author aligned the planks according to a regular curvature that followed
the individual deformations of the planks and that took into account both
the visual unity of the work and its structural needs. This operation was of
critical importance and required a lengthy time for study and the prepara-
tion ofdifferent simulations to help determine the proper equilibrium
between the deformations ofthe individual planks and the general curva-
ture that derives from them. When the correct equilibrium was reached
between the curvature and a good visual unity of the work (with its place-
ment in the original frame considered), two temporary crossbars were
made that served as a reference during the final assembly phase.
Another difficulty was the need to bring together at an equal level
the painted edges between the individual deformed planks. Through
observation of the defects that emerged in this painting, it was possible to
confirm that the deformations that appeared are not casual ones but
clearly respond to the composition and direction of the grain and, more
particularly , to the arrangement of the tree rings in the planks. This infor-
mation also confirms that the planar stability of a painting hinges on a
careful selection of wood at the time of construction.
The author and coworkers then began work on rejoining the
panel from the two central planks, starting from the center and moving
toward the outside, using the already described crossbars as a reference,
and proceeding gradually both with the leveling of the painted surface
and with the gluing of the wedges (Fig. 21).^20 The remaining parts of the
painting were reassembled with this same method (Fig. 22).
After this phase, a crossbar system was built that was identical
to the original in both the kind of insertion used for the crossbars and
the mode of function. This system, which appropriately limits the expan-
sion and deformation over the entire surface, seemed the most suitable
for the state of conservation of the pictorial surface of this particular
work. Movement is controlled by the friction encountered by the crossbar
within the tapered, trapezoidal shape of the track in the support (panel).
Conversely, the elasticity of appropriately sized crossbars controls defor-
mation. To function appropriately, the crossbars were made with a curved
profile, part ofa circle that follows the curvature of the support. ThisT R P P S: S C H 333Figure 20
Francesco Salviati, The Deposition from the
Cross. Wood-block system used to fillinthe
tracks ofthe original crossbars.