however, it is not a practical method except in the most unusual circum-
stances. Parallel samples were used to extract the wood only, to determine
theamount of extractives that would presumably be removed along with
the consolidant. Before and after each procedure, specimens were condi-
tioned to constant moisture content in a controlled-environment room.
Table 4 shows residual resin content as the difference between
original weight and weight after extraction, with correction for extractive
removal considered both before and after. Negative values before correc-
tion occur if the true residual resin is less than the amount of extractives
removed. Only one corrected value is negative, a result that may be due to
imperfect matching with the samples for extractive-content determination.
The data show that acetone and methanol were more effective generally in
extracting consolidant than toluene or the ethanol-toluene mixture, and
that AYAT and Acryloid B72 treatments were more reversible than the B98
treatment. The use of agitation was very effective, and for Acryloid B72
and acetone, it achieved results as good as, if not slightly better than, the
results of the soxhlet extraction. The AYAT treatment in acetone proved
the most reversible (Schniewind 1988). Thus, there is ample evidence that
soluble resin consolidants can largely be extracted again, but that small
amounts of resin are likely to remain.In the discussion thus far, it has been assumed that the consolidant used
should not come into contact with either the paint or the ground layers.
This constraint represents a severe limitation of accessibility for consolida-
tion of a painted panel as compared to an unpainted wooden artifact, and
this limitation would also make it practically impossible to treat a wooden
panel that has a painted image on the rev erse. Furthermore, soaking by
total immersion or vacuum impregnation would not be possible unless an
effective, temporary barrier could be created to isolate the paint layers
from the consolidant. Still, consolidation ofpolychrome wooden artifacts
by vacuum impregnation, particularly with monomers polymerized in
situ, is not unknown, and some examples have been described by Schaffer
(1974). For instance, methyl methacrylate monomer is quite volatile, and if
care is taken, the monomer will evaporate from the surface layers before
polymerization can take place, thus preventing the formation of any sur-
face films. It may also be helpful if a temporary barrier coating can be
applied to prevent potential problems. While such a total impregnation
procedure should not be rejected outright, it must nevertheless be
approached with the utmost caution.
The nature of the deterioration needs to be considered when the
consolidation ofwooden panels is approached. Deterioration rarely pro-
ceeds in a uniform fashion, so it is entirely possible that impregnation will
be required only in localized areas. For example, fungal decay may well
occur in scattered pockets. If deterioration was caused by insect attack,
the nature of the boreholes (i.e., small or large, isolated or coalescent,
clean or filled with frass) is an aspect that could have a bearing on treat-
ment choices. In cases where there are large areas of loss, fillers f or the
larger voids may need to be considered. Wermuth advanced the concept
of primary, secondary, and even tertiary consolidants in such a context
(Wermuth 1990). There is no reason that this distinction could not apply
to panel paintings in particular cases.Treatment of
Wooden Panels102 Schniewind