Matting a picture for framing means cutting a window mat that overlaps the artwork by at least 1/8 inch on every side while the mat board itself creates protective space between the art and the glass.
Cutting a window mat—the piece with a rectangular opening that sits on top of your artwork—protects the piece and gives it a professional gallery look. A proper package uses a window mat plus a rigid backing board, both made from conservation-grade materials. Doing it right keeps your art safe for decades; doing it wrong can damage the piece permanently.
Choosing Conservation-Grade Materials
Standard 4-ply board works for most pieces. If you are framing photographs, the board must pass the Photographic Activity Test to prevent chemical reactions with the image.
For the backing board, the Library of Congress recommends acid-free, lignin-free corrugated board or corrugated polyethylene/polypropylene at least 3 mm thick. This rigid layer supports the package and keeps the artwork flat.
Many craft-store mats labeled “acid-free” meet these standards, but check the label for cotton rag content. Museum-grade cotton rag board costs more than wood pulp board but offers the best long-term protection.
Cutting the Window Opening
The window opening must overlap the artwork by at least 1/8 inch on each edge. Without this overlap, the artwork edges peek through the opening or fall into it entirely, which looks sloppy and leaves the edges unprotected.
To cut a window mat, you need a straightedge, a sharp mat cutter, and a cutting surface. Measure your artwork first, then add 1/8 inch to each dimension for the overlap. Mark the window dimensions on the back of the mat board, score along your lines with the cutter, and complete the cuts through the board thickness. Practice on scrap board first—clean corners require smooth, continuous cuts.
The frame’s rabbet (the inner lip holding everything in place) must be deep enough to hold the full package.
Attaching the Artwork Without Damage
The Library of Congress recommends non-adhesive hinging whenever possible. Mounting corners, polyethylene strapping, or Japanese tissue hinges with refined wheat starch paste all hold the artwork in place without putting adhesive on the image itself.
Never use spray mount, rubber cement, adhesive tape, or pressure-sensitive backing to attach paper to the backing board, warns the New York State Archives. These adhesives can stain, discolor, or chemically degrade the artwork over time, and removal often damages the piece.
For most home framers, photo corners are the simplest safe option: slip each corner of the artwork into a Mylar or paper corner, then attach the corners to the backing board. Japanese tissue hinges work well for larger pieces but require practice applying wheat starch paste correctly.
Assembling the Frame Package
Assemble the package in this order: backing board, artwork attached to it, window mat on top, then the glazing. The mat’s thickness creates the crucial air gap.
Standard glass offers no UV protection and can fade artwork over time.
Secure everything with pins or brads where conservation guidance specifies—never tape.
Before buying supplies, check what framing materials suit your specific art size. If you are working with a common size, our roundup of the best 16 x 20 frames with mats shows pre-cut options that skip the cutting step entirely.
One presentation note: photographers often make the bottom border slightly wider than the top to visually center the image. This is a style choice, not a conservation requirement—either look works.
Common mistakes that damage art include using non-archival foam board, letting the artwork touch the glazing, applying adhesive directly to the image, and cutting the window too large so edges show through. Avoiding these four errors puts you ahead of most home framers.
References & Sources
- Library of Congress. “Matting and Framing for Works on Paper.” Details conservation-grade board specs and non-adhesive attachment methods.
