Fit? It has to stick well. And stay stuck during drying (and shrinking). And the bond has to survive shrinkage that happens during firing. This potter is doing thick applications of each slip (actually that makes them engobes). She uses stains, that's wise, metal oxides bring baggage when used to color slips (e.g. their decomposition can affect the bond, they can gel the slurry, flux the fired product thereby increasing the firing shrinkage of the slip). Stains are better because they affect slurry and fired properties less. But there are still enough issues that each colored slip deserves testing. This potter first slaked B-mix as a slip (it is highly plastic), using it at a runny yogurt consistency. But it bubbled when fired hotter than a cool cone 6. A switch to porcelain slip (which is non-plastic) is shown here. It flaked off as it dried (even in a damp box for 24 hours), also after bisquing to cone 08, and sometimes even after firing to cone 6. This signalled a drying mismatch between body and slip, the bond that managed to survive drying was weakened enough to fail on firing.

The solution was an engobe recipe that is super plastic and sticky. The popular Fish Sauce recipe is an example, it contains 10% bentonite and is unbelievably sticky. We formulated L3954B with this in mind. It adheres well to leather-hard clay and doesn't flake off (misfit is instead evident by surface cracking if its shrinks more than the body). And it is not highly vitreous, keeping its fired shrinkage low enough to match stoneware bodies. Mixing your own recipe also enables compensating the amount of feldspar if the stain affects the slip's degree of vitrification, and therefore fired shrinkage (e.g. blues, oranges, yellows).

3D print four of these and glue them together to make a large cookie cutter for producing slab-built mugs. 3D print the cup, fill it with plaster and remove the PLA using a heat gun. Roll out a thin slab of clay, press the cutter into it using a round wooden batt, make sure it is not sticking to the board and flip it over onto the plaster form. Handles can even be attached while it is on the form. If clay is plastic it can be used quite stiff. Experiment, adjust sizing and dimensions and reprint to fine-tune.

This has been drawn "parametrically" with OnShape. I only had to draw half of one of the quarters (I mirrored that, extruded and then did a circular pattern of 4). The downloads page (link above) has a free link to view this drawing at OnShape.com. To 3D print, right-click the part (from the list on the lower left, "Quarter 1" and "Cup"). Choose the Export option and select 3MF as the file type (it should go to your downloads folder). Open it with your slicer and print (turn the quarter over and make four). You can even export in formats that other CAD software can open. Better yet, import it into your OnShape account to see the design history and change multiple aspects of the geometry in the variables panel (the drawing will adjust automatically). Other dimensions (e.g. cut depth) can be edited manually. Parametric design is revolutionary and it is now accessible even to hobbyists; it fits my try-it, adjust-it and try-it-again way of working.

These are made by Barbara Childs Pottery (I saw them on sale in a tourist shop in Alaska). To keep costs down, I first assumed they use dipping glazes they mix themselves. Potter's Choice PC-32 Albany Slip Brown and PC-20 Rutile Blue hobby glazes emulate these long time pottery glaze recipes. However, a reader noted that Barabara Childs uses Clay Art Center’s Stellar Rust and Floating Blue (with guest appearances by Blue Green). But Amaco and Clay Art don't just use the traditional recipes; they adapt and improve them. Consider the rutile blue. Neither is using the traditional G2826R floating blue recipe, there are new and better ways using recipes like GA6-C and GR6-M. Likewise, with the brown, they are not using the traditional G2415E Albany Brown recipe. Rather, they improve it (e.g. like we did with G3933G1). High on their list of improvements would have been a way to reduce or remove the lithium to cut costs. Maybe you are a hobbyist and don’t feel you need to DIY your costs down. But do your customers feel the same way? Not buying just ten small jars of hobby brushing glaze will pay for a mixer and much of the ingredients to make gallons of each of these as dipping glazes. It will also set you on the road to gradually improving the glazes you use. And even reducing your prices. What about buying premixed powders? Yes, that is much less expensive. But if you are mixing the glaze from one manufacturer with the clay body from another, crazing is an ever-present issue. Mixing your own enables an adjustment to fix the problem.

