Supports and Grounds
Wood Panels

Many varieties of wood have been employed, but the most common have been poplar, oak, linden, pine, and various hardwoods, such as mahogany and walnut. All wood has a cellular structure which enables it to absorb water. The cell walls absorb and discharge atmospheric moisture and swell or contract in the process. This continuous movement of the wood, which may show up as warpage or expansion or cracking, is, of course, a source of danger to the picture. The best protective measure the artist can take against the movement of the wooden support is a careful selection and preparation of a well-seasoned panel. Panels are produced either as plain-sawed or quarter-sawed lumber, depending on whether the log was cut radially or tangentially. The quarter-sawed wood is to be preferred since the grain on the front and back of the panel is more nearly the same. When the panel is prepared for painting, it should be given the same number of priming coats on front and back, so that the tension on both sides is equalized. Finally, a coat of oil paint should be applied to the back to correspond to the picture on the face of the panel and to protect the back of the panel from moisture. The attachment of restraining braces to the panel should be left to specialists in conservation of pictures, since the grid of braces, or cradle as it is called, must be expertly made and fitted and can do more harm than good if improperly constructed.

Wood may sometimes be attacked by fungi, which cause dry rot, or by certain insects, which eat and destroy wood. There are effective chemical treatments that can control these deteriorating agents.

The maximum width of a wood panel is usually determined by the width of the tree from which it was taken, but panels may be made by joining several boards together, edge to edge. Such joints, however, are always potential sources of trouble since they may separate or break open.

Well-seasoned panels may be made from sections of old furniture, but care should be taken to resurface the wood and to clean off all traces of the old finishing materials, such as varnishes and stains. [pp. 113-114]