CCI Notes 1/9

Low-Cost Plastic/Aluminum Barrier Foil

Introduction

Wood¹ used to make supports or containers for artifactsis often sealed with commercially available aluminumbarrier foils. This Note describes a low-cost method formaking a similar product from readily available plasticand aluminum foil.

Use of Plastic and Aluminum Barrier Films

Wood emits volatile organic compounds that can harm some materials (such as metals); direct contact with wood can also stain objects (Tétreault 2003). To prevent these problems, it is generally preferable to use materials other than wood when making supports or containers for artifacts. However, in many instances wood is still chosen because it is strong, rigid, readily available, easily worked, and relatively inexpensive. If wood is used, it should be sealed to prevent unnecessary damage.

Wood can be easily (although sometimes inefficiently) sealed with paints. However, oil-based paints are not recommended because they emit high levels of organic acids, and they should certainly never be used inside enclosures (e.g. display cases or storage cabinets). Even recommended paints, which include emulsion paints (i.e. latex), two-part epoxies, two-part urethanes, and shellacs, emit some harmful organic compounds. When these are used inside enclosures, they should be allowed to dry for at least 4 weeks to allow all the possible harmful compounds to evaporate (Tétreault 2002).

As an alternative to painting wood, plastic-laminated aluminum foil can be applied as a seal or barrier. Plastic-laminated aluminum foil is one of the best vapour or gas barriers on the market (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. The nylon side is usually shinier than the polyethylene side and often has the brand name printed on it. 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 fairly low temperature, about 170ºC (335ºF), domestic 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. Any holes or tears can easily be repaired by ironing a patch of the same aluminum barrier foil over the damaged area.

Another option to attach the plastic-laminated aluminum foil to wood is double-sided tape. Apply the tape in a grid pattern to ensure that the foil is attached uniformly over the entire surface area.

Once applied, the surface of the plastic-laminated aluminum foil is susceptible to scratches. However, because the surface is usually covered with layers of padding and fabric or matboard (Figure 1), this does not generally cause problems.

Figure 1. A panel covered with plastic-laminated aluminum foil, polyester batting, and fabric.

Low-Cost Alternative

A low-cost alternativeto commercial productssuch as Marvelseal can becreated using aluminumfoil and polyethylenegrocery bags, garbagebags, or sheeting (lookfor the triangle recyclinglogo with the letters LDPEor the numeral 4 to ensurethe plastic is low-densitypolyethylene) (see Figure 2).

Low-density polyethylene recycling logo.
Figure 2. Recycling logo for low-density polyethylene.

To protect the aluminumfoil from tearing whenassembling the barrier, insert a paper sheet betweenthe iron and the foil, as shown in Figure 3. If the plasticsheet is thin, up to 3 layers may be needed. Plainaluminum foil is even more susceptible to scratchesthan commercial products that have a nylon covering,so special care is important. However, if scratches orperforations do occur, they can be easily repairedby ironing on a patch of the same aluminum foiland polyethylene.

Applying aluminum foil barrier.
Figure 3. Applying an aluminum foil barrier with an iron, paper, aluminum, plastic, and wood.

Endnotes

¹Includes wood products.

Bibliography

Bosworth, J. "Retrofitting Old Exhibit Cases: A Search for Economic and Safe Cabinetry." Exhibitionist 20 (2001), pp. 20–24.
Burke, J. "Vapour Barrier Films." WAAC Newsletter 14 (May 1992), pp. 13–17.
Phipps, H. "Microenclosures for Framed Collections." Exhibitionist 20 (2001), pp. 37–40.
Tétreault, J. "Oak Display Cases:Conservation Problems and Solutions."
Tétreault, J. Coatings for Display and Storage in Museums. CCI Technical Bulletin, No. 21. Ottawa: CanadianConservation Institute. 1999.
Tétreault, J. "Guidelines for Selecting and Using Coatings." CCI Newsletter 28 (2002), pp. 5–6.
Tétreault, J. Airborne Pollutants in Museums,Galleries, and Archives: Risk Assessment, Control Strategies, and Preservation Management. Ottawa: Canadian Conservation Institute, 2003.
Thickett, D. "Sealing of MDF to Prevent Corrosive Emissions." The Conservator 22 (1998), pp. 49–56.

by Jean Tétreault

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