Pest fumigation of wood has also gone through fundamental
changes. Having been practiced since antiquity, fumigation may be one of
the oldest methods of impregnation of wood (Unger 1988). In the eigh-
teenth century sulfur dioxide was used for fumigation. Prussic acid, first
used around 1880, is no longer used. Today new experiments with nitro-
gen and carbonic acid have shown promising results.Consolidation of panels damaged by insects and fungi
Until the 1950s the diagnosis of extensive damage by insects or fungi on a
wooden panel painting support always led to drastic treatment measures:
total or partial transfer of the support. Less pronounced damage provoked
responses that would be considered aggressive today. One such “light”
operation was planing the whole reverse to open the burrowing passages
of wood insects to enable better impregnation.
Exhaustive studies about wood consolidation and especially about
wooden painting supports have been written in the German language;
only a few are mentioned here. R. E. Straub wrote the first systematic
critical introduction to both pest control and wood consolidation (Straub
1963:128–40). The general study published by Brigitte Aberle and Manfred
Koller in 1966 on wooden sculptures is also valuable for panels (Aberle and
Koller 1966). Achim Unger’s important book about wood conservation
contains a very complete bibliogr aphy, material descriptions, and recipes
used for treatment materials (Unger 1988).
There is insufficient room in this article to describe all the materi-
als used for wood consolidation during the history of conservation. Today
scientific identification of old consolidation materials remaining in the
objects and the study ofthe degradation of such materials has become a
new, highly problematic topic in conservation research. Thus, exploring
old restoration texts may be of value. In 1834 Welsch recommended an
impregnation mixture of copal varnish, turpentine oil, and boiled linseed
oil (Welsch 1834:65). An early method for the consolidatation of degraded
wood was impregnation with animal glue mixed with alum as a hardener.
Amixture of casein glue and alum is also mentioned (Wolters 1952).
Attempts to reinforce wood include the application of shellac, followed
bya putty of hardwood sawdust, chalk, dextrin, and carbolic acid
(Kainzbauer 1922:38).
The advice to remove all of the wood possible, however, as well as
to cradle, appeared frequently in early literature (Lucanus 1832:77). In some
instances, wooden supports have been so weakened by degradation that
they have required consolidation before they could be thinned with a plane.
The Wolters Report of 1952 provided a good overview of the con-
solidation materials used for panel paintings until the 1950s. It noted dis-
cussions both for and against cellulosic acetate and cellulosic nitrate.
Some laboratories preferred solutions of natural resins such as colophony
in turpentine oil, shellac in alcohol, and mixtures ofwax-resin solutions.
Compositions of resin, wax, and linseed oil or Chinese wood oil, and
casein glue with alum were also described. All restorers interviewed for
this report rejected bone glue and hide glue. The use of combined con-
servation materials for the dual purposes of pest management and wood
reinforcement was remarkable (Wolters 1952).
In the 1960s Straub described a preference for consolidation mate-
rials that hardened without solvent action (e.g., some types ofwax, mix-212 Schiessl