Atomic bombs date fake drams
25 January 2009, by Tom Marshall
Spotting fake scotch may not seem natural territory for a scientific archaeology facility specialising in putting dates on material from thousands of years ago.
But the Oxford Radiocarbon Accelerator Unit, which is part-funded by the Natural Environment Research Council (NERC), has developed a thriving sideline sorting the sheep from the goats among single malts.
Trade in antique whisky has boomed in recent years, with bottles reputedly dating back to the nineteenth century changing hands for thousands or even tens of thousands of pounds at auction.
As with any scarce and valuable product, forgers have appeared, trying to pass off disguised bottles of modern whisky as valuable antiques. Several high-profile sales have been overshadowed by controversy, and auction houses and whisky collectors have turned to science for the answers.
'So far there have probably been more fakes among the samples we've tested than real examples of old whisky', says Dr Tom Higham, deputy director of the unit.
Radiocarbon dating works by measuring the presence of a certain variety of radioactive carbon. It works on organic material like leather or wood; plants take in radiocarbon while they're alive, depending on how much is in the atmosphere at the time.
'So far there have probably been more fakes than real old whiskies.'
Dr Tom Higham
This radiocarbon makes its way up the food chain into animals. After death, an organism's radiocarbon content decays at a steady rate, letting scientists put a date on when it died.
The method can be applied to whisky, which is made from barley and hence has a radiocarbon signature - although the information that can be gleaned about something as recent as old whisky is limited.
The lab is sent a small phial of whisky, which is then burnt and the results purified before the radiocarbon can be measured. For the period between 1700 and 1950, the result comes as a range of possible dates. The lab usually can't put a firm date on, say, when exactly in the 19th century a whisky was made. But they can very easily tell if it comes from before or after 1950.
That's because around this time, traces of radioactive carbon from early atomic bomb testing started to appear across the planet. All organic material from after the 1950s has a distinctive radiocarbon signature.
'We can often only really tell if something is post-1950,' says Higham. 'If a sample comes from after 1950 we can often put quite a precise date on it. If it's from before then we may only be able to say that it doesn't contain bomb carbon.'
Most of the lab's work in this area has come from the Scotch Whisky Research Institute (SWRI), which sends small samples of the whisky it wants tested. Before starting on real dating problems, the SWRI sent a variety of whiskies whose date it already knew for certain. The Oxford lab dated most of these successfully, using the results to calibrate its subsequent results.
'We got them all right, except for one case where we found bomb carbon present but the sender said the whisky was made before 1950,' says Higham. 'We repeated the tests and got the same results. Eventually it turned out that someone there had accidentally sent us the wrong sample!'
One case involved a bottle of Bowmore whisky, which sold for almost £30,000 to a private Russian collector in 2004. The auction house claimed it dated from somewhere between 1850 and 1880, and sought confirmation from radiocarbon dating.
Unfortunately, experts at the auction house initially misinterpreted the lab's results, incorrectly believing they meant the whisky had to date from some point in the first half of the nineteenth century. In fact, the date range provided was much broader, and suggested only that it was produced some time between the early seventeenth and early twentieth centuries.
Another success for radiocarbon dating was a bottle of Macallan Rare Reserve, which had to be withdrawn from auction at Christie's when it was found to have been produced after 1950 despite being claimed to date from 1856.
The lab has also made a foray into wine dating, confirming during the 1980s that a cache of Chateau Lafite that was found underground in Paris could indeed have belonged to Thomas Jefferson, as experts believed. At the time of its auction, this was the most expensive bottle of wine ever sold.
Higham explains that wine is trickier to date than whisky as it has a greater range of organic compounds that can obscure its true age.
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