Dating the panels
Walker Art Gallery's Henry VIII before conservation
The investigation of the four Henry VIII paintings also included an analysis of the wood panels they were executed on using a technique called dendrochronology, or tree-ring dating.
This involves dating wood by measuring the thickness of the growth rings across the grain of the sequence of ring widths. The sequence of ring widths is then compared with wood samples of known dates for particular species and geographical area. All four of the portraits in the exhibition (from Walker Art Gallery, Petworth, Chatsworth and Trinity College) were painted on oak from the Baltic region of Northern Europe.
Walker Art Gallery's Henry VIII after cleaning
The tree-ring analysis for the Baltic oak panels that Walker Art Gallery's Henry VIII was painted on revealed that it was felled after 1530. It is possible, although not certain, that the painting could have been created in Henry's lifetime - he died in 1547.
However it is important to understand that an accurate date for the earliest calculated felling of a tree can only be established when the samples are complete with sapwood or bark-edge. Where none exists, as is often the case for a painting, only the date after which the tree must have been felled can be determined. The date of the felling must not be confused with the date of the use of the timber - it may have been in storage for some time, or transportation of the wood may have taken some months.
The date for the Petworth portrait was also early, after 1525, while both the Trinity and Chatsworth portraits had later felling dates - after 1554 and after 1557.