Framing a painted canvas with a colored mat is not only a great way to complement the artwork, but to preserve the artwork for years to come. Use a mat made from acid-free materials and labeled as "archival." Mats prevent the artwork from pressing against the glass, and thus protect the painting from moisture damage. Mats improve the value of a painting and are easily obtained at your local frame shop or hobby store.
Things You'll Need
Measure your painting with a tape measure. Record the length, width and depth.
Turn the frame over and measure the inner lip for width and length. This measurement will be the outside width and length of your mat.
Determine how much of your painting you would like to show, and measure the inside cut of the mat accordingly. Balance your choice of mat width by considering the style of the frame and the size of the painting.
Order your mat from a frame shop or a hobby store, since special tools are required to cut the mat.
Place your mat behind the glass and lay the painting behind it. Secure the painting with either metal tabs that are provided with the frame or a 1/4-inch staple gun. Place on your backing and install the hardware required for hanging.
Buying a mat that is not qualified as "archival" can lead to serious damage to your painting. Be sure to check the labeling for the mat.