Why did this happen? There is a perfect storm of factors. Draining, during slip casting, creates suction and slip is heavy (1.8 times heavier than water). And this mold is tall with a narrow neck. So that creates a lot of suction. A slip having inadequate fluidity complicates draining. This round shape, even with printing artifacts, also releases well. How can this issue be avoided?

-Draining the mold carefully, holding it near horizontal for much of the drain.
-Use a well-deflocculated slip.
-Add bentonite to the slip, perhaps 0.5%, to make it stickier and slow down release time (which also slows down the casting time).
-At times, this will happen despite all efforts. In that case, if might be necessary to use a tube (e.g. 1/2 or 5/16”) to pump most of the liquid slip out of the bottle before inverting it. Adapt a 3D printed pour spout to keep the tube centered, at least near the mouth of the bottle.

It is very hard to let Fusion 360 CAD go. But the approaching $750 renewal is powerful motivation! OnShape is amazing. There is nothing to install, it runs in a browser tab like Google docs (see picture below). Sure, it won’t run offline, but I am almost never offline. It functions very similar to Fusion 360 for my basic requirements of making molds for slip casting. Recent experience with the complexity and slowness of Solidworks for Makers, which is total overkill for what I need, really makes OnShape look good.

My OnShape drawings are stored in my cloud account and are public. That sounded bad at first, but it also means that they are shareable with others (another person, whom I choose, can actually work on a drawing at the same time as me). The full OnShape is working in Firefox on my 2014 Mac Mini Ubuntu Linux machine. This is beyond exciting to me, traditional CAD has always required expensive hardware that is far beyond a hobbyist (of course, OnShape will also work in Safari on Mac and Chrome on Windows). A real bonus: I can edit drawings on iPad in what appears to be full power mode (although a mouse and keyboard are needed for serious work).

Besides the above, here are some of the features and advantages I am seeing:
-It opens and saves many professional CAD file types (a major drawback in SolidWorks for Makers).
-It is really fast, login is quick and a drawing can be open in seconds, this is way better than xDesign for Makers (from Solidworks).
-Documents are always saved, close one by simply clicking the home icon on the upper left.
-The timeline (called the "Feature Tree") can be reordered, turned back and has folders like Fusion 360.
-To 3D print just select part of your drawing, right-click and choose to export it in 3MF or STL format (it goes into the downloads folder).
-All tools are in one long, monochrome ribbon of tiny icons at the top but there is a tool searcher.
-Like Fusion 360, sketching constraints are inferred as sketches are created and applying them works in a similar fashion. Their tiny symbols display in groups and associate to the point or line by a light grey line. Automatically applied constraints can make sketches behave in strange ways until you learn to find and remove the offending ones.
-Constraints and dimensions are movable so drawings can be uncluttered for printing.
-Section analysis is in the "Camera and Render Options" pop-up under the view cube.
-The spline and bezier sketching tools are not as interactive (a downside of running in a browser).
-Parameters, called variables, are more in your face; they are even shown in the timeline.
-Panning, rotating and the viewcube work a little differently. The iPad version of OnShape beats Fusion easily in this respect.
-OnShape does appear to support text along a path like Fusion.

The secret weapon of learning OnShape: An AI chatbot. Just ask any question about how to do something. One helpful migration from Fusion 360 is to print the sketch(es) (with constraints and dimensions) and work from that to create the equivalent in OnShape. An advantage of OnShape is that if you get stuck (e.g. drawing goes red), you can share a link with a more knowledgeable friend to tell you what is wrong. Most often the issue is conflicting constrains.

The original bottles were hand-thrown and very thick and heavy. These are perfect candidates for slip casting.

Drawing and 3D printing a case mold became my first success using OnShape. CAD is difficult, I really needed a tutorial that explained OnShape in terms of Fusion 360 I already knew. There wasn’t one! Now there is. This new procedure I have developed supersedes all of what I have done so far with beer bottle molds.

