In the thread on the origin of using charred barrels, I pointed to scientific recommendations made in Europe between the 1780's and 1806 to use powdered charcoal to cleanse new spirit and, somewhat later in this period, to char barrels intended to hold wines and distilled spirits.
But what, more precisely,were the problems facing distillers or those stocking wines and spirits? Based on my readings, some of which appear below, they were of two kinds. First, spirit that was distilled at a low proof needed to be rid of its "essential oils", i.e., fusel oils which in excess made the drinks unpalatable. This is the familiar issue of rectification. Second, new barrels and also old ones which were re-coopered or "shaved" in one reference could lend a bad taste to liquids held in such barrels. In some cases, wine (this would not apply to spirits) was re-fermenting by virtue of contact with substances in the wood. Here is a source from 1850, Tizard's book on brewing (a well-known period text), which addresses in some detail the problem of cask taint. Note that Tizard at one point refers to the problem as common to brewers and distillers (see pp. 493-498):http://books.google.com/books?id=Ui4tAA ... #PPA494,M1
As can be seen, the contact of water with the cask, e.g., when it was washed, could cause formation of fungal agents. Albumen in the wood was identified as one of the causes. This could give the beer a bad taste. Thus, charring, mentioned as one solution by Tizard, was a way to destroy the albumen and render the cask "inert" in this sense. However, as Tizard mentions, numerous other solutions presented themselves: steam-cleaning, the application of dry heat, and use of water in the brewery that had a chemical composition that would retard the spoilage mentioned. Later, lime and sulphur were used to sweeten the casks. Of course, with distilled spirits, the congener problem, i.e., for whiskey and other traditional spirits, remained. The charred barrel was also an answer to this due to the effect of carbon on the resting spirit.
Obviously, both old and new casks were charred for these purposes. To this day in Scotland, I believe most casks used to age whisky are used casks that are broken down and rebuilt. The staves get a charring/re-charring to help keep the wood sweet and delay its degradation. In Canada, ex-bourbon barrels often are re-charred to similar intent. While the charring may impart some taste from a residual red layer, I believe generally this is not the case. The red layer is exhausted, or mostly, in the first application of the barrel, to make bourbon.
In the United States, bourbon barrels by law may only be used once. I think it is fair to infer that once bourbon was kept sweet and free from decay for a long enough time by the charring layer, it was perceived that its taste improved and this result could only be achieved if the barrels were used once. This aspect of bourbon's evolution is (clearly) purely domestic. This is what I called the "lucky happenstance" in the other thread mentioned. But even then, it took people willing to make the investment in new barrels to ensure a quality product. At the time, America had a lot of oak available. Period English accounts attest to the large amounts coming into Britain for coopering purposes - there was lots to go around. Thus, what perhaps was a motivation to use new wood over used barrels - high demand for whiskey and closeness to supply of new wood sources - later became a requirement to maintain the best bourbon that could be made. One can conceive that new barrel bourbon could have been blended with used barrel "bourbon"; this did not occur for the product we know today, and that is legally regulated, as Bourbon. (It did occur in a certain sense, for American blended whiskey).
Was the new charred barrel used initially because of the fine flavor it imparted? I don't think so. I think its use started because there weren't enough well-seasoned old barrels to go around and, distillers having to use new barrels, they decided to have them charred as the best way to avoid tainting the whiskey with fungal flavours and possibly also to avoid the resinous, tannic, taste that fresh oak can have. (As to where they might have got the idea, see again the other thread mentioned). Even old barrels would have been an issue in this sense once cleaned thoroughly for re-use - because it exposed fresh old wood and its organic agents - but the large availability of fresh wood to make barrels in America impelled distillers' to use new barrels because they could sell all the whiskey they could make. I was struck, in reading congressional testimony of distillers in hearings related to whiskey excise and bonding, how hard it was to procure genuine, unadulterated Bourbon and rye whiskey in America in the mid-1800's. It clearly was a prized product almost from its inception.
Hence the issues associated with new barrels that needed to be addressed with confidence, and they were. But what is more, and as noted above, those risks presented opportunity - to perceive that a unique, high quality product could be made if the charred barrels were used only once. The stories about bourbon being an accident and resulting from use of barrels burned in a fire or through a coopering error are, I believe, a way to explain Bourbon's history that is appealing; they might be viewed as a kind of narrative device. The origin of the charred barrel is I think much more pragmatic and once again scientifically driven. On the other hand, bourbon's creation did rely on a perception someone made that this new charred barrel whiskey wasn't just very good and maybe justifying a Grade A or blending it with the Grade B stuff, but was deserving of being a product unto itself. That was a connoisseur's call, a made-in-America judgment. Inevitably, business factors played a part but that does not change this essential perspective. In that sense, bourbon was a home-grown product of the people, not an industrially-driven product as Canadian whisky has been since its beginnings, or Scotch blended whisky is. The scale of bourbon production for a long time (small or on the small side) is in synch with this way of looking at it.
Tonight I will post more references, all from about 1810-1880, showing in further detail how problems caused by new barrels and new mashing and fermenting vats were studied and overcome: this period is after, that is, the theoretical solution in relation to charred vessels had been devised.