|Monthly Tech-Tip |
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.
I love making pottery, but I love the technical side more. I searched for all the test specimens in this 2020 load of cone 10 reduction ware first, then pushed it back in and forgot about it. For three months! I really anticipate the test results (I am developing and adjusting many of bodies and glazes at any given time). The data and pictures for them go into my account at insight-live.com, it enables me to compare the chemistry and physical properties of recipes and materials side-by-side. That teaches me which roads to abandon and which ones to pursue. My last kiln went back in for six weeks, so things are getting worse! If you are wondering, we use the C10RPL firing schedule.
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.
Are you a potter that depends on glazes made by others? Do you have your ware fired in someone else's kiln? Cannot mix clay body tests? Then the evolution of the quality and aesthetics of your work is being stunted. This mug is a good example of why. This is G3933, made by adding iron, rutile and tin to a 75:25 blend of our base matte and glossy glazes. It is crawling at a few sharp angles of the incised decoration, which means it needs a little CMC gum. I need to switch to an 80:20 blend for more matteness. Third, our red-burning body gives better color at cone 5, I need to test this glaze in the C5DHSC slow cool firing schedule. Finally, I would like the glaze a little darker so I will test increases in the rutile and iron. All of these changes are on my radar because I have my own test kiln and an account at insight-live.com to document them.
Ceramic materials are employed in the ceramic industry to make glazes, bodies, engobes and refractories. We study them at the mineral, chemical and physical levels.
Tony Hansen is the author of Digitalfire Insight, Digitalfire Reference Library and Insight-Live.com, he is a long-time potter, ceramic lab-technician and body and glaze developer.
The process of slurrying a clay body powder and dewatering it on a plastic slab or table.