A picture frame may be of any color or texture, but gilding is common, especially on older wooden frames.
Picture framing glass may be treated with anti-reflective coatings to make the glass virtually invisible under certain lighting conditions.
When a picture frame is expected to be exposed to direct sunlight, or harsh lighting conditions such as fluorescent lights, UV filtering may be added to slow down the photocatalytic degradation of organic materials behind picture framing glass.
Frames in more unusual shapes such as football shapes, stars, hearts can be hand carved by a professional wood carver or carpenter.
There are also picture frames designed to go around corners.
Although framing borders in ancient art were used to divide scenes and ornamentation by ancient Egyptian and Greek artists in pottery and wallpaintings, the first carved wooden frames as we know them today appeared on small panel paintings in twelfth and thirteenth century Europe.
According to a historical series published in Picture Frame Magazine, these early "framed panel paintings were made from one piece.
The lip extends usually about a quarter of an inch past the edge of the rabbet.
The picture frame may contain a pane of picture framing glass or an acrylic glass substitute such as acrylite or plexiglas to protect the picture.
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. It causes art sticking to the glass, mildew or mold spore growth, 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.
Joan Miró once did a work specifically to frame with a flea market frame.