departments of the Vecchie Poste at the Uffizi and Palazzo Pitti before
theflood, proved to be the most stable wood, with the least tendency to
deform (see Rothe, “Critical History,” herein).^1 Used for more than forty
years in the construction of crossbars, mansonia functions very efficiently
and, in fact, appears to be better than any other type of wood because of
its density and workability. Panels with mansonia crossbars expanded and
contracted drastically after the flood but did so with little or no buckling.
Planks ofmansonia that had been immersed for over a week and then
inadvertently used as gangways to wheel mud out from the ground floor
of the Vecchie Poste did not deform or crack, and they were later utilized
to make new crossbars. Today mansonia is still used—although much less
often because of its toxic properties. Other woods, such as steamed beech,
have also been used but have not given such satisfying results. Metal cross-
bars, such as those used successfully in Rome by the Istituto Centrale del
Restauro, have rarely been used in Florence, primarily because of aesthetic
considerations (see Rothe, “Critical History,” herein).
If a panel is in good condition, the conservator usually chooses not
to intervene. Unfortunately, this is not always possible. Intervention is nec-
essary whenever the original crossbars have been lost (causing warpage),
the panel has previously been thinned, splits have caused loss of color, or
panels have cracked apart. The restraint that a brace or crossbar should
exerton a panel is difficult to measure or predict, but today the rule is to
give the panel ample lateral freedom to move and to manipulate the origi-
nal surface as little as possible by making the braces much smaller than was
formerly considered appropriate, and thus more flexible (Figs. 1, 2).
Excessive restraint such as that caused by older cradles tends to
block the movement and facilitate the formation of new cracks and even
ofsplits (Figs. 3, 4). Conversely, too little restraint can allow panels to
deform, especially those that have been thinned and have lost their original
coating (see Rothe, “Critical History,” herein) or the aged “skin” thatF S S T 307Figure 1
Guglielmo di Pietro de Marcillat,
Annunciation,1524. Reverse. Oil or mixed
technique (?) on panel, 180 3 150 cm.
Convent of S. Francesco, Sargiano, Arezzo. A
typically heavy crossbar of the early 1970s,
with pegs glued and screwed to the panel; a
wide swath of original wood surface was
removed to create a level area. The crossbar
on the bottom is original.