This is a test mold. This mold weighs 87g and the walls are printed to only 0.8mm thickness. We just pour in the plaster and remove this PLA print using a heat gun. Two natches are sufficient to keep the halves aligned perfectly. Pieces will shrink about 12%, thus this larger size. We will use a cone 6 casting body, tissue transfers for the decorations, the GA6-B glaze for the inside and shoulder and G2926B transparent for the body.

Management now thinks they can outsource his technical work. Danny was good, but he didn’t build a centralized, searchable record of material testing, shipment histories, specs, production problems, and solutions. Instead, his knowledge is buried in thousands of Excel and Word docs and PDFs. He should have used Insight-Live.com to organize, interlink, and preserve this critical data. Sadly, the company does not even realize what they face without Danny:

• Slower problem-solving and loss of institutional memory.
• Greater dependency on outsiders who lack long-term investment.
• Inability to verify product claims.
• Quality drift leading to recalls, rework, and higher warranty costs.
• Innovation slowdown.
• Eroding customer trust and ballooning consultant costs.

Had Danny been not just a watchdog but a technical innovator, suppliers and consultants would have been secured to support—not replace—his in-house expertise.

Management says AI can do most of the technical work now. Tommy had no automation, no models, no data pipelines. Just “the way we’ve always done it,” trapped in spreadsheets and sticky notes. When the new AI system went live, his expertise didn’t plug in. It got left behind!

• The AI could really have used his seasoned human oversight.
• Years of hard-won knowledge lost in a digital junk drawer.
• Outside consultants are charging a premium to relearn what he already knew.
• Errors slip through because no one taught the machines better.
• Innovation stalls while the company rebuilds what he could have bridged.

Technicians aren’t just there to keep things running—they should teach the future how to work. Refusing to adapt doesn’t protect your job. It writes your own pink slip.

This potter almost has the casting process working, making these beautiful porcelain mugs. They are fired at cone 6 using a transparent glaze over underglaze decoration. But the devil is in the details. Look closer to see it: Crazing. Why? The reason is evident on the SDS for the body. Notice it has 10.5-15.8% crystalline quartz (or silica). This is not enough to prevent crazing in typical glazes.

Almost always, the solution is to find or formulate a clear glaze having a lower thermal expansion (in this case, a lot lower). But with casting bodies, we have another option: Mix our own. Unlike glazes, porcelain recipes are typically just three materials: kaolin, feldspar and silica. The starting percentages are simple for cone 6: 30% feldspar to vitrify. And 25% silica to fit the glaze. That leaves 45% kaolin. It is that easy! Start with the L3778G recipe. Its information page is also a launching pad for dozens of links, enabling you to dig as deep as desired into understanding casting slips (the materials are cheap, so losing a few batches while you learn deflocculation is not a problem). Still think it is too difficult to mix our own? Consider that you need a propeller mixer anyway to prepare and adjust the slip and reprocess scrap. By mixing your own you'll be a more effective, and flexible slip caster.

This plate, by Pablo Picasso, is on display in the art gallery on our Princess cruise ship. While others notice the underglaze designs, and the $40,000 price, I notice the absolutely crystal clear and bubble free transparent over glaze. How did he do that? At the Madoura studio they used leaded glaze, so Picasso himself doesn’t get the full credit. By his time, European low-fire traditions already had a well-matched clay/glaze system based. Glazes were made from mostly lead bisilicate frit with enough kaolin or ball clay to suspend the slurry. The lead melted so well that significant silica could be tolerated (20–30%) to reduce the COE. They didn’t use talc in the body, rather it would have contained 50-70% ball clay/kaolin, some feldspar as a filler (since it does not flux at low fire) and enough quartz to raise the thermal expansion within the range of the glaze.

Most potters struggling with borosilicate glazes would envy what leaded transparents can do. Any hope of even approaching them using boron glazes lies in keeping temperatures at or below cone 06, a thin glaze application, a low carbon body and ceramic stains rather than metal oxide colors.