- Reinforcement of the addition by the insertion of several
rectangular wooden pieces to hold the two parts of the
join together. - Construction of two temporary crossbars to hold the painting
during the removal of the existing crossbars. - Gradual removal of the existing crossbars.
- Repair and correction of the separated edges by the cutting of
tracks with a V-shaped section. - Leveling of the painted surface along the edges of the indi-
vidual planks. - Exact fitting and placement of the wedge-shaped inserts, to be
made ofold wood (ofthe same type as the support), into the
specially prepared V-shaped tracks. - Construction of a laminated oak framework that has a load-
bearing function and also controls the deformation of the
planks that make up the support. - Development of a plan for the microclimate control of the
back of the panel.
Restoration interventions
Fumigation
The painting was fumigated in a gas chamber without vacuum, and then
protected on the back with Permethrin, a fumigant that remains active.Consolidation of the wooden material
Before the removal of the crossbars and the wooden blocks of the previ-
ous restoration, the join between the two sections of the support, which
was in danger of separating, was reinforced. The technique used for this
operation consisted of placing twelve rectangular inserts, made of the
same wood as the support, on edge in the same grain orientation as the
fibers ofeach plank, positioned across the horizontal junction. These
inserts were distributed in the grain direction of the planks, penetrating
the thickness of the support to within 5 mm of the painted surface. Thus
the inserts reunited the two elements of the lap join.
One of the more problematic aspects of this restoration was the
need to regain sufficient strength in the areas of the wood that were
degraded by biological attack. The choice of consolidant was proposed in
consideration of the uncertainties consolidants had generated in the past
in the Florence laboratory; particular concerns were the efficacy of con-
solidants and their possibly negative effects over time. These concerns are
tied to the stability of the product, possible color alterations, and nonuni-
form penetration into the wood (so that different areas of the wood are
conditioned to respond differently to variations in RH). In this case, how-
ev er, it was decided to use a 5–12% solution of acrylic resin (Paraloid B72)
in lacquer thinner applied by brush until a sufficient consistency was
reached. Before this operation began, all the hide glue and sawdust fillings
were removed from the support, and two temporary crossbars were made.
These crossbars were modeled to the curvature of the painted surface to
support the panel adequately and make it possible to work on the back.
The removal of the wooden blocks that held the existing cross-
bars followed; this procedure freed the entire back surface of the support
and prepared it for the initiation of the consolidation technique. Repair and322 Castelli