Slab Construction Technique Using Internal Support
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This is a versatile technique I use to make relatively large pieces that are hollow and light-weight. Slabs of clay are wrapped around fabric “pillows” filled with vermiculite. The vermiculite provides support while I work on the piece. When the clay air dries to become leatherhard, I cut the piece open and remove the pillow. This is an alternate technique for coiling.
Making the Pillows
|Choose a fabric for pillows that is thin and light weight yet durable. Cotton sheeting is ok, but synthetics work best. You want a material that will not absorb much moisture. A tight weave is also important to hold in the vermiculite and fine particles. Making the pillow involves simple sewing skills. I make a pattern of the basic shape I want for the sculpture. For example with a head piece, I make a cylinder pillow which consists of a side and a circular bottom. Make the length of the side 3-4” longer than the length you want for the piece so you can close the top after you add the vermiculite. Sew the two pieces together. Here are examples of pillows I’ve made (1) and the corresponding shape I want to make. You want to keep it simple. The pillow needs to be a little smaller than the piece you intend to make.|
Filling Pillow with Vermiculite
Vermiculite is a light weight material made by heating mica until it expands. Most people are familiar with it as an ingredient of potting soils. There are several advantages to using vermiculite to fill pillows. It is light weight and easy to handle. It can also pack down, so as the clay dries, it can be compressed to a degree and therefore not cause the clay to crack. Because it has already been fired, there is not a problem with fumes in the kiln or unfavorable reactions with the clay. There are several sources for vermiculite. Most gardening supply stores carry it in small bags. Since I use a lot of vermiculite, I buy large 19 lb bags marketed as Concrete Pool Base Aggregate from a local building supply. It is more economical than horticultural grade vermiculite.
!!! Safety note !!! Vermiculite can be very dusty and I wear a pollen mask whenever I fill pillows. Get in the habit of wearing pollen masks in any dusty environment. ALL dust is bad for your lungs. Always take care of your most valuable equipment-your body! You got it for free, but it is nearly impossible to get replacement parts for this amazing, versatile tool.
Making the Initial Cylinder
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|Because I make so many pieces, I use a slab roller ,but of course, hand formed slabs can be used. I make ¼ to ½” thick slabs. Place the cylinder pillow on the slab and determine the size you want and cut accordingly. (2) There should be about a 1” side overlap. Roll the pillow into the slab until there is just a few inches of overlap left. (3) Place a line of slip on the farthest edge of the slab. (4) With the nozzle end of the cylinder facing toward what will be the top of the sculpture, roll the pillow away from you, pulling the closest edge of the slab around the pillow. When the two ends meet, roll the entire form until the seam line is on top. Knit the ends together. (5)|
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