The Structural Conservation of Panel Paintings

section protruded in front of the panel by 5 mm to enable the block hold-

ing the roller bearings to be set in the line of the center of gravity of the

panel. The blocks of aluminum were bolted to a strip of 6 mm aluminum,

which was bolted in turn to the L-shaped aluminum section to increase

rigidity. The bearings run in the slots cut in the bottom rabbet of the

frame, which are lined with stainless steel strips to prevent the bearings

from denting the wood and locking the system. When upright, the panel

rests on the bottom edge of the frame and against shaped rabbets on

either side. The panel is held in the frame across the center by two hori-

zontal battens resting on the panel battens and attached to the frame by

bolts and compression springs to allow some movement in the event the

panel should assume a less convex profile (Figs. 10, 11a, b).

When received for treatment, the three elements of the triptych—a central

single poplar panel of the Madonna and child, flanked by panels of two

vertical planks with arcading attached above—were held together by three

battens screwed to each panel in turn (Hamilton Kerr Institute 1984)

(Figs. 12, 13). At the front, the decorated base was screwed to the lower

edges of the panel. This rigid construction, probably made in the late

nineteenth century in France, as the provenance suggests, had caused the

opening of splits in the left and right panels and twosplits in the central

panel. The two columns separating the wings from the center were con-

temporary with the rest of the frame.

The components of the altarpiece were dismantled. The battens

were unscrewed and the columns and pilasters gently prized off. Anew

framework to hold the panels was constructed from pine, stained to be

unobtrusive, and then sealed with polyurethane varnish to reduce dimen-

sional change in the structure (Fig. 14). The frame’s base was adjusted

with balsa-wood spacers to hold the three panels at the correct alignment

(Fig. 15). Each outside panel was attached by the base of the support and

by a shaped brass strip fixed to the back of the framework at the upper

rail. The central panel was similarly attached at the base and attached by

steel hooks to existing original fixings in the panel above the pilasters. Two

vertical strips of wood were placed over the joins between the central

panel and the outer panels and were held in place by stainless steel bolts

Triptychattributed to

Pietro Gerini

442 McClure

Figure 10
Anton Raphael Mengs, Noli Me Tangere,1771.
Reverse. Oil on walnut panel, 291.5 3 178.5
cm. All Souls College, Oxford.