State of preservation
The planks that make up the support show slight convex warping on the
painted surface. This phenomenon is greater on the outside planks, and
on the painted surface, a pronounced misalignment is noted at the open
splits. The central plank, from a radial cut, shows separation of the tree
rings in correspondence with the pith. The phenomenon of ring separa-
tion (the “onion effect”) is typical for chestnut but rare in poplar (Fig. 26).
Finally, the joins were open, and cracks were noted in the bottom part
of the support.Previous restorations
The last restoration carried out on the painting dates from the 1950s. On
that occasion, the paint layer was cleaned, and the gesso that had been
applied on the gilding of the architectural part was removed. To restrain
the planks that had separated, butterfly inserts were inset across the joins.
Some ofthe planks of the support were warped, so that a double convex
deformation was formed across the painted surface. To lighten the tension
in the planks, the crossbars were reduced in thickness. The upper one
was thinned though not removed from its housing, while the central
one was removed by the cutting of its original nails; it was then thinned
and put back into place with normal screws. Finally, in the case of the bot-
tom crossbar, it could be seen that the nails had been straightened and the
crossbar slipped off, r educed in thickness, and reattached with the same
elements, since the heads ofthe nails could be reached by removing the
smaller predella.Restoration proposal
The plan for the intervention was established after careful evaluation of
the condition of the painted surface, the consistency of the wood, the
uneven surface alignment at the splits, and the hold of the crossbars.
The removal of butterfly inserts was justified in that their func-
tion is only partial, and, in fact, they are even harmful, since the grain is
placed in the direction opposite to that of the support, so that tension
points are created between the planks.
The following were planned: repairing the splits with the wedge
technique, adjusting the surface level at the splits, overhauling the cross-
bars, and protecting the back with an antiwoodworm product based
on Permethrin.Restoration interventions
By use of an electric router attached to a pantograph template, the wal-
nut butterfly inserts were removed. This made it possible to obtain the
perfect refacing of the cavities on both the edges and the bottom. In this
case the author felt that the slight vibration of the instrument would be
well tolerated by the support and by the entire, rather solid preparation-
paint layer. The cavities were corrected and filled with small elements
ofold wood of the same type, and arranged in the same grain direction,
as the support.
The separated edges of the joins and cracks were repaired with
the traditional method: triangular-section blocks were custom-fitted into336 Castelli
Figure 26
Lorenzo Monaco,The Annunciation. Asplit
onthe back of the panel; some ring separa-
tion is evident in the wood of the support’s
central plank.