The Structural Conservation of Panel Paintings

second curve by maximum coincidence leads to absolute dating. For each

kind of wood, a master chronology must be established for different geo-

gr aphical regions.

In the course of dendrochronological work, a number of problems involv-

ing the biological material and the methodology are encountered:

1. Conifers (such as spruce) or diffuse-porous broad-leaved trees
   (such as lime) may not even produce a ring in some years, thus
   preventing accurate dating because of the missing data.


2. Sometimes the state of conservation of a sample does not per-
   mit determination of the ring widths, as in the case of sap-
   wood that collapses from excessive drying or that is destroyed
   by insects, bacteria, or fungi. In some cases, not even the num-
   ber of rings can be determined.


3. For the cross dating of curves, one needs a minimum number
   of rings to obtain reliable results. Unfortunately, it is not pos-
   sible to give a definite figure as the minimum. Even curves
   considered quite “long” sometimes do not provide the charac-
   teristic pattern necessary to date the curve. There are so many
   variables that sometimes dating is possible with as few as 50

Problems

42 Klein

Lübeck Gdansk

Amsterdam

Antwerp

Calais

London

Figure 3
Areas of the natural distribution of oak. The
distribution ofQuercus robur L. (European
oak) is shown as a heavy line; the distribution
ofQuercus petraea Liebl. (sessile oak) is shown
as a broken line. European oak originates
farther northeast than does sessile oak. The
sources of oak timbers and the places of their
use as panels are indicated by arrows.