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Tests on Canterbury Cathedral’s stained glass find links with ancient Egypt and Imperial Rome

02 August 2021

Courtesy of The Chapter, Canterbury Cathedral 

The great south window: David and Nathan are highlighted. See gallery for more images

The great south window: David and Nathan are highlighted. See gallery for more images

SCIENTISTS have “discovered” Britain’s oldest large-scale stained-glass works of art in Canterbury Cathedral.

Their tests reveal that stained-glass figures portraying four ancestors of Christ were made for a rebuild of the eastern half of the cathedral in the early-to-mid-12th century. The discovery is allowing art historians to reconstruct theoretically, for the first time, an important aspect of the internal decor of the Norman cathedral, England’s most important ecclesiastical building.

Before the scientific tests, experts had no way of determining the age of the figures. All that was known for sure was that they had been created in or before the early 13th century. Now their true age has been revealed.

The new scientific and historical research also tells a story involving aspects of ancient Egypt, Imperial Rome, and English Puritan iconoclasm.

Although the stained-glass figures were created in the first half of the 12th century (perhaps in or around 1130), tests on other ecclesiastical stained glass from England and France suggest that parts of the Canterbury figures were made of re-melted ancient Roman glass, manufactured about 1000 years earlier.

Six different colours — red, pink, purple, yellow, green, and blue — are featured in the newly identified Norman glass. The tests reveal, however, that the blue pigment is cobalt: a mineral for which, in the 12th century, no natural sources were known to European glass-makers.

They (or their suppliers) had, therefore, almost certainly obtained their cobalt by melting down thousands of Roman blue-cobalt-coloured glass cubes used in Roman wall mosaics, many of them located in Italy.

The cobalt found in the newly dated glass almost certainly derived originally, in Roman times, from currently unidentified mines in the Balkans or the Middle East. The Canterbury glass probably also contains a crucial component from ancient Egypt.

Evidence from tests carried out on blue cobalt stained glass from medieval church windows elsewhere strongly suggests that the flux (the glass-melting additive) used by the Romans to make the original glass, ultimately re-used in Canterbury, was soda (sodium carbonate).

The soda with which the Romans made their cobalt-blue glass mosaic cubes was obtained from salt lakes in the Wadi el Natrun area of northern Egypt. Soda had originally been extracted from those lakes and salt flats because the ancient Egyptians needed it to mummify their dead.

The four newly dated figures portray four of the traditional Old Testament ancestors of Christ; but it is regarded as almost certain that they originally formed part of a series of about 40 around the interior of the east end of the cathedral, in more or less every window in the upper part of that portion of the building. Most of the original Norman-period figures were, it is thought, destroyed in a fire in 1174.

After the fire, the four surviving Norman-made ancestor figures — King David, Prince Nathan (King Solomon’s brother), King Rehoboam (Solomon’s son), and King Abijah (Solomon’s grandson) — were relocated to new windows created in the early 13th century.

Historical evidence shows that they stayed there until the very late 18th century, when the four were split up: two figures were inserted into the cathedral’s great south window, and two into its great west window. Space there had been created by Puritan iconoclastic activity during the English Civil War.

“It’s extraordinary that Canterbury’s newly redated first-half-of-the-12th-century stained glass has survived through the centuries,” Professor Tim Ayers, of the University of York, an expert on medieval stained glass, said.

Canterbury Cathedral’s senior stained-glass conservator, Leonie Seliger, said: “The 12th-century masterpieces had, in a sense, been hiding in plain sight.”

The redating was made possible by a new portable testing method, developed at University College London by an archaeological scientist, Dr Laura Adlington.

Professor Ian Freestone, a UCL archaeological scientist involved in the Canterbury project, said: “The technology is particularly exciting because it demonstrates how science is contributing to solving historical and art-historical questions.”

The redating makes these figures the world’s earliest known stained-glass masterpieces portraying a series of the Old Testament ancestors.

After the 1174 fire, the other figures were recreated in a later style and increased in number during the rebuilding of the cathedral. Thirty-one of these recreations survive. Together with the four surviving earlier figures, they are by far the largest series of medieval portrayals of Christ’s traditional ancestors anywhere in the world.

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