Support problems. Over the centuries, artists have painted on a great variety of materials. In the parlance of conservation, these materials are called "supports." The most common supports are fabric ("canvas"), wood ("panel"), paper and cardboard, and glass. Each has its own advantages and disadvantages. Most are extremely vulnerable to high levels of ambient humidity, quickly becoming warped or wavy and vulnerable to attack by mold, mildew, and fungus. Canvas and paper products become brittle with age and are easily torn. Glass is easily broken and does not bond well with paint. Conservation treatment often includes steps to eliminate or mitigate these problems, with the goal of stabilizing the artwork and/or making it more presentable.

About the photos. The photos at right illustrate planar problems frequently encountered with oil-on-canvas paintings. During shipping,a blunt object crushed the side of the top painting's crate, pushing the center of the canvas inward and causing the brittle tacking edges to pop loose from the stretcher along the top and left edges. The other painting, by contrast, developed most of its planar problems as a result of internal forces; the "quilting" was caused by cracking and cupping of the paint, while the ripples in the canvas are attributable to a poor quality stretcher and poor mounting of the canvas on the stretcher. The dent at left center was caused by pressure from a blunt object during transport or storage. In this case, the painting did not break loose from the stretcher. After treatment, it is dramatically more planar.

Whittrege landscape coming off of stretcher & serious planar distortionsplanar2 landscape before treatment: Dent, ripples & quiltingplanar2 landscape after treatment: Planar