The Structural Conservation of Panel Paintings

should be of only a single plank free from sapwood. The text of Beurs

implicitly suggests that the use of other wood species would probably have

been experimental in nature.

This recommendation for using oak is in accordance with prac-

tice. However, exceptions are seen rather early in the seventeenth century:

sometimes walnut, pearwood, cedarwood, or Indian wood were used

instead. Mahogany was already in use by a number of painters during

thefirst decades of the seventeenth century and was used often in the

Netherlands in the nineteenth century. Even so, when canvas or copper

was not used, the main oeuvre of the northern school was painted on

oak panels.

The quality of an oak panel can be seen from its grain. If the medullary

rays in an oak panel are visible, the quality should be good, because this

shows that the plank was radially split or cut out of the tree trunk (Fig. 2).

The density of the wood is also important to the quality. Before 1630–40

the year rings (whose formation depends on age, physical location, and

climatological factors) are often found to be narrower than those of oak

trees available after this date.^5

In the sixteenth century sapwood is rarely seen on panels, but in

the seventeenth century a narrow edge of it is often recognized on one

side—in violation of guild rules that threatened a fine for the use ofsap-

wood (Van Der Straelen 1855). However, as panels inspected by the guild

keurmeesters(assay masters/inspectors) also show faults in the wood, this

may well be a consequence of the higher price of wood during the politi-

cally turbulent years in the beginning of the seventeenth century; or

perhaps there was such a high demand for panels that less control was

exercised over their production.

Quality ofWood

H O  P-M T   N C 151

König sberg

Elb in g

Marie nburg

STATE OF THE TEUTO NI C ORDE R

KINGDOMOF

POLAND Wars aw MAZOVIA

Cra cow

Dan zig

LIT HUANIA

BALTIC

SEA

Thorn

Figure 1
Vistula River basin with the main sources of
wood (marked by dots). Political borders are
those of the first half of the fifteenth century.