which the panel may be kept in the future. Problems could also develop,
especially in the ground and paint layers, when unrestricted freedom of
response to environmental changes is allowed.
Sometimes the solution to the problems may be a compromise
dictated by display requirements. There is little point in designing a micro-
climate box or a 15 cm deep tray that cannot be accommodated in an orig-
inal frame or is unacceptable to the client for display purposes.
It is also worthwhile to consider a combination of ideas rather
than a single solution. For example, it should be possible either to reduce
or to slow down the response of a panel to environmental conditions with
a choice of barrier or buffering techniques, and then to combine the cho-
sen technique with a restraint or an auxiliary support. In addition, there is
now a wide availability of technology that makes environmental control
possible and more cost-effective in buildings where it would not have been
considered previously.
It is not easy to generalize or adopt a standard practice when
deciding which method to use. Every panel is different, and it would be
incorrect to expect that an acceptable answer to one particular problem
can be adopted as a principle for general use.
The fashionable answer among some nineteenth-century cradle
makers was to thin, flatten, and restrain panel paintings so that they could
be displayed like canvases. Today our views are different, and a lot oftime
is spent removing work that, when executed, was thought to follow the
correct approach but that can now be seen to be damaging. To avoid
falling into the same trap, today’s conservators should adopt an open-
minded approach and continually reappraise their methods and learn from
their own experience and that of others.It is the author’s belief that many conservators might remain isolated from
the benefits of an exchange of ideas if the opportunity to meet other spe-
cialist conservators were not made available. It is greatly appreciated that
institutions such as the Getty Conservation Institute continue to provide
these opportunities at an international level. The author would also like to
express his appreciation to the British Standards Institute (BSI) for his use
of material from a BSI publication.1 Reference tables of the modulus of elasticity for timbers including Sitka spruce appear in
Molesworth 1951:432–35.
2 Sitka spruce (Picea sitchensis), a softwood imported from Alaska and Russia, having consistent,
reliable mechanical properties. It is used for structural framework in some light-aircraft con-
struction (see Keen 1919).
3 Reference tables for modulus of elasticity from Molesworth (see n. 1) are given in lb in^22 ; they
have been converted into n mm^22 by multiplying by 0.0068947.
4 PVA Evo-Stik wood adhesive is generally the preferred choice for structural work. It is consid-
ered to have good long-term stability and flexibility, giving it higher shock resistance than ani-
mal glues, which may become brittle with age. Other adhesives used in these case studies were
rabbit-skin glue, for replacement of butterfly cleats, and an impact adhesive containing
toluene, for bonding Plastazote polyethylene foam to timber.Notes
Acknowledgments
400 Marchant