|Monthly Tech-Tip |
Making a professional floor tile is about the back of the tile as well as the glazed surface. It is about a clay body that will fire strong and durable. One that is fine grained on which glazes will fire without pinhole and blister defects. About a non-plastic clay that will dust-press well and dry quickly with minimal shrinkage. And about a clay that vitrifies enough to develop the needed strength, yet not shrink so much that fired warping cannot be overcome. It is about a non-slip glaze. And, again, it is about being flat, very flat. A studio potter can actually make a flat tile, that is amazing. A small scale operation should be able to automate enough to make custom tile viable.
More information coming soon.
I rolled the clay over the tile and cut it to size using a fettling knife. The clay is vitreous, but it is not fine-particled enough to produce clean edges and corners. The reason for the raised edge on commercial tiles become clear on this first firing: The glaze can go right to the bottom edge without being in danger of coming into contact with the kiln shelf. Of course, because it was not cut using a cookie cutter, the edges and corners are not nearly as straight and perfect as they should be.
I pour plaster into this 3D-printed shell mold to create a working plaster test mold. Then I press and roll the clay into that plaster form. Then I lay stretch plastic wrap over the rolled surface. The subsequent cut (using the printed cookie cutter shown) rounds the edges perfectly as the plastic stretches downward into the cut.
Yes. The body is Plainsman M370 (~ 25 silica, 25 feldspar, 30 kaolin, 20 ball clay + talc to tune maturity), a plastic throwing clay with far too much drying shrinkage to be suitable for tile. It is 3.8 mm thick fired (vs. commercial tiles are 5-7mm) and 33cm (13 in) square. It dried absolutely flat between sheets of plasterboard. We have even achieved total flat drying at this size using Polar Ice. Bisque and glaze firing were on an alumina shelf in an electric pottery kiln (at 300F/hr up through quartz inversion on the glaze firing), a completely unsuitable method for firing tile evenly top and bottom. Cooling on both firings was free-fall in a fairly empty kiln. Yet, it is flat! And flexible enough that I could lay it on the cement floor and stand on it without it breaking! Of course, to produce these consistently, special furniture that sinks minimal heat and a kiln that can evenly apply it front and back are needed. This is doable for custom applications. Of course, to compete in the commercial market, they need to be dust-pressed and there are lots of specifications to meet.
Plainsman 3D, Mother Nature's Porcelain/Stoneware
|By Tony Hansen|
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