The reverse side of the wood and stretched fabric (canvas) supports need protection from moisture and changes in relative humidity. A method described in a Canadian Conservation Institute Note and other conservation articles describes materials that artists can employ to protect their own work.
Plastic-laminated aluminum foil is one of the best vapor and gas barriers available (Burke 1992; Thickett 1998) and can be purchased from various distributors. One type commonly used by conservators is Marvelseal 360, an aluminum foil coated with nylon on one side and polyethylene film on the other. Plastic-laminated aluminum foils can be adhered to wood with heat. Place the polyethylene side adjacent to the surface of the wood and then apply heat with an iron or hot spatula. Because polyethylene melts at a reasonably low temperature, about 170º C (335º F), irons set to the "permanent press" setting are usually adequate to fuse the polyethylene to the surface beneath. However, the heat must be applied evenly to the entire surface to ensure proper melting and good adhesion.
Figure 1. Recycling logo for low-density polyethylene.
A low-cost alternative to commercial products, such as Marvelseal, can be created using aluminum foil and polyethylene grocery bags, garbage bags, or sheeting (look for the triangle recycling logo with the letters LDPE or the numeral 4 to ensure the plastic is low-density polyethylene) (see Figure 1).
To protect the aluminum foil from tearing when assembling the barrier, insert a paper sheet between the iron and the foil, as shown in Figure 2. If the plastic sheet is thin, up to three layers may be needed. Plain aluminum foil is even more susceptible to damage than commercial products with nylon covering, so special care is essential. However, if scratches or perforations occur, they can be easily repaired by ironing on a patch of the same aluminum foil and polyethylene.
Figure 2. Applying aluminum foil barrier.
Burke, John (1989) Microclimate Research at the Oakland Museum, WAAC Newsletter Vol. 11, No. 2 (May 1989), pp. 11-14.
Burke, John (1992) Vapour Barrier Films, WAAC Newsletter Vol. 14 (May 1992), pp. 13–17.
Tétreault, Jean (2011) Low-Cost Plastic/Aluminum Barrier Foil, Canadian Conservation Institute Notes 1/9.
Thickett, D. "Sealing of MDF to Prevent Corrosive Emissions." The Conservator 22 (1998), pp. 49–56.