Expand: date=February 2007

Construction

Picture frames have traditionally been made of wood, which is still the commonest and most prestigious material, although other materials are also used, including aluminum, plastics or polystyrene, even sea shells. A picture frame may be of any colour or texture, but gilding is common, especially on older frames. Some picture frames have elaborate mouldings which may relate to the subject matter. Complicated older frames are often made of moulded and gilded plaster over a plain wood base.

The picture frame may contain a pane of glass or a plastic glass substitute such as Plexiglas, in order to protect the picture. In some instances where the art in the frame is dispensable or durable, no protection may be necessary. Glass is common over watercolours, rare over oil paintings, except very valuable ones in some museums. Glass may be treated with coatings, the most common being UV filters. Some glazings such as Denglas, Optium, and Museum glass have a coating which makes the glass partially nonreflective and practically invisible under ideal lighting conditions. The elaborate decoration on this frame may well be applied plaster pieces stuck to the wood beneath For pieces to be framed under glass, except for the most disposable and inexpensive posters or temporary displays, the glass must be raised off the surface of the paper. This is done by means of matting, a lining of plastic "spacers", shadowboxing, stacking two mouldings with the glass in between, and various other methods. If the paper (or other media) were to touch the glass directly, any condensation inside the glass would absorb directly into the art, having no room to evaporate. This is harmful to almost any medium. It causes art sticking to the glass, mildew, and other ill effects. Raising the glass is also necessary when a piece is done in a loose media such as charcoal or pastel, to prevent smudging. Care should be taken with these works, however, if Plexiglas is used as a static charge can build up which will attract the pigment particles off the paper. Using real glass helps to prevent this.

Certain kinds of pieces do not usually need glass when framed, including paintings done in acrylic or oil paint (the former is usually waterproof; the latter actually needs to "breathe" due to the decades-long drying process), stained glass or tiles, and laminated posters. These kinds of pieces are still sometimes put under glass though if for example, they are framed using mats, or (in the case of oil paintings) they are kept in a carefully climate-controlled environment.

The frame along with its mounts should complement and project the artwork, art work framed incorrectly will not be shown to its full potential.

Styles

"L"-style frames are a simple variety that are constructed with a single L-shaped border of wood, with the bottom part of the L, or rabbet, at the front of the frame to hold in the glass, object and backing, which are secured in from the back.