|Monthly Tech-Tip |
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 or classroom. These are expensive new, this Lightnin 1/20 hp variable speed cost more than $1000 many years ago, now it could be $4000! But you can get them used on ebay.com, it uses a 7.9mm dia (5/16") shaft. 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.
Some simple equipment is all you need. You can do practical tests to characterize a local clay in your own studio or workshop (e.g. our SHAB test, DFAC test, SIEV test, LDW test). You need a gram scale (preferably accurate to 0.01g) and a set of callipers (check Amazon.com). Some metal sieves (search "Tyler Sieves" on Ebay). A stamp to mark samples with code and specimen numbers. A plaster table or slab. A propeller mixer. And, of course, a test kiln. And you need a place to put all the measurement data collected and learn from it (e.g. an account at insight-live.com).
An example of how handy the ability to print in 3D can be. The worn-out stainless propeller costs $300 to replace. But the size and pitch of the blades is not right anyway. So I draw them using Fusion 360 and print them in PLA plastic, enabling experimenting with different sizes and pitches. While I could have one printed in stainless at shapeways.com I do not need to because these plastic ones are surprisingly durable. How about getting a tight fit on the shaft? No problem. I measured this shaft with a callipers and printed that size. It was a little tight so I printed slightly larger and it fits very tightly. One issue: If you mix slurries with hot water, it will travel up the shaft and the blades will bend.
This is my lab work area of mineral, frit, chemical, stain and metal oxide powders for mixing test glazes and clay bodies. Not shown is my propeller mixer, perhaps the most important piece of equipment we have. And my plaster table for dewatering clay body slurries. Building up something like this, over time, is practical for any serious potter, most of these powders are inexpensive. Within minutes I can plan and enter a recipe into my Insight-live.com account, give it a code number, print it and weight it out.
In ceramic studios, labs and classrooms, a good propeller mixer is essential for mixing glaze and body slurries.
Engobes are high-clay slurries that are applied to leather hard or dry ceramics. They fire opaque and are used for functional or decorative purposes. They are formulated to match the firing shrinkage and thermal expansion of the body.
In ceramics, the production of glazes and casting slips requires dispersing powders into water to create slurries. A good mixer is essential.
The process of slurrying a clay body powder and dewatering it on a plastic slab or table.
Understanding the Deflocculation Process in Slip Casting
Understanding the magic of deflocculation and how to measure specific gravity and viscosity, and how to interpret the results of these tests to adjust the slip, these are the key to controlling a casting process.