When beginning wheel throwers attempt to create sets of matching forms, using calipers and other devices to measure forms can often be difficult. In an effort to overcome this stumbling block, a technique successfully used by beginning handbuilders can be adapted by wheel throwers.
This technique involves using templates to repeatedly create an even, symmetrical form. In the coil-building exercise, you position the template next to the pot as coils are added, making certain the pot conforms to the profile of the template. The template is then used as a rib to scrape the excess clay as the form is rotated, creating a smooth, uniform surface.
Making a Template
Any number of objects can be employed to design templates that have a variety of shapes. French and ship curves, found in drafting or mechanical drawing sets, are excellent tools for creating profiles for wheel-thrown vessels. A variety of calipers can be taken apart to create any number curved forms. Lids of various sizes can be combined to create a mixture of curves (A). This process can also be used to produce templates with more complicated and compound profiles with relative ease.
To incorporate this technique into wheel throwing, I began testing various materials that might serve the function of a template. Sheet plastic, a durable material that can easily be cut and shaped, turned out to be the best material (B, C). Searching through scraps available at local glass-supply shops, I found 1/4-inch and 3/16-inch thick sheets that could be readily shaped into the desired profiles by cutting them with a power saw or handsaw. The edges can then be smoothed with fine sandpaper.
Creating the Form
To use a template, for a set of cups for example, prepare several balls of clay weighing between ¾–1 pound each. Throw a wide cylinder. Check the interior diameter, height, and width of the form with calipers. Tip: Make a template for the basic cylinder form as well as the finished piece. The first template, showing the width and shape of the ideal starting cylinder, can help you get the right basic shape.
Once you have your cylinder ready, wet the interior of the pot, but do not wet the outside. Avoiding excess water results in a stronger form that can better withstand manipulation and alteration when using the template. Position the bottom of the template so that it’s just touching the bottom of the pot and rests on the wheel head (1). The template should contact the wheel but should not be pressed against it. Hold the template at approximately a 45° angle, abutting the rotating clay, such that the clay moves away from the edge of the template (see 3). The template should not be held at a 90° angle to the pot as this may lead to inadvertently shifting the template into the movement of the clay.
The fingers of your interior hand slowly move up, pushing the clay out to the curve of the template (2). As the pot widens, the hand must move up along the interior of the form more slowly so that it remains symmetrical (3). After reaching the top, compare the profile of the pot and template. If the pot does not match the template, move the fingers of the interior hand down from the top to the bottom, pushing out where necessary, to conform to the profile of the template. This is often necessary for shapes with wider diameters. Refine the rim with a sponge or chamois and the cup is complete.
Large or Complex Forms
Templates are also useful in creating larger pots, particularly bottle shapes. This provides a method to quickly create multiples of the same form, but also the opportunity to explore changes to certain areas, such as the neck and rim. The process of working with larger forms follows the same steps as you would for cups, except the neck and rim are made without the template.
Make another cylindrical shaped pot, leaving the top portions of the wall, including the rim, thicker than the rest of the pot. Position the template (4) and push the clay out to conform to the shape, moving fingers on the interior up and down as necessary (5, 6). After creating the desired curve, pull up the upper portion of the wall to thin it out and narrow it in using a collaring movement. Note: It is very important to continue moving your hands up while collaring in to maintain a curve or arch in the shape of the wall. A wall that becomes too horizontal or flat may collapse. In order to collar in the pot, use the middle fingers and thumbs to constrict the neck. As you create the neck, pressing down on the rim with the first finger of the right hand helps to maintain a level top (7).
Use a flexible rib after each collaring process to refine the shape and maintain the desired curve (8). Using the rib also removes excess water and compresses the clay. After narrowing the diameter of the pot, the wall has been thickened (9) and can now be pulled up thinner. As the top becomes too narrow to insert a sponge to remove water from the interior, switch to using slurry to wet the clay instead (10). This allows your fingers and tools to continue shaping the clay without building up excess torque that might twist or tear the clay wall. Using slurry on the exterior, instead of water, provides a stronger clay wall.
Excerpted from Bill Schran’s “High Profile” article originally published in the May/June 2009 issue of Pottery Making Illustrated.