Discover common backing boards used to frame and mount 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 boards. Which makes one more suitable than another when it comes to framing pictures.
Is foam board the best backing for picture framing?
All images 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 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 or foamcore boards have recently become one of the most popular options due to their lightweight construction, stiffness, and easy cutting. They replaced the cardboard, Masonite, or MDF (medium-density fiberboard) that framers had grown accustomed to using, but they are better than their counterparts.
What framers often worry about most 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 in non-acid-free materials can cause stains and acid burns on prints, posters, and artwork they come into 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 harmful chemicals than to try to slow their migration into the artwork.
There are acid-free and cotton-surfaced foam boards sold as conservation foam board, but they should be used with caution when used as direct backing for artwork. One type of foam board manufactured by Gilman USA is 100% plastic and could be considered a conservation board, but would still typically add another layer of 100% cotton rag board or alpha cellulose board as a barrier. Many galleries prefer to use corflute due to its cheap cost and again, being a plastic product, lignins are not present. Other preservation media include smooth-surfaced, coated corrugated boards that are made from alpha-cellulose. The framer community is eagerly awaiting a new development in the production of E-flute core boards, where there is a double-laminated corrugated core lined with acid-free white surface papers.
The use of plastic boards can have other effects that need to 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 fiberboard is popular for wet-gluing and mounting prints and posters, and is often used by framers to wet-mount inexpensive 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 blemishes on the image by attracting chemicals to the front of the artwork. It can also sag due to expansion of the backing, but this can be corrected by counter-laminating or sealing the backing with a waterproof varnish. If the artwork or poster is just for decoration and has no long-term value, MDF is an inexpensive substrate to use.
Strawboard 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 with rabbit fur glue or pearl glue. Pearl glue was a glue made from gelatin and was applied hot in a water bath. Ancient builders sometimes added mercury salts and other fungicides to the mix in an effort to prevent mildew or scaling. In some ways, these methods were better than when PVA glue was invented. At least one early print could be lifted off 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 like mass-produced posters, it’s wise to consider using reversible framing techniques. Most of these techniques involve hanging the image on 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.