by Ingrid Rose
Ingrid Rose Paper Conservation LLC
In order to minimize future risks to the artifact, the use of permeable, pH-neutral materials is recommended.
: Ideally, conservation glass with UV inhibitor.
- Window Mat
: Neutral 100% cotton rag board, 4-, 6-, 8-ply or deeper. In case of float hinging, the artifact will be protected against direct contact with the glass by means of a spacer, 8-ply or deeper; rag board strips are preferred over impermeable plastic strips because the latter will prevent necessary off-gassing and may cause mold growth. “Neutral” rag board is stressed because a buffered bleach (as opposed to the more customary acidic hydrolysis or "mat burn".
: Japanese paper hinges, adhered with wheat starch paste or methyl cellulose or a mixture of both.
- Back mat
: Neutral 100% cotton rag board 4-ply. The window and back mats can be joined with linen tape, the adhesive of which tends to dry out. Joining these two elements with any type of pressure sensitive tape will preclude the necessary air circulation and off-gassing in that area, and can lead to mold growth.
- Backing board
: Archival, lightweight board: in case of dampness, an impermeable sheet (e.g. Mylar) between the back mat and backing board or between the backing board and dust cover will deflect moisture. The impermeable sheet should be flush with the edges of the mat sandwich. Bump-ons will ensure air space between the frame and the wall: cork pieces cut to a desirable length will increase air space and reduce dust outllines on the wall. Incidentally, boards with a petroleum-based core, e.g. foam core, may impede ventilation and act like fuel in case of fire.
- Dust Cover
: A sheet of neutral paper, adhered to the frame with an adhesive of choice. Indication of the date of framing on the dust cover serves as a reminder to test the mats for acidity, and periodic replacement. A dust cover also protects the artifact from insect migration.
Avoid sealing the matted artifact to the glazing with impermeable tape (i.e. any kind of pressure sensitive tape). If sealing is desired, a water based paper tape (i.e. the traditional kraft paper) may be used. A generously cut mat will reduce if not eliminate lignin migration from the wooden frame, as will coating the inside of the frame. A space of 1-2 mm (less than 1/16 inch) between the mat package and the inside frame (rabbed) will allow air to circulate freely, providing needed ventilation. Finally, a reminder that the bright light in our region is very strong and harmful to pigments and cellulose.
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