FRAMING BASICS
Listed frame sizes are the size of the artwork which a frame can hold, without regard to molding width.
Frames are always made 1/8" oversized, thus a 16x20 frame actually has an opening 16-1/8" x 20-1/8."
Oil and acrylic paintings are normally framed without glass. Art on paper should be framed under glass, but ideally the artwork should not touch the glass.
Paper art can be sepa-rated from the glass either by window mats or by spacers (inserts in-stalled beneath the rabbet of the frame).
Some people are con-fused by the fact that they are charged for more feet of frame stock than the nominal size of the frame. It's easy to see why if you visualize a 1" square postage stamp framed in a 6" wide molding. More than four feet of molding would be required. Charged footage always reflects the amount of molding used plus a small allowance for the inevitable waste.
Wood was once almost the only material used in framing. Now a wide variety of synthetic materials has been added to the mix, plus a wide variety of aluminum frame styles. (Don't think that these look like the bumper from a 1957 Chevy. There's an almost endless variety of color choices.)
While not universally accepted, here are a few framing guidelines that are widely followed:
Mat width and width of the frame molding should not be the same. Usually the mat should be wider.No mat should be lighter than the lightest light in the artwork, or darker than the darkest. But note that many shows and some galleries mandate only white mats.Choose a cool frame color for art tending toward cool colors, and a warm frame color for warm art.For portraits, avoid a frame with a width equal to the width of the subject's head.