Dating Cognac (August 19, 2010)
From time to time I get emails that read something like "I found this old bottle in the attic and I was wondering what it's worth today."
Usually it's a wine that is so far over the hill that it needs a passport to get home. Or a forgotten bottle of Canadian wine from a winery that has long ceased to exist and doesn't deserve house room.
But recently I was approached to authenticate and evaluate a bottle that purported to be an ancient cognac. Apparently, it had been in "grandmother's closet for 70 years."
The hand-blown, brown Rheingau-style bottle had a slightly stained label declaring it to be a vintage 1874 Fine Champagne Cognac, bottled by Bourgogne & Co in Newcastle-on-Tyne. (The company is no longer in business. Fine Champagne, incidentally, is a blend of Grande Champagne and Petite Champagne – the two best zones in the Cognac region.) That was all the information I had to work with. The level of ullage was about two inches below the level of the cork, consistent with an old brandy.
The problem was the cork. There was no seal over the top and it looked as if the bottle had been opened and recorked. The new cork was very short with an uneven surface, which suggested that someone may have pulled the original cork, sampled the cognac and used another cork to stopper it. There is no possible way of telling if this cognac was authentic without tasting it and subjecting it to laboratory analysis. Since the integrity of the cork had already been compromised, I had the owner's permission to open the bottle, taste it and run any analyses necessary.
If the cognac was truly a vintage 1874, it could be worth $1500. But no collector would purchase it without a certification of authenticity at that price.
I contacted the LCBO Quality Assurance lab, and its vice president George Soleas kindly offered to test the cognac with me. The first step was a sensory evaluation: we decided to taste test the product against three other aged cognacs – Prunier Très Vieilles Grand Champagne Reserve, Hine Triomphe Grand Champagne and Brillet Cognac Hors d'Age Grand Champagne. The 25 mL samples we poured showed that the "1874" was dramatically darker in colour than the other three, whose ages ranged from 30 to 50 years old. It was brown-black in colour with an olive green rim while the others ranged from coppery-amber to deep bronze. The nose of the "1874" had that rancio note of old sherry, mixed with woody, spirity notes. This would be consistent both in colour and bouquet for a cognac that had been kept in oak barrels for a long time. (Most cognac houses will take their eaux-de-vie out of cask when it reaches the age of fifty and keep it in glass carboys in their "Paradis.")
On the palate, the "1874" showed definite drying out but still had that great length and exciting fiery quality.
It certainly tasted like a venerable old cognac, but the question remained: had it been topped up with younger cognacs? To determine this, the LCBO technicians put the four samples (what remained from our tasting) through a battery of tests. Using high-performance liquid chromatography and gas chromatography isotope ratio mass spectrometry, they could determine, by extrapolating the isotope ratio of carbon-12 and carbon-13 atoms, the relative ages of the four cognacs. The isotopic ratio of the "1874" proved to be significantly different from the three younger cognacs, which were relatively the same. Nor was there any evidence of dilution by topping up the old bottle with a younger cognac. If this had occurred, the carbon ratio would have been closer to that of the three control cognacs. So, while there was no definitive determination that the old bottle was indeed of the vintage
stated on its label, it turned out to be a truly very old cognac that grandma had in her closet. And now I can drop the quotation marks around 1874.