The shellac method for flattening wooden panel paintings may be
beneficial in that, unlike other systems, it does not require pressure. The
method aims to make corrections of warping only as far as it is allowed by
the condition of the individual support.Pressure for flattening
Lucanus and Welsch were the first to write about the application ofpres-
sure. The warped panel painting may be positioned on small wooden slats
and covered with a cloth. Then, after every moistening, the load on the
top of the panel is made increasingly heavy (Lucanus 1832:116; Welsch
1834:62). The Austrian Ludwig Kainzbauer recommended an even easier
straightening method—laying a moistened panel (painted side up) on the
floorand toploading it (Kainzbauer 1922:36). Although in the German lit-
erature there is little technical information about the application of pres-
sure to panels, there is one good example from Secco-Suardo (Zillich
1991:40–45). All tools of the joiner, such as screw clamps, were used to
set pressure to flatten. Most of the panels, however, may have been
thinned and cradled, or glued to an auxiliary support. Later case studies
onflattening and cradling mention the affixing of screw clamps after
flattening and up to the moment of cradling (Wehlte 1958:106).
Drying under tension was another method to flatten panels.
Smalland thin panels were first moistened and flattened by swelling of
thereverse. They were then immediately nailed into their frames to keep
them straight (Welsch 1834:63; Kainzbauer 1922:36). According to the
Wolters Report, one conservation laboratory applied slight pressure on the
panels, working with a veneer press and many cauls of wood and rubber
(Wolters 1952:10).Slots and wedges
Another practice was cutting along the grain in the reverse of a warped
panel to facilitate effective penetration of water into the wood structure.
Water was dripped into the cuttings and slots. When the painting was flat,
it remained under pressure. These slots were then filled. After drying and
hardening, pressure was removed from the panel. The fillers kept the panelH P P C A, G, S 215Figure 12
Frankonian master, Epitaph for the Nun
Gerhäuser,1443. Reverse. Tempera on panel,
114 3875 3 2.2 cm thick. Bayerisches
Nationalmuseum (inv. MA 2586), Munich.
The painting was treated in 1960–61 with the
shellac method to flatten it. This photograph
ofthe reverse, from 1994, before conserva-
tion, shows a rigid cross slat that contributed
to the enormous crack in the middle of the
support. The thick and glossy shellac layer is
remarkable.