Creating straight lines on the outside of pottery can be a challenge. Creating those same straight lines on the interior of a bowl or serving dish can be a frustrating and time-consuming endeavor. In my work, I use cut vinyl laid out to create various patterns. Each piece of vinyl is placed individually, so guidelines are necessary to achieve even spacing. I use a tool made from a piece of wood along with a carpenter’s pencil to quickly and accurately draw straight lines on the inside of my serving dishes.
Using a ⅝-inch square dowel (found at local hardware stores) cut two pieces off the end that are the thickness of a carpenter’s pencil on the shortest side (about ¼ inch thick). The closer you are to the exact thickness, the more accurate the tool will end up being. With the remainder of the dowel, cut two equal pieces long enough to span the widest dimension of the work you plan to decorate. Glue the pieces together with wood glue, sandwiching the ¼-inch sections between the two lengths at opposite ends, creating a gap between the two long dowels (1).
Using the guide is straightforward. Place the guide over the lip of the pot, spanning where you desire the line. The carpenter’s pencil will fit nicely in the channel, allowing you to draw a straight line on the inside of the piece (2). I find that it’s best to use a pencil with a sharp tip; this ensures a clean and precise line (3). Move the pencil up or down following the form as you draw over curved interior surfaces to mark a continuous straight line.