The Structural Conservation of Panel Paintings

Eventually the success of this backing system suggested that it could be

used safely to reduce deformation in warped panels without thinning and

channeling, as was done at the Fogg Museum. This process is accom-

plished by exposing the panel to moisture at the back surface until

sufficient flattening has occurred. The Saran and fiberglass cloth layer is

then applied, and while the panel is flat, the wax and balsa blocks are

added (Buck 1972). The backing acts as a mechanical restraint while the

panel, which has been flattened by exposure to moisture, slowly dries and

undergoes relaxation of stress. This extension of the basic backing obvi-

ously adds many uncertainties and complications and was not a technique

Buck frequently practiced. A painting treated by this method in 1967 (Buck

1972) has been examined recently; it remains in stable condition in its

flattened state. At least one other flattening by this method has been pub-

lished, with good results (Reeve 1981).

It may be useful to review some of the principles involved in interpreting

the behavior of panel paintings, particularly as they illustrate the success

of this backing method. Buck has carefully presented the essential material

(Buck 1963, 1972); only a brief expansion on this framework will be

attempted here.

Wood is clearly a nonuniform and variable material, for which

sample differences can be of great significance. Certain consistent prin-

ciples, however, can be used to understand and predict its behavior. Of

particular importance is the relationship of wood and water. Buck demon-

strated that aged wood retains its hygroscopic nature over time (Buck 1952).

Moisture Movement and

Panel Paintings

Warp Reduction with

Balsa Backings

R B: T D  U   B B  P P 295

Figure 6
Back of a panel painting after cradle removal.

Figure 7

Fiberglass cloth and Saran F310 resin layer

added to the panel back.

Figure 8

Fiberglass cloth and Saran F310 resin backing

after drying.

Figure 9

Balsa-block backing in place.

Figure 10

Balsa block s trimmed and smoothed.