Make your matted prints in standard sizes, such as 5 by 7, 8 by 10, 11 by 14 and 16 by 20 inches. The clear acetate bags are designed only for standard-size pieces.
Include a thin backing board behind your artwork for stability. Make sure it's 1/8 inch or less wide so it'll fit into the acetate bag. This board can be cardboard or acid-free board and will most likely be thrown away after purchase.
Purchase clear acetate plastic bags made specifically for matted prints; match them to the sizes of your prints. You can purchase the bags at arts and crafts stores and from online supply stores.
Place the matted print inside the bag. The bag will have an adhesive flap to seal in the artwork. Though the adhesive should not permanently stick to the artwork, when the piece is removed, the back should be facing the adhesive side.
Purchase the shrink-wrap materials from an arts and crafts store or online. This will include a roll of clear cellophane, a heat gun and a sealer.
Place the matted print inside the roll of cellophane, pushing it up against the one or two sealed edges. Cut the remaining two or three sides, leaving two inches from the edge of the mat.
Seal the open sides of the cellophane bag surrounding the matted print. There should be no openings, and the print should be able to move around inside the clear bag.
Use the heat gun to shrink the cellophane over the matted print. Hold the gun at least 6 inches from the piece. Move the gun in a circular motion until the cellophane starts tightening on the piece. Turn the artwork upside down, and repeat for the other side. Hold it and focus on any spots that need tightening. The matted print will be completely sealed in a tight covering.
Find a box that is 1 to 2 inches larger than your matted print. Boxes made for artwork are available and include a protective barrier that protects the print from damage (see Resources).
Cover your matted print with a cushioning product, such as bubble wrap.
Place the protected artwork in the box and fill in any gaps will filler, like newspaper or tissue paper, to keep the print from moving around the box. Write "fragile" or "bendable materials" on the outside of the box for extra protection.