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How Does Dendrochronology Work?

Dendrochronology is a method of using tree-ring patterns to date wood.

Dendrochronologists look at the pattern of wide and narrow growth rings in a piece of wood and compare these rings to weather patterns in different regions over time.

Wide rings grow in wet years, narrow rings in dry years. Scientists can date a piece of wood by comparing its tree-ring patterns to the tree-ring patterns of other pieces of wood felled in different places and times.

Measuring the Rings
Scientists examined the ring patterns in 17 pieces of the cabinet's structural panels, which are made of oak.

Photographing one of the cabinet's oak panels
Photographer Jack Ross takes high magnification photos of one of the cabinet's oak panels Enlarge

Where the end grain of the panels was visible, they took high magnification photographs. Where the end grain was not visible, they made high-resolution X-rays.

Average growth chronology

Average growth chronology for the Getty cabinet Enlarge

Dendrochronologist Didier Pousset used the photographs and X-rays to create an average growth chronology (left) of the oak in the cabinet. An average growth chronology is like the fingerprint of a tree.

Pousset then compared the fingerprint to several master chronologies, records of woods whose ages and origins are known.

Each master chronology is created by aligning the tree-ring series of living trees and the tree-ring series of documented architectural timbers, such as from well-known buildings. By overlapping the rings of increasingly older wood, a virtual "endless tree" can be constructed that extends far into the past (see diagram).

What We Learned
The analysis revealed that the oak used to make the cabinet came from a tree that was cut down in the autumn or winter of 1574–75 in the region of Burgundy, France.

Since the wood would have had to dry (or season) for several years and the construction of the cabinet would have taken some time, this analysis strongly supports the date of 1580 painted on the cabinet.

Master chronology

A master chronology is created by lining up a series of pieces of wood Enlarge
The J. Paul Getty Trust
The J. Paul Getty Trust