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‘Dating and Wood’ by Professor Dr Peter Klein

Thu Mar 2, 2017

The 6 March 2017 marks the tenth anniversary of our exhibition Lost Faces: Identity and Discovery in Tudor Royal Portraiture. Guest curated by renowned art historian, David Starkey CBE, the exhibition included loans from Hever Castle, The Bodleian Library and The British Library (to name a few) as well as a number of our own discoveries.

The exhibition also allowed Philip Mould & Co. the opportunity share an insight into the forensic processes we undertake when a painting comes in to the gallery in ‘country house condition’. One of the most remarkable of these being dendrochronological analysis – the means by which we are able to date the wooden panels of sixteenth-century portraiture . Dr Peter Klein an eminent specialist of this field, who last week completed his 104th dendrochronological report for Philip Mould & Co., and generously contributed to our exhibition catalogue. The essay Dr Klein wrote in 2007 on this fascinating science can be found below…

Dating and Wood by Professor Dr Peter Klein, Seevetal, Germany

Dendrochronology is a method for dating wooden artifacts, such as panels supports. At present, oak, beech, fir and spruce can be dated, while linden and poplar cannot. Dendrochronology has proven to be particularly important for Netherlandish paintings above all for the fifteenth and sixteenth centuries, for, almost without exception, artists in the Netherlands used oak for their wooden supports, or panels, which was imported mostly from the Baltic region. Dendrochronological dating estimates can be accomplished in about 85 percent of panel pictures examined. The same is also true for English pictures of the period.

Oak trees lay down a growth ring each year of their lives. These annual rings can be seen on the flat surfaces of wood, but they are particularly visible as end grain on the top and bottom of the planks used to make up a panel. In dendrochronology, the distance between the growth rings is measured. The width of the ring differs according to the climate that year. The differences in ring width therefore allow us to see a pattern of growth that is unique to the climate and region where the tree grew. The growth pattern of the undated wood can then be compared with mater chronologies of wood of known age and location. A match results in a date for the annual ring that was the last year of growth found in the panel (often called the youngest year ring). This date can then provide a terminus post quem for a painting, since it allows an estimate of the earliest possible felling date of the tree and the wood’s subsequent use.

Certain variables have to be taken into account in order to arrive at dating estimates. When panelmakers prepared oak for panels, they usually trimmed off the bark and the light, perishable sapwood rings which must be added to make any circulation date. These depend not only on the age of the tree but also on the provenance of the wood. The growth of sapwood can vary in the western and eastern regions of Europe. For oak trees in the Baltic region, sapwood growth ranges between a minimum of 9 and a maximum of 36 rings, with a median value of 15. For Western Europe, the growth varies between 7 and 50 sapwood rings, with a median of 17. These values obviously apply only to the varying estimates of a tree’s felling date, and other steps are necessary to account for the number of years that might be involved in transport and seasoning of the wood. By referring to either signed and dated or securely datable works, it has been determined that panels of the sixteenth and seventeenth centuries were often used from two to eight years after the tree was felled. There are fewer dated works from the fifteenth century for comparison, but research suggests a period for transport and seasoning anywhere from ten to fifteen years but it is also dependent from the workshop and can vary. Dendrochronological analysis thus produces a series of dating estimates: the first possible date for the felling of the tree, the more probable date for the felling, and the earliest possible and more plausible date after which the panel could have been used.