EDINBURGH - A large number of rare and collectable whiskies, sometimes sold for hundreds of thousand of pounds, are likely to be fake, researchers have found.

Investigators from the Scottish Universities Environmental Research Centre used carbon-dating to sample 55 bottles of Scotch bought through the secondary market, discovering that 21 were outright fakes or not distilled in the year declared, Rare Whisky 101, which commissioned the study, said.

The sale of rare collectors' whiskies is more and more popular, and this October a 60-year-old The Macallan Valerio Adami 1926 was sold for record 848,750 pounds ($1.08 million) at auction.

Researchers look at minute levels of radiocarbon absorbed by the barley used to make Scotland's flagship export to determine its age. Those with higher levels of radiocarbon must have been distilled prior to the 1950s nuclear era, they said.

The accuracy of the process is such that they can pinpoint likely distillation years to within a two to three-year period after the 1950s, and a wider period before.

"It is our genuine belief that every purported pre-1900 - and in many cases much later - bottle should be assumed fake until proven genuine, certainly if the bottle claims to be a single malt Scotch whisky," said David Robertson, co-founder of Rare Whisky 101, which publishes insight and intelligence for whisky collectors.

"This problem will only grow as prices for rare bottles continue to increase," he added. 

Reuters