in a step-by-step manner while leaving them intact over and beyond the next
split. For larger panels, which may tend to move substantially on release, a
cross-grain direction of removal may be adopted. The panel can move and
warp more freely across the wood grain, with less chance of twist than if
removal proceeded irregularly or from an end-grain edge. A hand-pressured
chisel (no mallet) and a dovetail saw were the only tools used.Curvature effects and rejoining of larger panels
The convex warp (viewed from the painted side) in many panel paintings
is largely due to the development of compression set (Buck 1972:2), as
shown by both panel examples.^47 Both were rejoined with respect to the
set warp assumed by the planks after removal of the reinforcements.
Several methods might be considered to reduce such warp and maintain
the panel in a safer, more planar configuration. Though usually done for
aesthetic reasons, this would also lessen the panel’s tendency to buckle
under its own weight if the planks are disposed horizontally.
In the author’s opinion, set in the wood of panel paintings is not
practically reversible as yet, especially in larger panels, because most meth-
ods involve extensive intervention to the wood or have uncertain long-term
effects.^48 Raising the ambient humidity provides only a temporary reduction
in warp, because the effect of set warp in a panel equilibrated to one
humidity returns if the panel is placed in a higher humidity and allowed to
fully equilibrate. The impression of an apparent reduction in warp from
raising ambient humidity is especially evident with larger panels because of
their greater total movement. However, most observers do not have the
opportunity to monitor long-term changes in larger panels under controlled
environmental conditions until an equilibrium curvature is established.
Other methods of warp reduction are possible. As the Mengs
required extensive rejoining, V-shaped inserts could be used in the joints
tocounter the curvature of the planks and achieve a relatively flat panel
(Fig.15). This method has been used for panels ofall sizes, sometimes for
aesthetic reasons. However, a gentle overall curvature may be less disrup-
tive to the appearance than the resulting “washboard.” Photographs before
and after structural treatment of the Palmezzano, in raking light, may be
compared in this respect (Fig. 16a, b).
Insertion of wedges for the purpose offlattening the panel may
be considered as a last resort, whether for structural or aesthetic purposes.
Acceptable flatness is partly an aesthetic concern, of course. In general,
however, it may be preferable to respect the current overall curvature, as
determined by the original panel structure and aging effects, to preserve
intact joints and the painting in unaltered form. Panels that are partially
disjoined or split, such as the Mengs, would require either breaking the
remainder of the fractured area, with serious risks to the overlying and
adjacent paint, or inserting wedges into the parted areas as desired.
Additional stress would be imposed on the remaining intact joint or sound
wood as flattening pressures were applied. From an ethical standpoint,
such an option for flattening is more practical and possibly more accept-
able for a complete disjoin.
For both panels, the above options for flattening would all involve
protracted and serious risks. Finally, breaking of a partial disjoin having
original, intact paint above is an important ethical issue. In consideration
ofthese points, the set warp and its ramifications were accepted in the466 Brewer