Unwrapping layers of history

New technologies can not only be used to detect forgeries but tell us stories about the people and methods behind original artefacts

Katana (sword) and Scabbard by Yokohama Sukenaya of Bizen, Japan, 1800 AD

Until relatively recently, it was impossible to know what was inside an Egyptian mummy without opening it. A couple of centuries ago, the unwrapping of a mummy could be a social event, a cross between drawing-room archaeology and pass-the-parcel. Amulets and other precious or semiprecious objects were excitedly examined as they were revealed by the unwound bandages.

Today, thanks to computer tomography scanning technology, which has advanced enormously even in the last 10 years or so, it is possible to unwrap mummies virtually and without damaging them in any way. In fact it is possible to examine and analyse their contents, both the cadaver itself and its adornments, with far greater accuracy than is available to the naked eye.

Ritual bronze wine vessel (Jue) from the Shang Dynasty 1600-104 BCE

The same technology is beginning to be applied to the charred papyrus scrolls of Herculaneum, which crumble to ash if physically opened. Contemporary CT scanning can read the traces of ink on the blackened pages, discriminating between layers of tightly rolled-up papyrus. This project could well lead to the recovery of lost classical texts of great significance.

But new forms of technological scanning can also be used, as this exhibition shows, to study objects whose provenance and even authenticity are unclear. This is particularly important for archaeological museums, which have to be alert both to looted artefacts and to forgeries. There is a lot of money to be made in forged antiquities, and despite the efforts of experts and scholars, there are undoubtedly a great many fakes, even in public collections.

For anyone interested in this subject, there is a fascinating and alarming documentary on YouTube from German broadcaster DW (look up Fakes in the artworld – the mystery conman), which reveals much about the forger’s art – in this case specifically ancient bronzes – as well as the means by which fakes find their way into seemingly respectable collections. Particularly striking is the willingness of many collectors to be deceived, blinded by the prospect of owning a newly rediscovered masterpiece.

Dating, of course, is fundamental to deciding on the authenticity of any suspect work. If it can be shown that a painting, for example, is executed on modern linen or uses pigments or paint formulations that were not available at the time it purports to have been made, it can be ruled out. Sophisticated forgers will try to use old materials wherever they can, as well as modern materials that are identical to those used centuries ago, although even these are no longer produced by quite the same processes, sometimes leaving traces that can be detected by modern technology.

Fragment of medallion, Ushak carpet, Turkey, 1600 AD

As the examples discussed above show, however, determining authenticity is not the only reason to use new technologies on old artefacts. It is still important to work out the date of an object even when its authenticity is not in doubt; it can be desirable to study objects in a non-invasive way; and there is much to be learned about how objects were made, what they are made of, if and how they have been repaired.

Many objects in this exhibition fit two or more of these criteria. One of the earliest is an ancient Chinese bronze libation vessel known as a Jue from the Shang dynasty and made about 3000 years ago. In this case, neutron imaging and proton-induced X-ray emission (PIXE) proved that this complex form – with long legs to stand in the hot coals and little knobs to allow it to be picked up with tongs – had been cast in a single piece, rather than in several that were subsequently joined together.

Another very early piece is a gold coin, with the facing heads of a lion and a bull on the obverse. This was the design of one of the earliest coins ever minted, under the legendary Lydian king Croesus, famed for his wealth and the subject of some of the most famous stories in Herodotus’s great history.

Figurine of Artemis from Greece, 200 BCE

When this coin was acquired by the museum, it was catalogued as a Lydian coin of the reign of Croesus. But the original Lydian coins were made of electrum, a natural alloy of gold and silver. Subsequent analysis of the alloy cast doubt on its authenticity, but now the most recent studies – using neutron imaging and neutron activation analysis – have confirmed that the coin is genuine, but because the alloy is mostly gold, it cannot be from the time of Croesus and must now be dated to the subsequent period of Cyrus, who conquered Lydia and continued to mint the lion and bull coins, but in gold rather than electrum.

There is a little marble sculpture of Artemis from the Hellenistic period, headless but readily identifiable as the divine huntress by her flowing robes, gathered up by a belt to allow her to move swiftly, and the quiver she carries on her back. Analysis of this statue reveals remains of paint but more surprisingly, traces of beeswax.

