But splitting was still recommended when a damaged support required a
partial transfer. In such instances, it was noted that the separated back side
should always be preserved (particularly if there were inscriptions, seals,
and marks) and that after the transfer of the painting with its split, thinned
support to a new rigid support, this original back side should be glued onto
the reverse of the new support (Goldkuhle 1932:15).
Finally, splitting of double-sided panel paintings has been done for
conservation reasons. Thomas Brachert discussed the method again in 1955
(Brachert 1955b). He pointed out that splitting a double-sided panel painting
spells the destruction of an original, organic work of art, although it can
sometimes be the indicated treatment when blistering panel paintings can-
not otherwise be preserved. There are occasional examples of this. In 1957
Schmidt-Thomsen published a well-documented case study about the partial
transfer of a double-sided panel painting (Fig. 10a–f ) (Schmidt-Thomsen
1957:6–11), and an unpublished treatment was executed by the conservator-
restorer Adolf Jobst in 1969 at the Hessisches Landesmuseum in Darmstadt.Thinning of the support
Split double-sided panel paintings were sometimes left without any other
treatment on the newly exposed surface, so that the saw marks remained
visible (Fig. 11). But frequently, auxiliary supports or auxiliary construc-
tions such as cradle systems were added to the rev erses, and then the sawn
surfaces were treated to obtain an even surface or smooth thickness. To
accomplish this, the saw marks and the drifts of sawing were usually
smoothed with a tooth plane or smooth plane. If the thinning and planing
were done well, it may be impossible—except for the extant corresponding
side of the painting—to determine if the painting had been double-sided
and was split or if it had originally been one-sided. Through such treat-
ment, even the supports of some larger-sized paintings have been thinned
to 2–5 mm thick.
In southern Germany, Austria, and parts of Switzerland, supports
were mostly of coniferous wood, but oak supports were also thinned to
a minimum of 2 mm (Zehnder 1990:passim; Goldberg and Scheffler
1971:passim). Italian wooden panel paintings, consisting mostly of poplar,
were also thinned to 0.5–1.2 cm (Boskovits 1988:18–19, 27, 85, 136–37).
The sawn surfaces often retain evidence of dowel holes.
In general, all panels required cradle and auxiliary supports
after thinning. It is easier to flatten very thin panels than thick ones. The
reverses ofone-sided panel paintings have also been thinned by planing
to expose the tunnels of burrowing wood insects for better impregnation
treatment. Thus, not only split panels but also numerous (originally)
one-sided paintings appear today with only a small portion of their
original support.Pest control
Many methods have been used to attack insects and fungi in wood, espe-
cially in painted panel supports. Solutions of salts were used for impregna-
tion (Schiessl 1984:10–11). Treatments against insects were used against
fungi in anticipation of good results, but to no avail. The opposite approach,
using known fungicides as insecticides, was also unsuccessful. Mercury
chloride was often used in the eighteenth century and recommended inH P P C A, G, S 209