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•The secret to know what to test is material and chemistry knowledge.
•The secret to learning from testing is documentation.
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•The place to get the knowledge is https://digitalfire.com

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Propeller Mixer

An important, even essential tool in ceramics for mixing slurries (body and glaze). Particles in ceramic powders can be exceptionally small (and often agglomerated) and wetting all their surfaces requires the injection of energy into a slurry that only a device such as this can do. This is especially important when the slurry is deflocculated and thus that a low water content. In addition, slurries get lumpy during use, you need one of these to smooth them back out.

Mixers can be purchased in lab sizes (e.g. with 1/20hp motor) to huge industrial devices. These machines must be treated with respect, they are potentially dangerous and can inflict serious injury if not used carefully.

It is important to have a good mounting system that enables leaving a mixer running for a period of time (minutes to hours). The mount should offer good control over vertical position and angle of the shaft and, if possible, RPM (adjustment of these parameters enables mixing without sucking air bubbles into the slurry).

Variable speed mixers are very expensive to buy (a small lab mixer can cost thousands of dollars). However they can be found much less expensive on ebay.com (ebay.ca in Canada) under the brand name "Lightnin". For mixing 3-5 gallon amounts you can make your own mixer inexpensively (about 1/3 hp motor is needed).

Simple propeller mixer with mount and switch

Simple propeller mixer with mount and switch

This is a heavy-duty unit, home made, with a 1/3 hp motor. It that can handle 5 gallons of high density suspension glaze or body slurry.

Optimimal casting slurry properties impossible without good mixing

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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 must-have: Laboratory variable speed propeller mixer

A must-have: 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. It is the most valuable and frequently used tool in any ceramic bodies and glazes testing lab. These are expensive new, this Lightnin 1/20 hp variable speed was more than $1000 many years ago! 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

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.

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By Tony Hansen

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