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The Coil-and-Throwmaster

The combination of two techniques that came to be known as coil and throw has existed since ancient times. A method most often used when making large storage vessels such as granaries and oil containers – taking advantage of the gradual construction process of coil building and merging it with the uniformity of shape and surface produced by the pottery wheel.

Making pottery using coils had remained relatively unchanged until the early 17^th century when the Industrial Revolution when inventions such as extruders and pug mills completely changed the way ceramics were created. Until then, coils were made by hand-rolling them in a slow, labor intensive process. Extruders produce coils quickly, of uniform thickness and almost any length. Extruding coils from either a vertical piston type extruder or a pug mill has become the standard technique for coil made pottery.

When throwing a cylinder, the clay in the lower portion of the pot must have the standing strength to support the weight of all of the clay above it. Standing strength can vary with the clay type but the only way we can change the standing strength of the clay on the fly is by varying the moisture content of the clay.

Using the coil and throw method, we increase the standing strength of the walls of the pot by drying the clay as we build. Methods for accelerating the drying the clay such as blowtorches and electric heat guns are commonly used. These methods are fast and allow the drying to take place where it is most needed.

Potters are accustomed to adding water to the surface of the clay to create slip which lubricates the surface of the clay under the hands, minimising surface resistance.

Having dried the clay using heat, re-wetting the clay is to be avoided as this will weaken the the structure of the form. The surface of the clay must be kept relatively dry, requiring throwing techniques and tools that diminish the surface resistance.

Potters who train on the potter’s wheel are taught to aspire to clean, authoritative shapes with profiles that do not waver or hesitate. As the size of pots increase, this is much more difficult to achieve because in most cases the likelihood of weak form grows out of the techniques used to make large pots.

All plastic clays shrink as they dry. When new plastic clay is firmly joined to a partially dried clay, there is a shrinkage differential between them that must be resolved – if not with a crack, then the difference is usually resolved as a displeasing distortion of the profile at each join. This usually appears during the drying phase and is frequently appears worse after firing.

Variations in wall thickness guarantees distortions of the form and the role of the Throwmaster is twofold.

1. Your Throwmaster will come set with a gap of 6mm between the rollers. This ensures your pot has a constant wall thickness of 6mm from the bottom pot to the top.
2. The Throwmaster rolls the clay down to the correct thickness, avoiding surface resistance.

The Throwmaster makes it possible to minimise variations in shrinkage between each coil and achieve a smooth continuous profile in your pots, free of erratic and unsightly changes in the shape.

Who Is It For?

To successfully coil and throw it is necessary to have developed throwing skills to a moderate level. It is not for beginning potters.

Coil and throw should be within your grasp If you can throw a 150 mm high cylinder within 5 minutes.