pointed out that in both directions of the wood grain, tensions in the
wood caused by these wooden blocks had the same deleterious effect. The
new, high-quality modern adhesives were to make reinforcement with
blocks unnecessary (Straub 1963:147). Nevertheless, the setting of small
wooden blocks is a reinforcing system that remains in use (Fig. 20). Fine
wooden veneer strips are also used instead of these wooden blocks.Repair of partially damaged supports
Repair of such damages to panels as cracks, holes, broken corners, and
edges has always been made with wood or filling materials. Cracks normally
are filled with wooden splints. Wormholes were filled with crushed paper
(Köster 1827:13) or with small sticks of oak wood (Welsch 1834:64). Holes
in the support could be filled with very old oak wood (Welsch 1834:64).
The gluing of wooden splints into holes is still in use today. This
type of reintegration of damaged parts of the support was in recent years
executed during the very difficult and delicate conservation and restora-
tion ofthe Grünewald painting at the back of the Lindenhart Altarpiece;
the conservation was conducted in the laboratories of the Bavarian Office
for the Care of Cultural Heritage (Bachmann 1978:7–19). It is still debated
whether it is beneficial to fill with the same wood as that of the original
support; some believe that the wood of reintegrated parts in the support
should be softer than the support, in which case balsa wood is convenient.
Many recipes exist for filling materials to be applied on the
wooden support. Köster worked with a traditional chalk or gesso ground
(Köster 1827:13). Welsch also preferred typical priming materials, such as
animal glue and chalk, or oily putty (Welsch 1834:64). Kainzbauer utilized
a mixture of sawdust, chalk, dextrin glue, and carbolic acid (Karbolsäure).
Wax-colophony mixtures also served as preferable filling compounds
(Brachert 1955b:30). Such compositions are well known in cabinetmakers’
traditions. In the early 1950s the first filling compounds bound with syn-
thetic resins became available. For example, polyvinyl acetate (PVA),226 Schiessl
Figure 20
Hans Baldung, Birth of Christ,1539. Reverse.
Oil on pinewood panel, 103 3 775 cm.
Kunsthalle Karlsruhe (inv. 90). The upper part
ofthe painting came into the collection as a
fragment in 1878; then in 1895 Friedläner
found another part. Both fragments were
combined in 1937, and the area where one
part is still lacking has been completed. The
photograph of the reverse from the late
1950s, before conservation, shows a reinforce-
ment of small faceted blocks, which were
removed in the subsequent conservation
treatment.