Have you ever wanted a slip mixer but haven’t been able to afford one? If you have the time and are able to find or purchase the right materials, you can try assembling your own.
Like many craftspeople, I filled a studio need by building a piece of equipment myself. Instead of buying a commercial slip mixer, I gathered parts and fabricated others to put together one of my own. Some pieces are better bought than made, including the stainless-steel shaft and two cast aluminum impellers that mount on the shaft, as well as the zero-tolerance bushing that mounts the shaft to the motor (all bought from Lehman Manufacturing, maker of the Slip-O-Matic series of mixers). Additionally, a few waterproof, sealed electrical switches are needed.
The electric motor was a lucky find at a motor repair shop. It has two speeds (a huge help when making slip), and it is ½ horsepower, capable of mixing about 300 pounds of dry slip.
I started with a 55-gallon trash can. I cut a piece of sealed MDF into a circle the same size as the top of the lid, screwed them together (with stainless-steel screws from the plastic side), then cut straight across about 1⁄3 of the circle (through wood and plastic lid). I reattached the pieces with a piano hinge (see 6).
Assembling the Mixer
The motor mount was made from 3⁄8-inch plywood, with a square for the motor to bolt to, three triangles for the square to rest against, and a rectangle for the base (1, 2). I tilted the motor about 15°—a good angle for proper mixing without generating too much of a vortex (and sucking air into the slip) (3). This was mounted to the wood lid, with rubber washers between the mount and the lid. Additionally, I added two triangular arms to the motor mount, meant to support the weight of the motor and stabilize the whole setup. I placed the motor about halfway between the center of the lid and the edge (see 6), making sure the assembled impellers wouldn’t be too close to the can walls (4).
By placing the motor against the mount, I marked where the shaft of the motor would need to pass through the lid, and cut that out with a hole saw used for mounting door knobs.
As for wiring, this is a good time to talk about safety. A slip mixer must have a waterproof, sealed switch (in my case, a switch capable of low speed, high speed, and off). Also, the mixer must have a switch to disconnect power to the motor as soon as the lid was opened either all the way (5) or even a crack. Without these, the user is at risk of serious injury. Anyone building a mixer (or any equipment) for themselves takes responsibility for their own safety, and that of anyone using the equipment. I will replace the trash can soon (6), as it seems to be fatiguing after 5 years of constant use, and I plan to upgrade to a rain barrel, as these are specifically made to hold liquids for extended durations.
This homemade mixer is reasonably inexpensive, and has the added advantage over a commercial mixer of two operating speeds. The low speed allows us to wake the slip up each day, without slurping air into the mix. The high speed is needed when mixing a full container from scraps and dry materials.
the author David Eichelberger is currently the ceramics fellow at Marlboro College in Marlboro, Vermont. To learn more, visit http://eichelbergerclay.com.