thickness and flexibility is fully explained in Marchant, “Development of a
Flexible Attached Auxiliary Support,” herein);^1 or applying self-adhesive
TeflonPTFE tape to the sliding battens to reduce friction.^2 If needed, in
addition to easing the cradle, other possible improvements include con-
struction of shaped slips for the frame that follow the panel’s profile;
assurance ofadequate retention in the frame even while it accommodates
some change in curvature without excessive restriction; fitting of back-
boards, which also offers additional physical protection and slows the rate
of moisture exchange; provision of microenvironments (such as microcli-
mate boxes, glazing, and backboards) to stabilize the panel; and control of
the environment in the room or display area by attention to heat sources
and local hot spots (such as fires and picture lights), drafts, and proximity
to windows, outside walls, and direct sunlight. While in many cases these
measures may be sufficient, some panels are so stressed or damaged that
complete removal of the cradle is essential.Cradle removal
Although this article does not propose to cover cradle removal in detail,
the following points should be considered: humidifying the panel before
cradle removal can reduce any sudden changes in curvature;^3 making a
bed that follows the panel’s curvature and irregularities and safely contains
the panel is vital;^4 and determining in advance the progression or direction
ofremoval is important, as it is possible inadvertently to increase the stress
locally while reducing it in another area.
The reaction of the panel to cradle removal may be discernible as
having several stages. The removal of the sliding battens can often trigger
an immediate increase in curvature. The removal of the glued members
down to a veneer thickness may not alter the curvature further. The
removal of the remaining veneer and animal glue can sometimes cause
thepanel to increase its curvature (Fig. 5a–f ), although it may occasionally
decrease the curvature.
After cradle removal, rejoining, and consolidation of any dam-
aged areas, the panel may be self-supporting, although fragile and
difficult to handle safely. In that case, an unattached auxiliary support
may be considered as an option to support and protect the panel while
allowing it movement.Size and thickness
In practice it has been found that panels larger than approximately 1 m 3
75 cm are not easy to accommodate using this system. Either they are of
such thickness that they do not require an unattached auxiliary support or
they are too thin, their strength-to-weight ratio being such that an attached
auxiliary support is required.
In addition, with a very thin, large panel, the weight alone can
trap the bottom edge and reduce the panel’s ability to move with changes
in humidity. This may lead to damage, even when Teflon PTFE is used to
line the frame/tray rabbet.Type of wood
There are great variations in the rate and amount of movement among
different types of wood, even aside from variations resulting from the cutSuitability ofa Panel for
an Unattached Auxiliary
Support374 Bobak