Picture Frames: A Brief Introduction
A picture frame is a decorative edging for a picture, such as a painting or photograph, intended to enhance it and make it easier to display, or protect it.
Wood is the traditional material for making picture frames, and is still the most common material. Other materials used to make picture frames include silver, bronze, aluminum, metal, porcelain, Polyresin and plastics.
Picture frames are generally square or rectangular, though circular and oval frames are not uncommon. Frames in more unusual shapes are usually frames intended for photographs, such as heart-shaped frames to go around wedding pictures and the like. Also, differently shaped shadowboxes are made, though these have generally been used to roughly follow the outlines of sports jerseys or other memorabilia, rather than pictures. There are also picture frames designed to go around corners. Another popular design for a picture frame includes a scoop, an indent in the frame that adds depth.
A picture frame may be of any color or texture, but gilding is common, especially on older wooden frames. Some picture frames have elaborate molding, which is a strip of material with various profiles used to cover transitions between surfaces or for decoration. Complicated older frames are often made of molded and gilded plaster over a plain wood base. Picture frames come in a variety of profiles, but generally the lengths of molding feature a "lip" and rabbet, the function of which is to allow a space to hold in the materials in the frame. The lip extends usually about a quarter of an inch past the edge of the rabbet.
Picture Frame Glass
The picture frame may contain a pane of glass to physically protect the work of art from damaging factors such as humidity, heat, and soiling. Laminated glass and some acrylic may be used to protect against physical damage from glass breakage and to offer protection from a malicious attack. Regular glass, as well as some glass surface treatments can also filter some of the damaging ultra-violet radiation (UV) and heat (NIR).
Artworks that require protective glazing are those rendered on paper or fabrics (including photographs), which contain pigments and dyes that absorb UV and are susceptible to discoloration. Even if the framed object or artwork is UV resistant, UV protection can still serve the purpose of preserving the integrity and colors of non-conservation grade framing materials susceptible to UV damage, such as mat board.
Inside the frame there is usually a mat which is likely to be a thin, flat piece of paper-based material. It serves as additional decoration and performs other, more practical functions, such as separating the art from the glass. Putting mats in a frame is called matting, a term which can also be used interchangeably with mat.