Coil Pots Ideas

The Basics of Building Coil Pots

Even those who are new to clay should me able to make large and intriguing pottery using the coiling method. It is an extremely versatile technique and coil pots are capable of the greatest craftsmanship and artistry.

The clay used to build coil pots needs to be matched to the final form, meaning larger structures will need more strength. Their walls should be thicker, so choose a clay body for strength and also for a lower coefficient of expansion.

Clay bodies that have sand or grog in them tend to work best. Look for a shrinkage rate of 8% or lower. The clay should also be soft in consistency. Stiff clay won't weld together as well, which results in weaker joints that can crack apart. Clay should also be thoroughly wedged before you use it. This will homogenize it and remove air pockets which can cause blow outs in the kiln.

The floor or bottom of a coiled pot is usually a slab or patty of clay the same thickness the finished pot will be. The bottom slab should be substantially larger than the piece's diameter will be since it will be trimmed down later.

Once the slab is made, it should be placed on a support surface that will allow the piece to be moved safely. For a flat-bottomed pot, this support surface could be a bat or a disc of bisqued clay. For a pot with a curved bottom, a puki, a bowl-shaped mold made of plaster, wood, or bisqueware, is used.

If a puki isn't available, a regular bowl of the right size and slope can be used. However, it must be lined with several layers of newspaper or cloth before the clay slab is placed into it.

In sculptural terms, coiling is an additive process as the pot is created by adding material to it. Generally speaking, potters do use coils of clay, but additions can actually be made using other shapes, such as small patties.

Working the piece on a turn table, banding wheel, or kickwheel can make the coiling process much faster and easier.

Coiling begins on the upper surface of the pot's floor, not at the sides. Doing it this way results in a much stronger joint. Once the first coiled row is in place, the excess slab is trimmed off and the outer edge of the slab is welded upward into the coil.

Soft clay can be directly welded row-into-row. The strongest joints are welded on both the interior and exterior of the wall. Generally speaking, the thumb will be used on the inner surface moving downward, with the fingers on the outer surface welding upwards. If the clay has stiffened at all, score each surface to be joined, brush on slurry or slip, then lay the row and weld.

When coils are welded, the wall will thin and expand outward. The more aggressive the welding, the more the walls will thin and expand. Because of this, coils may need to be made substantially thicker than the final wall will be. As a general guideline, smaller pots will use coils 3/8 to 1 inch in diameter, and large pots will use coils 3/4 to 1-1/2 inch in diameter.

Coiled forms can take more time to create than we have available in one sitting. When you have to leave your work while it is in progress, place damp paper towels across the top row. Cover the entire piece with plastic.

If you want the bottom of the pot to stiffen slightly, leave some gaps where the plastic meets the table or shelf. Otherwise, tuck the plastic under the support surface. If the humidity is high, add a layer of newspaper or cloth in between the pot and the plastic. This will absorb any condensation, which could otherwise make your pot collapse.