Monday, June 14, 2010

Building a Canvas

I just finished a building a large canvas for a commission. The next few posts will catalog the process of making one from scratch.

The main challenge I had in this project was finding suitable wood. The longest dimension was 50 inches, as specified by the client. When I build stretchers, I like to use well-seasoned older softwoods. Older wood was usually grown more slowly than the modern farmed variety. This makes it stronger and more dimensionally stable. Using it often involves reclaiming wood, sometimes reusing planks from old houses or furniture.

I wasn't able to find anything suitable at first in my collection, so I reluctantly went out and bought commercial lumber. Despite very carefully selecting the straightest pieces I could find, and letting them sit for several weeks, they started warping and bowing severely before I could even put the frame together. This was discouraging.

Luckily, I discovered a long plank of softwood, hiding in the rafters. This board was probably older than me, and well seasoned. Even after machining, only one board changed. I went ahead and ripped it into 1 x 2 size boards.

If a stretcher was made with regular 1 x 2 boards alone, the canvas would not wrap neatly around the inside edge. Commercial stretchers usually have a raised outer edge, rounded on the inside. This holds the canvas gently above the rest of the frame. Doing it this way myself would require complicated routing. An easy way to accomplish the same thing is to buy pieces of quarter-round molding and attach them to the edges of each frame bar. The one I like to use is not true quarter round, it is slightly wider on one side. The is called a base shoe.

The base shoe being glued in place. In woodworking. one can never have enough clamps!

The frame was built with mitered corners. Because of the size, several cross braces were added along with corner braces. Each bar used an alternate face, so if warping does occur, there may be some cancellation effect. It is not a good idea to rely on glue alone to hold a frame together, so all joints were reinforced with screws.

The finished stretcher lies in waiting on the canvas, cut to size.

In the final installment, I will stretch the canvas, size and prime it.

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