I just returned from a business related journey to the Black Forest in southern Germany. Apart from its famous smoked ham, this region is known for growing high quality cherries, most notably used for the production of Black Forest Cake and Kirschwasser, eau de vie made from cherries. While recapitulating the recent debate about bottle aging of whisky, something struck me. I have known it for years, but only know I saw the relation to that topic.
Why Old Kirschwasser is Crystal Clear
While most Kirschwasser ist sold and consumed unaged, there are also premium bottlings of aged Kirsch available, usually around 3 to 5 years old, sometimes up to 12. And what might be surprising for someone only used to Whisky and Brandy, is that even the oldest Kirschs are clear as spring water!
The reason for this is simple: Almost all Kirschwasser is aged in large glass or steel vessels instead of wooden casks. There are very few cask aged Kirschs available, but the vast majority of aged Kirsch is clear. Distillers use glass or steel because they want to maintain the plain fruit character of the spirit, deliberately rejecting wood casks because their influence would interfere with the pure fruitiness.
And even without the use of casks, glass or steel aged Kirsch tastes smoother, rounder and fuller than the standard “newmake”. This tradition is centuries old (well, steel vessels are of course a modern adaption for high-output distilleries). And you can bet that hundreds of distillers wouldn’t bother to let their spirit rest for years if there was nothing happening in the vessels.
If Kirschwasser Does, So Must Whisky
It is a fact that fruit eau de vies will change their taste even in a sealed glass vessel. A sealed whisky bottle is not a different physico-chemical system than a glass balloon containing Kirschwasser. Anyone who still thinks that a sealed bottle is an inert system is urgently advised to reconsider their position.
Of course I welcome all critical voices, but I think it needs substancial evidence to disprove this hypothesis.