One of two original rectangular beech wood (Fagus sylvaticaL.)
inserts, visible on the front, had been exposed in an empty mortise at the
back (Fig. 10a, b). The insert had been used to replace a wood defect. The
adhesive did not appear to be casein, as was used to join the planks, but
animal glue.^28 Where visible within the larger gaps, the joint faces had
been inscribed with shallow Xs, either for adhesive tooth (which seems
unlikely) or perhaps to ensure adequate glue pickup from the brush.
From the evidence then, the procedure for joining was as follows:
the joint surfaces were planed; regular Xs were carefully inscribed into
each surface and mortises were chiseled; one end of each tenon was glued
with casein into one of the mortises of one plank;^29 the same glue was
applied to both joint surfaces and to the protruding tenons; the planks
were pressed firmly together and possibly rub-joined,^30 since the glue lines
are relatively thin and do not appear to have dried in a “starved” condition.
After drying, the desired height dimension was achieved, and the edges
were squared with narrower strips, nailed and glued to top and bottom
edges. The sides were trimmed square and straight.
Similarly, the Palmezzano would have been about twice its current
thickness. Again, as with the Mengs’s tenons, poplar dowels were used
to maintain rough alignment during assembly, and then the edges were
finished. Thinning had exposed some dowels. Also similarly, long spikes
remained that would have been driven straight, and with evident skill,
nearthe original midline of the side edges.Insect damage
Larger panels have proportionally greater expanses of insect-prone wood.
Practical construction from whole planks would have favored greater
plank widths. For economy and practicality, critical edges of sapwood were
sometimes left in longer planks, partly because the transition line between
heartwood and sapwood is irregular for some types of wood used for pan-
els, such as the walnut and poplar used here.
Nearly every plank of the Palmezzano had variable, discontinuous
lengths of damaged sapwood.^31 In more central, critical areas, the damagedP A S C L P P 459Figure 10a, b
Anton Raphael Mengs, Noli Me Tangere. On
the back, an original beechwood insert (a) in
the walnut panel can be seen through an
exposed mortise. The same insert viewed
from the front (b) before treatment and in
top-raking light.
ab