I’ve reached a point in my life where everyone I know, myself included, is taking a ceramics class on weekends. I’ve started to notice every instance of ceramic material, and how prevalent it is around me. This trend extends into my professional circles too – many of my academic colleagues and peers are also interested in ceramics. I work in a very specific corner of academia, somewhere between human-computer interaction, craft work, and philosophy, doing things like using a giant embroidery machine to create conductive textile circuits and soft speakers. The lab I work at now recently acquired a Wasp 2040 3D printer, which is huge, and can print clay. I have students come in all the time asking about running experiments, like using mycelium clay in the printer, or creating parametric pottery, and I'm excited to explore the possibilities with them.
The most clicked link from last week's issue (~17% of opens) was a video of bicycle tire manufacturing in Taiwan. Tomorrow on the Members' Slack, we're hosting an AMA with the multidisciplinary designer and engineer Andrew Edman, a mild-mannered medical device inventor by day and a speculative product designer by night.
PLANNING & STRATEGY.
There are a lot of challenges to clay printing. For one, clay has to be moist enough to squeeze through the extruder and bond to the previous layer, but also hard enough to not fall over. Clay is also pretty heavy and doesn’t harden immediately after being printed like traditional 3D printers, so the thickness of each layer, speed of the print head, and corner radius of each layer is critical. The parameters of making a reliable clay print can be divided into 3 categories: rig, print head, and clay delivery. By rig, I mean the software driving the printing process, clay delivery is how the clay gets to the extruder, and the printhead is the mechanism that deposits the clay onto the print bed.
There has been a wide variety of experiments on similar types of printers that extrude pastes, each with its unique challenges depending on the material. My favorite example of this genre is the classic PancakeBot printer, which only prints one layer of a very viscous material (pancake batter), but relies on timing to create patterns in the batter as it cooks. Other food printers have successfully created multi-layer food prints like this robot arm that creates customized snacks, or this vegan 3D printed meat replacement. One of the most successful is the Cocoa Press, which creates beautiful 3D fully chocolate sculptures by making sure the entire print supply of chocolate is preheated before printing begins, then the chocolate cools rapidly once it's been extruded. I think these food printers are interesting because they offer a new degree of customizability for food, like ensuring your snack has a specific nutritional composition. This toothpaste printer, while somewhat silly, can print sticky substances by avoiding sharp curves and creating distance between the extruder and printed material.
MAKING & MANUFACTURING.
Traditional 3D printers rely on the properties of thermoplastics to build strength in the final print. The plastic starts as a rigid and spooled filament, which is pushed through a gear mechanism, and then melted immediately before being squeezed through an extruder and delivered to the print bed. This method is called a direct drive extruder, and is most common in older 3D printers. These are also really handy if you’re using a flexible filament. The other popular method is a Bowden extruder, where the filament is mounted to the frame and pushed through a PTFE tube to get to the extruder. There's a huge debate on the pros and cons of each method, but neither of these would work for any kind of paste or clay printer.
There are two main ways to deliver clay to your print head: A ram/syringe style, which pushes the clay mechanically through the extruder, like this DIY air-dry clay extruder used here to make clay trinkets. You can also use air pressure, but it requires a bit more of a setup. The Wasp printer uses a print head that has a screw extruder, which allows for more control over the flow and consistency of the material. Fun fact, pasta extruders also use a screw extruder.
MAINTENANCE, REPAIR & OPERATIONS.
While throwing clay on a wheel, it is easy to accidentally destroy a piece by having it collapse. By the end of every session, you’ll always have a ton of scrap pieces and a pile of watery clay, called slip. After working with clay on a wheel for a while, it may start to lose its plasticity and won’t behave the way it did when it was fresh – it might flop over or be difficult to work with. I find it remarkable how many times clay can be reworked and reclaimed into fresh clay by being dried out or moistened, and it can regain its original properties seemingly endlessly.
But once your clay has been fired, it changes quite a bit, it becomes rigid and fragile, and it can’t be reclaimed. In contrast to the malleability of wet clay, fired clay can be difficult to repair. One common method for repairing porcelain is a Japanese technique called kintsugi, which uses gold powder and lacquer. This process can take months to fully dry and is only food safe so far as you never heat it and are careful when washing it. The only other method for repairing porcelain is using a food-safe epoxy.
DISTRIBUTION & LOGISTICS.
G-code was invented at the MIT Servomechanisms lab in the 1950s, and is the most common way to control CNC machines, including 3D clay printers. G-code doesn’t use any logic, instead it uses a series of commands to control a tool and any associated mechanisms – like heat, bed position, and leveling. Parameters such as wall thickness, infill, and how fast or slow the machine lays down the material need to be finely tuned or your print will fall over! One particularly tricky thing about printing with clay is that you can’t print with supports. Unlike plastic supports, clay won’t snap or peel away once your print is done.
There have been a ton of unique fabrication machines that use bespoke G-code, like this solar-powered sand melting machine, or this CNC-like sequin flipping clock. Tools for designing files that are suitable for fabrication is also an area where clay printers are beginning to emerge as well, like GCODE.clay and this spiral cup project. I’ve seen similar crafting/code tools like AdaCAD, which is an open source software that allows you to create parametric weaving designs, and hope to see something more.
INSPECTION, TESTING & ANALYSIS.
Glaze is the smooth, glassy coating that covers most ceramics, which are porous underneath. While every glaze is different, and ceramicists often concoct custom mixtures of their own, they are primarily composed of 4 elements: glass formers, refractory materials, flux, and colorants. The glass former, which is often made of silica, quartz, or flint, is responsible for coating and sealing the piece. Silicea, the most common glass former, has a melting point of 1710 c, which is hotter than any kiln and must be used in combination with fluxes that lower the melting temperature. Refractory materials such as alumina help to stop the glaze from falling off the clay as it liquefies and melts. Finally, various metal oxides can be used to create unique colors and effects.
Glazing is really about chemistry and there are a plethora of toxic chemicals that are still commonly used in the process such as barium, selenium, or cobalt. These are used in small amounts, and by the time the glaze has been fired and cooled, the compounds aren’t harmful to the end user. However, lead and cadmium glazes were used as a flux component in glazes until 1971, and unlike other glazes, many leave residual traces of lead on the surface even after they are fired. Lead creates a clear and smooth coating letting bright colors shine through which is why it was so popular, and cadmium is used to create bright orange and red colors.
Uranium, thorium, and potassium were also commonly used and unexpectedly resulted in radioactive glazes to make vivid colors, including famously in this Fiesta Cookware set. If you own this dish set, don’t worry, there's no evidence to suggest it's ever caused anyone any harm! Not all glazes require so many ingredients. Some of the first glazes were invented in China around 1500 BC and just used ash, which naturally contains all of the components needed. Firing large amounts of wood and collecting the remains was a common technique to make a glaze. Some variants used straw, rice, or different types of wood to create variations in glaze colors and textures.
SCOPE CREEP.
- Clement Zheng's ceramic circuits that control sound with your food.
- This lab-grown salmon is another approach to fabricated food, and my favorite lab creation is the Cosmic Crisp apple.
- All Yarns Are Beautiful is a hack for controlling Brother knitting machines with your computer. I really love this technique of embedding materials inside a clay 3D print as it is happening.
Thanks as always to Scope of Work’s Members and Supporters for making this newsletter possible. Thanks also to the Sketching In Hardware community for inspiring me!
Love, lee
p.s. - I’m just starting my journey with 3D printed clay, let me know if you have any suggestions!
p.p.s. - We care about inclusivity. Here’s what we’re doing about it.
