Slurry Mixer, Propeller Mixer
An important tool in ceramics for mixing slurries. These come in lab sizes to huge industrial devices. Good mixers are absolutely invaluable in the studio and lab (for mixing glaze and clay slurries). Variable speed ones are very expensive (although they can be found on ebay.com).
Simple propeller mixer with mount and switch
This is a heavy- duty unit, a 1/3 hp mixer that can handle up to 10 gallons.
Optimimal casting slurry properties impossible without good mixing
A video of the kind of agitation you need from a power mixer to get the best deflocculated slurry properties. This is Plainsman Polar Ice mixing in a 5 gallon pail using my mixer. Although it has a specific gravity of 1.76, it is very fluid and yet casts really well. These properties are a product of, not just the recipe, but the mixer and its ability to put energy into the slurry.
A small laboratory variable speed propeller mixer
If you are at all serious about testing glazes and clay bodies, you need one of these. There are other methods, but nothing else comes close to this. These are expensive new, this one was more than $1000. But you can get them used on ebay.com. I adapted a mount (to give it vertical adjustment) from a hardware store. Propellers are also expensive, but you can design and 3D print them yourself or have them printed at a place like shapeways.com.
Testing your own native clays is easier that you might think
Some simple equipment is all you need. It is amazing how much you can learn from characterizing a body or clay material. You need a gram scale accurate to 0.01 grams (very inexpensive at your ceramic supplier). A set of callipers (again, not expensive these days). Some metal sieves (expensive, so search "Tyler Sieves" on Ebay.com). A stamp to identify samples. A plaster table or slab. A propeller mixer. And, of course, a test kiln. And you need a place to put, and learn from, all the measurement data you will be collecting. An account at insight-live.com is perfect.