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Portrait dendrochronology

by Angus Trumble, 26 August 2016

Mary, Queen of Scots by unknown artist, National Portrait Gallery of London
Mary, Queen of Scots by unknown artist, National Portrait Gallery of London
How do we make sense of the many unidentified, and, in many cases, surely unidentifiable Elizabethan and Jacobean family portraits that slumber peacefully in their hundreds, thousands, in the picture galleries and staircases of the Great Houses of Britain and have also migrated into public and private collections elsewhere? Until recently, there were two main problems to be solved: who was the sitter? And who was the painter?
Often, inscriptions purport to identify the sitter, and supply other useful information such as the date and the sitter’s name and age. On their face these details ought to be unimpeachable. However, increasingly accurate conservation analysis has proven that in many cases these inscriptions were drafted and inscribed long after the painting was finished, up to 150 years later, presumably at a time when memories were getting rather hazy, and there were concerns lest the identity of the sitter be entirely forgotten in fifty or a hundred years’ time—concerns that were amply justified. Often directed by a self-appointed custodian of dynastic memory, an authoritarian great-aunt perhaps, the agent, factor or librarian was set to work with an artist to add this helpful inscription, at times blissfully unaware that although the great aunt knew with powerful conviction that she was absolutely right, she was in fact wrong. This has given rise to much confusion between Lady Catherines, Lady Marys and Lady Elizabeths in adjacent generations, and other even more egregious errors.
The problem of “attribution,” meanwhile, identifying the hand of the artist, is complex. Such paintings are often caked with grime, at times fearfully damaged, and often inaccessible or shrouded in gloom in the farthest upper reaches of a picture gallery or staircase. As well, the subject of itinerant English provincial portrait painters and limners is still more or less in its infancy; the late Frances Yates and, more recently, Sir Roy Strong concentrated on “the greats,” e.g. Hilliard, Larkin, Peake, Gheeraerts, & Co. For the most part all we know about the second, third and lower ranks of sixteenth- and seventeenth-century English painters is that they were (a) populous, and (b) often made up of pupils with mixed abilities of mostly Dutch or Flemish painters, who were, in turn, usually based in London only for comparatively brief periods, depending, of course, upon peaks and troughs in demand at Court and/or the unreliable market for pictures that orbited the Court. What is changing everything, however, is the increasingly sophisticated study of dendrochronology.
Dendrochronology is the method of dating the demise of trees, and pieces of wood cut from them, by counting, measuring, and analysing the patterns formed by the rings that accumulate naturally through successive annual growth cycles in late spring, when wood grows faster and is less dense than in the autumn and winter, and may be clearly seen in cross section through the trunk, from its bark to its core. Evidence of such tree rings may also be observed and recorded along the edge of planks of wood sawn from individual trees, and although these necessarily tell only a relatively small part of the whole growth history of that larger tree, the unique sequence of seasonal variations that are preserved in such a piece of wood does nevertheless form a reasonably reliable fragment of a botanical fingerprint, as it were, that corresponds exactly with contemporaneous growth patterns in comparable pieces of wood from the same species of tree that once grew in the same region—an important caveat, because therefore such trees shared patterns of rainfall and other climatic conditions—unusually harsh winters or clusters of winters, or unusually warm long summers, for example, that dictated their rate of growth each successive calendar year. 
Until this was patiently explained to me by a whole roomful of colleagues at Yale some years ago, I could not be made to grasp how such ring patterns could provide anything other than relative data, with luck corresponding to otherwise independently verifiable dates that could, in turn, be pinned fairly reliably to particular pieces of wood. But let us suppose, for example, that one wishes to determine the exact age of a piece of oak that forms part of a fine English panel painting of approximately the late sixteenth century. This is how it is done: We now know that supplies of the finest quality close-grained oak were in the late sixteenth century imported to England from the Baltic region, and share certain basic characteristics. If you cut down an oak tree in that region today, right now, and analyse the ring patterns that radiate in reverse chronological order from the middle of the trunk you may trace how the rings correspond with each growth season extending from last year all the way back to the birth of the tree itself, perhaps 300 years ago. That sequence will necessarily overlap with the ring patterns in a piece of wood from a similar tree that was cut down 155 years ago, and was, let us say, at that date 420 years old. For 145 years both were growing at the same time and with the same annual spurts of growth, or enduring the ill effects of the same especially appalling winters, and this therefore yields reliable data that apply to annual seasons through an accumulated total of 575 years. How do we know the older tree was cut down 155 years ago? Because its last growth ring exactly corresponds with the 155th of the younger tree. By this method it is possible to assemble relatively accurate overlapping data, extending back for centuries, with which to compare the sequence of annual tree-ring growth patterns discernible in much smaller pieces of wood. This in turn allows the dendrochronologist to estimate within several years the exact date when each original tree was cut down. Isn’t that amazing?
There are a number of other variables, such as conventions of the Renaissance lumber trade that governed which portions of the tree trunk afforded the straightest and best quality planks, and the length of time such planks were left to season before sale in batches, which usually means that the age of the plank is significantly less than the date when the tree was felled, but greater by a certain number of years, perhaps up to seven, than the age of the panel painting the plank was used to fabricate. Occasionally, other evidence contained within the painting itself may be used to narrow down the available date range afforded by the dendrochronologist, and other documentation about extremes of climate may also help to confirm data that is occasionally otherwise compromised by the action of wood-eating insects, etc. However, we do know that by this method it has been possible to identify certain English panel paintings that were definitely made from planks hewn from the very same tree, and, in some astounding instances, hewn from the very same plank! This does not necessarily shed any more light upon our painting than that the craftsmen who supplied the artist with his panel sourced their timber from a single batch—occasionally identifiable with crude batch marks that, incredibly, are beginning to be accumulated. That batch may or may not have kept an artist’s workshop supplied with the raw material to make their panels over an additional period of months or even years. Still, it is amazing, because by this method it may be argued that our late sixteenth-century English painting adheres to a panel made from Baltic oak that was felled in 1585, which is what we like to call a reliable terminus post quem. One must be wary, of course, because cunning forgers have at times been easily capable of using an old panel to fabricate a new picture, and pass it off as something else entirely, but that is a very different story.
Anyhow, as time goes on the dendrochronological data set will surely, gradually, steadily improve, and open up a hugely fruitful vista with which to make sense of sixteenth- and seventeenth-century English portraits—and link individual pictures scattered over different family collections to a single itinerant workshop in which various craftsmen collaborated in different ways, and the painter or painters were merely engaged upon the final part of a very complex process of manufacturing of which until recently we were barely even aware. That vista, of course, has in many respects redefined our understanding of what a workshop style in Elizabethan Britain actually meant, and is beginning to replace what recent generations came to regard as a signature hand or style to be identified with a single artistic personality à la Sir Joshua Reynolds—a concept with which we are obviously still living today. In other words, in these early cases, the question “who was the artist?” may be the wrong question, while the question “who was the sitter?” may never be answerable.
By and large sixteenth- and seventeenth-century British art collectors, historians and connoisseurs were no less sophisticated than we are today. In some respects they were considerably more deft in their judgments than we are in ours. So the really fascinating question for a National Portrait Gallery to consider is this: What questions will be asked about the objects in our care 300 and 400 years hence that are, by our lights, simply the wrong questions, or else questions that through no fault of future generations will probably not be answerable for the simple reason that we cannot even conceive of what they will be.
In the midst of a busy working life I find this keeps things nicely in perspective.
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