I append at the end of this note what I consider a significant finding, namely that in 1806 in "A Journal of Natural Philosophy, Chemistry and the Arts" (an English science and chemistry journal), the recommendation was made to age spirits in a new charred barrel.
The article, by William Nicholson, reviewed an experiment to char the interior of a barrel (here called a cask in English usage) to store water in ships. Nicholson indicates that the charcoal layer in the barrel protected the water from substances in the wood which would produce "putrefaction". Nicholson then suggests that wine might be stored the same way, to protect it from similar spoilage or (I infer) flavour change. He notes that wine when kept in glass is thus protected, and he was looking for a way to store wine in a barrel that would have the same effect. Finally, he advises that "spirituous liquors" should also be stored in a new charred cask. He is not talking about toasting, the discussion makes it clear he is envisaging a blackening of the barrel interior.
He acknowledges that storage in wood is partly good for spirits, but states that wood also has the capacity to impart negative qualities. He states this is why re-used barrels are preferable to new ones for storage of wine (still a desideratum for most wine-makers - and distillers outside the U.S.).
Wood storage of spirits has the capacity to eliminate fusel oils, but it imparts its own flavour and this may have been seen as a fault or type of spoilage at the time. We are speaking of 1806, an early time in the understanding of spirits maturation.
I wonder if someone put Nicholson's theory into practice in the whiskey-making States in America. American distiller Samuel M'Harry, writing just a few years later, notes that whiskey held in wood will acquire some colour and "maybe some taste". While he liked the result for his own consumption, the tenor of his remarks is not to keep whiskey in wood too long if its use is to mix with beer or as a base for (in effect) various cordial preparations. So, maybe someone in the U.S. followed Nicholson's advice in an attempt to keep whiskey long enough to remove objectionable fusel oils but (at any rate) prevent it from becoming too woody in taste. Perhaps charred barrels that had held water were later used to hold whiskey either to secure benefits similar to what was obtained for water or simply because these barrels were available, but I do not rule out the former possibility. We tend in the Internet age to assume that information was not widespread in a given art in former centuries but this was not always so as e.g., is shown by M'Harry's familiarity with the then emerging method of steam distillation. Also, it may have been that early distillers in America had new barrels available to them more easily than old, I can conceive of a number of reasons why this may have been so.
It is true that M'Harry speaks of disinfecting wooden vessels with a fire made from hay, without any reference to Nicholson's article or any prevailing theory of science. However, M'Harry seems to be talking about mashing and fermentation vessels, not whiskey aging barrels. There is also his reference to keeping whiskey in a barrel that is "branded", but I doubt that meant the firing of a barrel to keep whiskey in. (Although, this is not 100% clear). We have discussed before (on this board) the significance if any of these two references in M'Harry's book to an apparent use of fire to sanitize or prepare wood vessels used to make and store whiskey.
I always felt the idea that bourbon derived as a lucky by-product of using barrels burned in an accident or through a coopering error to be unlikely. I was a party more to the theory that some re-used and even new barrels were charred intentionally to sanitize them (cleanse of off-odors) and the use of such barrels to hold whiskey later became systematic. The latter theory still is plausible, of course. The tannins and flavours imparted by a new oak barrel can be overpowering and strong: I once had beer stored for a short time in a new uncharred oak keg, and it was almost undrinkable. Thus, it is possible that charring a new barrel was regarded as a form of sanitization, independent of anything Nicholson was suggesting. But also, Nicholson may have spurred the practice either directly or indirectly.
I believe it has not been known until now that a scientist as early as 1806 was advising that new charred barrels be used to hold not just wine but spirits, and not to deodorize the barrel as such but to prevent (as it was thought) contact between the spirit and the wood frame of the barrel so as to retain the best characteristics of the spirit. The writer of the early 1800's Kentucky grocer's letter Mike Veach has found advising a distiller to char the inside of the barrels may have been a science buff, or may have been told of the likely benefits of the process by a learned man, or by a seaman, or may have hit on the idea himself, independently: the possibilities are endless but I now believe someone concerned with the storage of whiskey may have applied Nicholson's theory one way or another. In effect, he was inviting people to do so because he states testing was needed to validate his idea...
Europe never came to terms with using new barrels to store wine and spirits despite Nicholson's suggestions, but America did, and for reasons different than Nicholson projected because a new charred barrel does change the flavour of whiskey and the change does derive from the wood but in an unanticipated and, ultimately, gratefully received way. Progress is often the result of a combination of scientific insight and chance factors.
Here is the source, see pp. 225-228: http://books.google.com/books?id=thAAAA ... ES#PPP7,M1