The Structural Conservation of Panel Paintings

reconstruction of the structure proceeded with the reintegration of the

missing parts of the support, in particular in the lap join. For this operation,

small blocks of old wood (of the same type as the support) were placed in

superimposed layers that intersected in width and length (Fig. 7). The use of

this method makes it possible to firmly bond the various wooden elements

ofthe reintegration and, in addition, favors increased stability by reducing

to a minimum the possible deformation of the added material.

The repair and rejoining of the separated joins and cracks were

carried out by the cutting of triangular tracks into the support. These

tracks conformed approximately in width and depth to the extent of the

degradation in the areas of the join edges.^8

The tracks were cut by hand with chisels (the traditional and

effective method to rectify gradually the degraded condition at the edges

of each plank), but wherever the consistency of the wood was good

and the split was straight, an extremely narrow, cone-shaped router bit

(5 mm maximum diameter) was used in order to remove as little original

wood as possible.

Successful experiments had already been performed with this bit,

made expressly for our laboratory, on samples that simulated V-shaped

openings in panel paintings. As usual, in the preparation of the wedge for

gluing, the surface levels along the joins and splits were aligned with the

help ofwooden levers. These wooden levers bridged the edges of the frac-

tures and were adjusted with screws and wooden blocks. This step was fol-

lowed by the fitting of the wedges, which were made from old wood (the

same type as the support). Care was taken to ensure that the positioning

ofthe grain was consistent with the grain at the edges of the opening.

During this work phase, the undulation of the painted surface, caused by

the curvature present in the two central planks, was slightly corrected, so

that part of this deformation was distributed over the entire width of the

painting. This operation has been shown to be useful in reducing the

deformations visible near the joins and in improving painting readability.^9

The correction of the edges produced an average curvature of 9 mm over

the entire painted surface. It is not useful to plot deformation measure-

ments without considering the ambient RH, because the wood is in con-

stant equilibrium with the surrounding microclimate and consequently

T R  P P S: S C H 323

Figure 7
Domenico Beccafumi, The Coronation of the
Virgin. The integration of missing parts in the
support with blocks of old wood.