It is difficult to face the quandary that is posed by owning a rare work of art or photograph that cries out for exhibition. In order to keep the item safe and in good condition, it must be properly stored in an acid-free, lignin-free, pH neutral box in a cool, dry and dark environment. On the other hand, if it is stored away, nobody can see and enjoy it. Proper matting, framing, and display of items can provide both enjoyment of and a high degree of protection for them.
Preservation matting involves several layers which make up a "mat packet." They consist of a back mat, the piece of art, and a mat with a window, called the "inner mat" or the "inner front mat." This packet can be used to store pieces of art or photographs when they are not on display. When in storage, a piece of acid free paper is often laid on top of the inner front mat as a dust cover. Most mat packets are stored flat, in acid free boxes. The packet itself will act as protection for the item, so mat packets can be stacked inside their storage boxes.
Preservation framing adds several layers to the mat packet. It will add an additional backing board to protect the mat packet from the outside world. It might add another mat with a window, usually a highly decorative mat, one which complements the art. This is called the "outer mat" or the "outer front mat." The frame will have UV protective glass or acrylic as the glazing.
Some mat packets will include both the inner front and the outer front mats. This is especially true if the mats are designed to complement each other and the art. The inclusion of both mats will add some protection to the art itself when being stored.
How to choose a frame
The two main materials used for frames are wood and metal. Hardwoods are better than soft woods for framing, as they contain fewer acids that are harmful to paper. However, with preservation matting, no part of the frame will touch the art. It is not recommended that art or photographs be stored or displayed for long periods in a wooden frame. All types of metal are acceptable for framing art or photographs. Keep in mind that any backing or precut mat that comes with a frame will not be suitable for preservation matting.
In selecting a frame, be sure to choose the right size. As the item is to be matted, it is a good idea to get a frame that is at least two inches larger on each side of the item. For example, the frame for an 8x10 photograph would be 12x14. Larger frames accommodate wider mats.
Frames that are made to order at art supply stores are one option. However, these are not the only style that can be used for archival matting of art or photographs. The pre-made frames available at art supply and department stores are also useable for archival framing. Do not buy the kind of frame which has a fixed back that requires the items to be slid in from the top. The type of frame you will need must have a deep rabbet (see below) and must allow you to access the entire opening of the frame.
For pre-made frames, look for the style of frame that permits the backing to come away completely, allowing access to the glass. There should be some method of holding the mat packet in place on the back of the frame. Some methods include U-shaped brads or large staples that lift up with the help of a flat screwdriver, or curved metal strips that tuck into the corners of the frame back. The mat packet should be well supported around the inside edges of the frame back. If there is no method inherent with the frame, then framer's points will need to be used to keep the mat packet from falling out. Framers points are flat, diamond shaped pieces of metal that are shot into the rabbet with a point driver.
Glazing, mats, and backing board
The glazing used should either be glass or acrylic (Plexiglas, Lucite, etc.). Both come in UV protective versions. Glass is best used for art that has a friable media, such as pastels, charcoal, colored pencil, and the like, as acrylic can build up a static charge which can lift the media from the paper. Glass can also be better for photographs.
The backing which comes with pre-made frames is completely unsuitable for use in archival framing. However, it is usually the correct size. It can be used as a pattern for cutting the front mats, the back mat, and the backing. All of these items should be acid free, lignin free, and pH neutral. Foam core, wood, and cardboard are popular materials used in framing items, but they contain acids or other dangerous chemicals that are harmful to the art.
The artwork itself will be sandwiched between the decorative front mats and the back mat. The front mats can be made of cotton matting board, which is available in many colors at art supply stores. Photographs are best double matted to be sure there is a sufficient space between the glazing and the emulsion of the photograph, as photographs easily stick to glass in humid weather. Double matting is also a good idea for friable media, such as pastel, charcoal, pencil, and colored pencil, so the glazing has no chance of smearing or touching the art. Choose two colors of mat which complement each other and the artwork.
Many framing centers use spray adhesives or dry mount to attach the art to a backing board. This is not safe for your art. It will make it very difficult to take the art off the backing board, if ever you want to, nor will it last forever. Although it prevents the art from buckling when first mounted over time the adhesive will become dry and brittle, allowing the artwork or photograph to come free. Spray adhesives and dry mount are also somewhat acidic and can stain the back of the art or photograph. Over time it might even leach through the paper and discolor the front. The adhesives used in archival matting and framing are either acrylic based or are made from wheatstarch paste. Acrylic based linen tape is a good solution for attaching a photograph or piece of artwork to a backing.
For a more in-depth look at preservation matting, see "How to mat a piece of art."