The correction of the tendency of panels to develop convex warps
when exposed to low ambient levels of RH is probably one reason for the
increasing popularity of cradling from the mid–eighteenth century into
the first half of the twentieth century. A panel would be thinned by the
introduction of moisture and become very responsive to flattening. A
cradle would then be attached, to restrain the panel in plane. In this way,
the visual disturbance caused by a gap between the frame rabbet and the
picture surface could be corrected. By the mid–nineteenth century, panels
were routinely thinned and cradled, and even as late as the 1960s the desir-
ability of a flat picture plane was cited as a reason for major intervention.^7
Today it is generally accepted that panel paintings should be allowed to
assume a natural warp at a given RH and that the frame should be
adjusted to suit such movement.
The principles behind early-twentieth-century solutions to the
problems of framing panels hardly differ from those we recognize today.
In 1936 in the National Gallery ofScotland, the wings of the Trinity
Chapel Altarpiece relied on the provision of a microclimate enclosure,
the exterior of which served as the frame (Cursiter 1936:109–16). In 1940
the International Office of Museums recommended, among other urgent
concerns, the use ofsteel springs in framing panels to allow movement and
added the proviso that they should be removed for transport (International
Office of Museums 1940:80, 81, n. 58, 59). In 1955 George Stout, as part of
the survey ofpanel treatments instigated by the International Council
of Museums Commission for the Care of Paintings, illustrated examples
of frames causing splits in panels and of panels causing the breaking of
frames. Several systems for fitting panels were illustrated, including a sys-
tem for supporting a panel with unglued cracks.^8 In 1965 Straub recom-
mended the use offlexible strips ofsprung steel to allow warping. This
apparatus could be combined with a backing to provide protection against
shock and to act a buffer against changing climatic conditions (Straub 1965).
Similarly, in 1978 Goetghebeur recognized the use of the picture frame to
support panels and suggested the use of sprung steel strips to allow move-
ment (Goetghebeur 1978). In 1982 Ranacher largely repeated Straub’s
recommendations (Ranacher 1982:147); the same year Vöhringer described
a framing system for a sixteenth-century panel which supported the panel
in the center and allowed movement at the edges by means of a leaf spring
held in place by a U-section metal bracket and adjusted by a threaded bolt
(Vöhringer 1982:fig. 9). In 1988 Dunkerton and coworkers described the
widening of the groove of a later double-sided frame housing the wings of
an altarpiece by Martin van Heemskerck (Dunkerton, Burnstock, and Smith
1988:20). Low-density foam was fitted in grooves on both sides of the panel
to allowsome movement. Hermesdorf, in 1989, described a system ofsus-
pending the panel on aluminium strips attached to the frame. Wooden
buttons, normally reinforcing reglued joins and splits, had slots cut in them
that fitted over the aluminum sections (Hermesdorf 1989:267–69). The use
of roller bearings attached to the base ofa support for a large panel with
horizontally aligned planks and running on tracks on the bottom rabbet
section of the frame significantly reduces static friction between the panel
base and frame, allowing the panel to move in response to changes in RH
(see Bobak, “A Flexible Unattached Auxiliary Support,” and Marchant,
“Development of a Flexible Attached Auxiliary Support,” herein).
These methods reflect the current belief that panel paintings
should be allowed to move, perhaps within limits, to adopt greater or438 McClure
Figure 8
Maso di san Friano (attrib.),Portrait of a Man
with a Watch,mid–sixteenth century. Reverse.
Oil on poplar panel, 117 3 92 cm. Science
Museum, London.