Facing of the surface before structural consolidation work
Panels once consolidated on the surface are usually faced before any other
treatment is carried out. Crack or join repairs are usually faced up to their
edges. The facing should cover the surface entirely if structural or removal
work is to be carried out on the back. The rationale for choosing a particu-
lar facing material and facing mixture depends on the surface, solubility,
and condition of the painted layer and also on the structural work to be
carried out. The materials commonly used include Eltoline tissue with
Paraloid B72 or B67, or damar with a little wax. Occasionally, aqueous fac-
ing adhesives are used, but usually only for transfer treatment. If more
than one facing has been applied and it is necessary to release or remove
one or more of the facings, then the later layers should have different
adhesives to ensure that the picture will always be protected. Where there
are open cracks to treat, and protection is necessary, B72 or B67 is nor-
mally used first.Removal of old nails or fixings and the treatment of
cracks and joinsIf normal methods of removing old nails or fixings are not adequate, heating
the metal (which causes expansion and the ensuing contraction) may help.
Having used traditional clamping tools and experienced their limi-
tations, the author designed a clamping table, which was manufactured by
Willards of Chichester (Reeve 1990) (Fig. 2).^1
The adhesive generally chosen for joining cracks is Cascamite, a
powdered urea-diformaldehyde synthetic resin with a hardener. Its advan-
tages are that it produces bonds that perform well when exposed to
extreme dryness or dampness, or even when completely saturated in
water. The aqueous quality of Cascamite allows softening and slight
expansion of the edges of wood being joined. It also has the possibility of
being used in dilute form for penetrating small closed cracks, or in thickerS C P P N G, L 405Figure 2
Clamping table for panel conservation.