Production Process » Clay Production
The process begins with an industrial clay mixer that I constructed mostly from scrap metals and surplus drive train components. The one pictured was completed in January of 2008 and produces 450 pound batches, which is double the capacity of my first mixer.
Producing clay on the premises allows for control of the raw materials that compose the clay body. This is a major advantage over purchasing commercially-mixed clays because they are generally intended for student use, as academic institutions are a much larger part of the market for the clay industry than studio potters. Pottery made from commercial clays rarely has the degree of thermal shock resistance needed to withstand years of oven use because the clay body was not formulated for that purpose.
Because durability was of primary concern from the start, i decided to engineer the clay body specifically for this product line, selecting only high-quality and consistent materials which are precisely blended to form an ideal clay body. I took a close look at a $5000 commercial
clay mixer designed for
studio potters and eventually built two of them - first one of similar capacity which i used for a few years and then sold to another potter; and then the much more heavy duty model shown here. The picture on the right shows the inside of the mixer
with blades that revolve at about 20 rpm and mix a batch of clay in about 20 minutes for about 1/2 the cost of pre-mixed clay.
The formula for this stoneware body evolved over the course of several years and is the result of extensive research and testing. The clay works well for wheel throwing and the pots can be moved quickly through the drying process with minimal cracks.
The picture on the left shows about 75 lbs of wet clay scraps dumped into the mixer, which is how I usually start the process of mixing clay. These scraps are reclaimed from the throwing and trimming process.
To this I will add another 300 lbs of dry materials, including four different types of clays and some feldspar to help the clay body fuse during the firing process and dissolve traces of silica, which is the main cause of oven ware failure if not dealt with properly.
Mixing clay this way solves the problem of what to do with the reclaim that accumulates quickly when doing a lot of production work. It is more efficient than drying the reclaim out on plaster slabs, a much slower method used by many potters that takes up valuable space. It also helps the newly mixed clay to age faster than it does when mixing entirely from dry materials.
To complete the mixing process, the clay is
run through a vacuum de-airing pugmill. This one was constructed from a section of 8" pipe and has an auger that revolves inside,
grinding and mixing the clay as it pushes it forward through a set of stainless steel screens that shred it like spaghetti. At that point it passes through
a vacuum chamber that removes virtually all the air from the clay before extruding it out the nozzle, ready to use. This greatly improves the workability of the clay and
eliminates the need to "wedge" the clay repeatedly, which is a strenuous and time consuming process that detracts from production work.
Next step: Glazing >>
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