This seems hard to understand until we recall that Artemis had a special connection with bees, particularly in her cult at Ephesus on the Anatolian coast; the city’s coins even had bees as a civic emblem. Perhaps the wax is evidence of libations of honey poured over the statue; or could the small figure even have been placed among a cluster of beehives as a protective, apotropaic divinity to ensure the wellbeing of the bees?

Another beautiful little object is a Bodhisattva from Tibet in gilt bronze. In this case neutron imaging revealed part of a ceramic core inside the hollow bronze figure, confirming that the statue was produced by the lost-way method. This means that the figure was probably first roughly shaped in clay, then its surface finished in wax; then it was encased in more clay and baked to harden the clay mould, while melting out the wax layer. In the final step, molten bronze was poured in, replacing the wax surface with a skin of bronze, which still contained some remains of the original clay core, fired in the heating process.

In a different vein, there is a Turkish Ushak carpet from some 500 years ago. Carpets as old as this are rare, although many Anatolian rugs of this period are reproduced in close and documentary detail in European renaissance paintings – particularly clearly in the work of Flemish 15th century artists and Venetians influenced by them. They are frequently spread on the ground under the Virgin’s throne, but in private settings were often used as table coverings.

In the Persian-Turkish world, carpets were spread in mosques for the faithful to kneel on in prayer. When they became worn with use, new ones would be laid over the top of them, and in this way many very old carpets, and sometimes fragments of carpets, were in effect preserved under the layers that grew over the centuries. This carpet, rather oddly, has some parts missing altogether, while the parts that survive are surprisingly fresh in colour. Here technology has been put to a different use, digitally reconstructing the missing areas on the basis of the corresponding parts of the pattern in areas that remain intact, so that the screen on the wall behind the display can offer us a view of the carpet as it was originally woven.

Thus each of these objects, as well as illustrating the use of new technologies, is also a sample drawn from a particular culture and offering us many unexpected insights into the habits and thoughts of people of another time and place, like a geological core from which a wealth of information about the climate and natural environment from centuries past.

A set of samurai swords mounted in a case on the wall is particularly evocative in this way; they are katana, the longer of the two swords carried by a samurai. One is from the 14th century, one from the 17th and one around 1830, as can be confirmed from the swordsmiths’ signatures. The museum owned one other that was attributed on stylistic grounds to the 16th or 17th century, but not signed, and indeed had been fitted with a modern handle and given a modern scabbard.

The modern handle was less surprising than it may seem because many such classic weapons, possibly the best swords ever forged, were refitted in this way to be carried in World War II by Japanese officers. Neutron tomography, diffraction and residual stress analysis showed that the composition of this sword was consistent with the practice of the 17th century, so it was confirmed as an original of the best period.

The exhibition includes a couple of Aboriginal weapons: one is bone blade with a thick resin handle ornamented with seeds. Synchrotron X-ray tomography has shown that the blade is probably from cassowary bone, while radiocarbon analysis of the seeds suggests they were collected between 1877 and 1930.

The other piece is a boomerang that was found buried under 10m of mud in a bog; it must have been lost, perhaps while hunting waterfowl, and was thus unusually preserved, unlike all the other boomerangs of its time. Preliminary dating suggests it is between two and five hundred years old; if it were at the furthest end of this date range, it would be one of the oldest surviving examples of a boomerang.

New technologies can thus be used to measure the ­effects of time on artefacts and to detect the traces of the processes by which they were made and the materials of which they are constituted. But in one of the least conspicuous items in the exhibition we see the effect of human activity on a natural and living object.

After the war, the museum planted stands of eucalypts for study purposes, and a section cut from these trees a few years ago is displayed on a table. As it happens, the growth of the eucalypts coincided with the period of above-ground nuclear testing from 1945 onwards, before atmospheric, underwater and outer space testing were prohibited in the Partial Nuclear Test Ban (PNTB) of 1963, subsequent tests being conducted underground.

Growth rings mark the successive years of a tree’s life, and their variation reflects fluctuations in climatic and seasonal conditions. The resulting patterns of growth can be used, like the unique fingerprint of a particular time and place, to date a given piece of wood through a process called dendrochronology.

The above-ground nuclear tests, however, caused massive temporary rises in radioactive carbon in the ­atmosphere, and this of course had an effect on the rate of growth of the tree trunk. It is a sobering reminder of the impact of human activities on the natural environment; future dendrochronologists will be matching wooden artefacts of the later 20th century against a natural record of time distorted by the intervention of human violence..

The Invisible Revealed
Powerhouse Museum, Sydney, until May 22