The benefits and drawbacks of different types of picture frame backing boards

Discover common backing boards used for framing and mounting pictures. Why you should choose one backing material over another. Understand the properties of foam board, Corflute, MDF, Masonite or hardboard, e-board and other paperboard. Which makes one more suitable than another when it comes to framing pictures.

Is foamboard the best backing for framing pictures?

All pictures that are framed require some type of backing material to provide rigidity and protection. Even stretched canvases that are not framed should have a backing to prevent dust from collecting on the back of the painting. When dust builds up, 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. Foamcore 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 fiberboard) that framers had grown accustomed to using, but they’re better than their counterparts.

What framers are most often concerned about are the chemicals that can leach from the backing into the image. Framers often talk about acid-free, lignin-free, or 100% cotton rags in their presentations to clients. Harmful chemicals from non-acid-free materials can cause stains and acid burns on prints, posters, and artwork with which they come in contact. Sometimes protective layers such as barrier papers, mounting boards, or polyester sheeting are placed between the backing and the image. It is much better to eliminate the source of harmful chemicals than to try to slow their migration into the artwork.

There are cotton-surfaced, acid-free foam boards that are sold as conservation foam board, but 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 preservative board, but typically another layer of 100% cotton rag board or alpha cellulose board would be added as a barrier. Many galleries prefer to use corflute due to its economic cost and, again, being a plastic product, lignins are not present. Other preservation media include smooth surface coated corrugated boards that are made of alpha-cellulose. The framing community eagerly awaits a new development in E-flute core board production, where there is a double-laminated corrugated core faced with acid-free white surface papers.

The use of plastic boards can have other effects that need to be carefully considered 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 fiberboard, is popular for wet-gluing and mounting prints and posters, and is often used by framers to wet-mount cheap, mass-produced canvas art. 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 image blemishes by drawing chemicals to the face of the artwork. It can also buckle due to expansion of the backing, but this can be corrected 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.

Straw cardboard was used by picture framers throughout the 19th century and into the mid-20th century. The straw board was made of straw and had a yellow appearance. It offered some advantages due to its alkaline nature and framers glued prints and watercolors together with rabbit fur glue or pearl glue. Pearl glue was a glue made from gelatin and applied hot in a water bath. Ancient builders sometimes added mercury salts and other fungicides to the mix in an effort to prevent mold or foxing. In some ways, these methods were better than when the invention of PVA glue came about. At least one early print could be lifted with a gentle soak, but with the advent of PVA, the images became permanently attached to the backing.

In addition to framing disposable decorative items like mass-produced posters, it is wise to consider using reversible framing techniques. Most of these techniques involve hanging the image onto the backing board using Japanese paper hinges or some other acid-free archival hinge 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.