page at the molecular level in panels restrained flat by balsa laminates must remain theoretical
“until an occasion arises to remove the balsa backing from one of the panels and to observe
the actual behaviour.” (Buck 1972:11). Observations and an attempt to accomplish this process
under similar conditions have not convinced the author that flattening can be achieved by
higher MC and pressure alone. Gordon (1976:143) asserts that heat is the principal agent for
bending wood. Other key elements, however, are time and whether the desired effect can be
achieved within a practicaltreatment period. A combination of heat and moisture applied over
an extended period would subject most panel paintings to considerable risks.
Chemical methods, through vapor exposure or impregnation (for example, see Wolters
1963), either interfere physically with the moisture response of the wood or alter the chemical
nature of the wood. Both results alter the nature of the panel painting structure in ways that
have not been tested over long periods. Again, the risks seem prohibitive. The effects and
effectiveness offlattening methods should probably be investigated with controlled studies.
49 One method of rejoining uses wood inserts glued into V-section channels that are cut into the
panel back along the split or disjoin (Uzielli and Casazza 1994:21; Bergeon 1990:22).
50 Recall that even the strong original joints of casein parted—rather than the surrounding
walnut wood.
51 See, for example, the increasing frequency of articles on this subject in the journal OPD
Restauro(1986–93).
52 This is a recommended average RH level for wooden objects (Thomson 1978:85).
53 Another possibility to facilitate the use of such long battens or similar strips for large panels
is to construct the retainers from base blocks, glued to the panel, and a removable retaining
plate screwed or bolted to threaded metal inserts in the blocks.
54 Evostik Resin W, avirtually100% polyvinyl acetate resin, applied as a dispersion (Howells
et al. 1993).
55 As awarp ensues, a panel that is more flexible than a reinforcing batten, for example, per-
forms like a flexible reinforcement, so that the proper roles are reversed. Rather than the bat-
ten bending to conformto the panel’s warping movements, the panel’s warp is bent back on
itself to conform to the reinforcement. Thicker panels, being more rigid (other things being
equal), increase the friction against rigid reinforcements. When the friction exceeds the tensile
strength of the panel, the panel will break from the stress. Bending in panels involves stresses
of a more complex nature than can be discussed further here.Evostik Resin W,Evode Ltd., Common Road, Stafford, England.
Paraloid B72,Conservation Resources (U.K.) Ltd., Pony Road, Horspath Industrial Estate,
Cowley, Oxfordshire, England.Bergeon, S.
1990 Science et patience, ou La restauration des peintures.Paris: Editions de la Réunion des
Musées Nationaux.Bodig, J., and B. A. Jayne
1982 Mechanics of Wood and Wood Composites. New York: Van Nostrand Reinhold.Bomford, D., J. Dunkerton, D. Gordon, A. Roy, and J. Kirby
1989 Art in the Making: Italian Painting before 1400. London: National Gallery.Brewer, A.
1994a A consolidation/filler system for insect-damaged wood. Hamilton Kerr Institute
Bulletin2:68–72.1994b Aluminum devices as temporary helpers for panel structural work. Hamilton Kerr
Institute Bulletin 2:73–76.References
Materials and Suppliers
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