118 Uzielli
unheated) in central Italy might have been 12–16% (corresponding to typi-
cal air temperatures of 0–30 °C and relative humidities of 60–80%).^15
Inexceptional cases, insufficientl y seasoned wood was used, as
exemplified in the otherwise unexplainable width of gaps (a total of 4 cm
over the panel’s width of 293 cm) between the boards of Duccio’s Maestà
(Fig. 8) (Del Serra 1990).Size of boards
Most of the supports were made of two or more boards, depending on
their size and shape. Only smaller supports were made of a single board.
No general rules may be given on this subject since there is obviously
great variability. Boards as wide as 60–70 cm or wider have been occasion-
ally used, although 20–40 cm is the more common range of width.
Using wider boards would certainly have reduced the number of
joins required for a panel and the consequent risk of separation along the
glued joints. Thicker boards confer greater strength and rigidity, as well
as greater dimensional stability under rapid environmental fluctuations.^16
However, disadvantages arise from their greater weight, greater manufac-
turing difficulties, and often unrestrainable forces that develop following
environmental changes, possibly leading to severe distortions or damages
(Uzielli 1994).
Typically, the original thickness ofboards ranged between 30 mm
and 45 mm, the thickness of large supports in particular being kept to a
minimum to reduce total weight.^17 Larger boards usually required a
gr eater thickness because ofmanufacturing techniques and the need to
conserve planarity.
Strength and planarity of earlier and more complex panels were
usually entrusted to the supporting system (frame, crossbeams, slats,
braces, etc.), thereby reducing the need for proportionally thick boards in
large paintings; in fact, 30 mm thick boards were often used. However, the
boards of some larger supports from the fifteenth century feature greaterFigure 8
Duccio, Maestà. Uffizi Gallery, Florence. Gaps
between the boards caused by seasoning
ofwood after the panel was manufactured
and painted.