline fills both roles.

Of course, this stoneware does not fire as white. But do you need white? Glazes will fire brightly colored on this surface. And, cleaner ball clays are available in many areas (even ball clays intended for casting will be plastic enough). It is also worth considering the use of a white engobe.

Until now, I have done these in Fusion 360. But in OnShape and my new dimensioning method they are even better. If you are a hobby maker like me, then OnShape is free. This updated design only has three parameters: ID (inside diameter), OD (outside diameter), and slack (addition or subtraction for a good fit).

Print all four of these at the same time. Repeat cycles of adjusting the slack parameter and printing again until they fit into and over each other well (the better quality your printer to smaller the "slack" dimension can be). Print them in multiples of seven: Two natches, two embeds, two clips and one spacer (these are the proportions in which you will be consuming them).

An advantage of OnShape is that it enables sharing; the link is below. To 3D-print it select all four, right-click on one of them, export to 3MF format, open that file in your slicer software, position (and replicate/orient items), then print or export to a G-Code file.

I am just a simple guy, a hobby 3D printing "Maker", I focus on making molds for ceramic slip casting. I don't need a "high maintenance" CAD partner.

Fusion 360 and I were not a good match. It was her world, Windows and Mac only - I had to live in it. She was the “Queen of Complicated”, always on the drama channel of new features far beyond what I needed, rather than refining the simple ones I did need. And she was expensive to take out, costing way more than what I needed ($750/year).

OnShape is my new chill. She will go out, at full power, to Linux and iPad. She's a keeper. I don’t need a user manual for her. She's not a princess but a partner, social not a snob. I don't feel like I am on a roller coaster without a seatbelt, rather I am with someone that is easy to be around and way more powerful than she looks.

This 3D-printed PLA pour spout potentially increases the utility of this one-piece plaster mold. As can be seen on the upper section analysis, the spout is designed to form the lip of this small Medalta Potteries bowl (and provide a guide for cutting its inside edge). It has lugs that extend outward to enable holding it down using rubber bands. I intend that it will be cleanly removable after the piece begins to pull away from the mold, leaving a high-quality lip that only needs a little trimming. This spout also permits precise monitoring of when to pour out the slip and it prevents most of the mess made using traditional molds having a spare.

This is the first piece I have made wholly using OnShape CAD. Experience with Fusion 360 gives me expectations of how this should work and those expectations are generally being met. Cost is no longer an obstacle to adopting professional 3D CAD for mold making. I am using OnShape on my 2014 Mac Mini running Ubuntu Linux (on 16gb RAM). And Prusa Slicer, OctoPrint, GIMP, Kdenlive, InkScape and productivity software are all running smoothly on it.

These (right) were made individually in the factory during the 1930s and 1940s (the insides have pronounced throwing rings and slip drips). The potters were able to make up to 500 per day, even though they took the time to smooth the outside using a rib! The inside base of this one is bowl-shaped (the walls near the base are very thick), this helps explain how they were able to throw them so quickly.

Perhaps most surprising is how much whiter and speck-free the bottle is even though it is fired four cones higher than the crock (Plainsman M340 at cone 6). Both pieces have porosities above 2%. Why? First, they got their clay from further east in Saskatchewan (near Willows), where the cleanest clays are much lower in iron contamination (likely the H0009 body). The whiteness is better even though they would have had to add some ball clay to make the clays more wheel-throwable. Second, they employed a wet process to refine the clay (slaking, blunging, sieving and filter pressing), this enabled them to sieve out the iron pyrite particles. Fortunately, modern dry grinding and air separation equipment is greener and able to accomplish without water.

Notice also the transparent G1129 glaze on the beer bottle (the upper section is likely the same glaze stained using iron oxide): After almost 100 years it has not crazed. This is both a testament to the ease of glaze fit these natural materials offer (because of the high quartz content) and the skill of the engineers of the time at matching the thermal expansion of glaze and body.

The original bottles were hand thrown and very heavy. This one, for example, weighs 525g. Our bigger slip cast equivalent with a modern shape, 3mm thick walls and much higher capacity weighs only 400g.

The color, enduring glaze fit and the type of clay used by Medalta indicates these were likely fired at least to cone 10. Energy was cheap at the time and the Saskatchewan clays they used require high firing.

This is a test mold to determine if the swing top stopper will work on a neck of this shape. This mold only weighs 87g and the walls are printed to only 0.8mm thickness. Two natches are sufficient to keep the halves aligned perfectly. Pieces will shrink about 12%, thus the larger size. We will use tissue transfers for the decorations, the GA6-B glaze for the inside and shoulder and G2926B transparent for the body.

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.

Because of the ease of 3D printing case molds at home I can now pour plaster in them also. Of course, I am not in production; this is about creating prototype molds. This technique makes it possible to be precise in the amount of plaster used, so there is almost no waste. My tools are simply a good propeller mixer, and a scale and a 3-D printer (and a cooperative wife). Here is my procedure:
-Counterbalance a plastic container.
-Fill the mold with water and pour into the plastic container to get the weight in grams (and thus cc's).
-Plug that weight into https://plaster.glazy.org, set it to use centimenters and get the USG recommended weights for plastic and water.
-Put that amount of water in the flexible plastic container and tare it.
-Dump in the plaster needed (no need to sprinkle it, I have a good mixer).
-Set the timer for 4 minutes and let it soak.
-Put it under the mixer (at an angle as shown), set the speed to create a whirlpool just shy of pulling in any air (thus avoiding adding bubbles). Mix for 4 minutes and then pour it into the molds.
-Clean the mixer blade and shaft in a container of water (and throw that away outside). Let the plaster harden in the plastic container (it breaks away cleanly later).
-Let it set overnight and use a heat gun and pliers to carefully remove the PLA from the plaster.