Dendrochronology is a method used to identify the formation time of growth rings in wood by measuring the distance between the rings. Good growing conditions produce wide growth rings, while poor growing conditions produce narrow rings. The pattern formed by tree rings of varying thickness is therefore typical for a certain period. The seasonal changes in our northern climate cause the very clear growth pattern typical for oak. In dendrochronology it is possible to determine the precise felling date of the tree down to the exact season of the year in which the tree was felled.
Such a precise dating however requires that the bark of the tree or the sapwood has been preserved. The sapwood lies just below the bark and includes the most recent annual ring formed in the wood. Unfortunately, in the production of panels for paintings the sapwood was often left out. Depending on the geographical origin of the wood, a prediction for the probable number of growth rings of sapwood which has been removed can be added to the existing rings, which then gives an approximate determination of the actual felling date, in addition to the earliest possible felling date.
By adding the many measurements into a computer program which already contains chronology curves for a specific geographical area, the tree can be dated very accurately. Chronology curves are created by examining both ancient archaeological timber and existing trees from a particular geographic area.
Dendrochronology can be used only on trees that form visible growth rings, for example oak. Tropical wood types such as poplar can not be dated by this method, since the more uniform tropical climate in the south does not produce clearly defined growth rings. Northern European painters of the 16th century mainly used oak as a painting support, while poplar was more widely used by painters south of the Alps. Dendrochronology is therefore far more common for dating paintings in northern Europe compared with southern Europe.
In the Netherlands, where there were lack of natural resources but great demands for art works, wood for panel painting supports was imported mainly from the Baltic region.
According to dendrochronological analysis the Tallinn panel is dated AD1560-1575 and consists of oak that probably originated in Poland.