A coil resting on your work board often holds clues about whether or not it’s even before you build anything with it. If it’s thicker in the middle, thinner at the ends, cracked on one side, or flat on the bottom, the wall you build with it will likely be flawed in the same way. Rolling coils seems easy, but it takes some skill, a steady hand and just the right clay consistency.
In general, coil rolling for hand-building doesn’t need to produce perfectly round clay rolls but they do need to be evenly thick. If a portion of the coil is much thicker than the rest it will add weight to that section and you will see a thickened area in the wall. If a portion is too thin it is more likely to crack while you’re trying to bend it or press it into place and when coils of varying thicknesses are stacked into a form you’ll end up with an awkward leaning structure. You’ll need to do more smoothing to clean up the joints, which can be problematic if you are building with thin walls.
Begin rolling the coils from a small piece of clay rather than a big piece and roll the piece loosely into a small cylinder between your hands, placing it on the work board. Then, start at one end and roll the clay in a back and forth motion using both hands moving from the center outwards. The pressure must be consistent over the entire length of the coil. If you press harder on the ends you’ll end up with a tapered coil or if one hand presses harder than the other the coil will become twisted or flat on the bottom.
Pay close attention to the surface you’re rolling on since you may need to make small adjustments to keep things even. If the surface is too moist your clay may just slip around rather than roll out. A dry surface will dry out the coil which will cause it to crack. If your clay begins sticking to the work board, resist the urge to add more moisture since this will just make the coil soggy and weak. Carefully pick up the coil and flip it over to see whether the clay itself is wetter or drier than usual or whether the surface you’re rolling it onto needs a little attention.
Pay attention to how you’re using your hands and fingers since flat hands tend to roll the clay more evenly than fingers alone. Fingertips create grooves in the soft clay while flat hands tend to press it out evenly. Keep your hands relaxed as you roll the clay with even pressure in a back and forth motion, which will feel like a light guiding or pressing rather than a heavy crushing. As the coil gets longer you can extend your hands gradually from the middle but be sure not to pull on either end since this will only stretch the clay thin.
A worthwhile exercise to practice is rolling out several small coils with the same clay body and observing what each roll will need or how you may need to adjust. Try rolling out a coil quickly, a coil with light pressure, a coil with heavy pressure, and a coil with a slow rolling back and forth motion from center to outer edges. Note how long each roll took and how long the coil is, then examine each coil from the side and underneath. Gently bend each coil and note which cracks, which flattens, which tapers, which twists, and which rolls out with consistent evenness. Observing the coils this way will teach your hands more quickly than working with several thick clay walls right away.
When you feel a coil is ready, it should bend with little effort and not leave a thick bulge when you press it against the surface of the form or another coil. Before adding a coil check whether the form and the coil are at the same level of moisture since joining a very dry surface to a wetter one often causes cracking later. Score and slip the areas where you expect to add the coil only, and press the coil gently against the scored area without pressing too hard and deforming the coil. Check the seam on the form to see what needs attention since you may need some extra blending, but remember you can easily blend a coil while it is soft and before it dries out.
Practicing rolling coils is more helpful when you begin to observe what the coil is doing and not just focusing on whether the coil will join to the form you have built. Try to notice if the clay is rolling or slipping as you roll it out, if it is cracking as you roll, if the ends are thinning out, if it’s staying thick in the middle, if it is flat or twisted on the bottom. Making small observations about the coil will help guide the rolling process rather than discovering you made a bad coil when you are already ready to join. Having a consistent coil is the easiest way to create a good wall.