Discover the common backing plates used for framing and mounting images. Why You Should Choose One Backing Material Over Another. Understand the properties of foam boards, Corflute, MDF, Masonite or hard boards, electronic boards and other cardboard. Which makes one more suitable than another when it comes to framing images.

Is foam board the best backing for framing photos?

All framed images require some type of backing material to provide rigidity and protection. Even stretched canvases that are not framed should have some backing to prevent dust from collecting on the back of the painting. When dust accumulates, it helps trap moisture, which promotes mold growth, which in turn damages the artwork.

Picture framers have used many types of backing boards over the years. Foam boards or foam core boards have become one of the most popular options recently due to their lightweight construction, rigidity, and easy cutting. They replaced the cardboard, Masonite, or MDF (medium density fibreboard) that copywriters had become used to using, but are better than their counterparts.

What often worries copywriters the most are the chemicals that can seep out of the image backing. Picture framers often talk about acid-free, lignin-free, or 100% cotton rags in their presentations to clients. Harmful chemicals in materials that are not acid-free can cause staining and acid burns on prints, posters, and artwork that they come in contact with. Sometimes protective layers such as barrier papers, mounting boards or polyester sheets are placed between the backing and the image. It is far better to remove the source of the harmful chemicals than to simply try to slow their migration into the artwork.

There are acid-free and cotton-topped foam boards that are sold as preservation foam boards, but they should be used with caution when used as a direct backing for artwork. One type of foam board made by Gilman USA is 100% plastic and could be considered a preservation board, but normally you would add another layer of 100% cotton rag board or an alpha cellulose board as a barrier. Many galleries prefer to use corflute due to its inexpensive cost and, again, being a plastic product, lignins are not present. Other preservation media include smooth surfaced corrugated board that is made from alpha-cellulose. A new development in E-flute core board production, where there is a double laminate corrugated core lined with acid-free white surfacing papers, is eagerly awaited by the framing community.

The use of plastic-based boards can have other effects that must be carefully weighed depending on the artwork being framed. Some plastics release plasticizers and other solvents that can cause irreversible organic changes in some paints, photographic emulsions, and substrates.

MDF or medium density fibreboard is popular for wet gluing and mounting of prints and posters, and is often used by copywriters to wet mount cheap mass produced canvas artwork. The benefits of MDF are its rigidity and low cost, but it is a very hygroscopic product so it tends to absorb moisture. Increased humidity promotes mold growth and can also cause staining of the image by drawing chemicals on the front of the artwork. It can also sag due to expansion of the backing, but this can be rectified by cross-laminating or sealing the backing with a waterproof varnish. If the artwork or poster is for decoration only and has no long-term value, MDF is an inexpensive substrate to use.

The straw board was used by picture framers throughout the 19th and mid-20th centuries. The straw board was made of straw and had a yellow appearance. It offered some benefits due to its alkaline nature, and editors glued prints and watercolors onto it with rabbit fur glue or pearl glue. The pearl glue was a glue made from gelatin and was applied in a hot water bath. Ancient writers sometimes added mercury salts and other fungicides to the mix in an effort to prevent mold or fox formation. In some ways, these methods were better than when the invention of PVA glue appeared. At least one old print could be lifted with a gentle soak, but with the advent of PVA, the images were permanently attached to the backing.

In addition to framing disposable decorative items such as mass produced posters, it is wise to consider using reversible framing techniques. Most of these techniques involve attaching the image to the backing board using Japanese paper hinges or some other acid-free archival tape. If you choose the reversible method, at least the image can be removed from the frame and has the potential for easier restoration or preservation in the future.