Since the Scotch whisky industry uses bourbon barrels I was wondering about the preparation processes employed. Evidently, at least some, if not all "de-char and re-fire" the barrels. I seems this would remove the majority of prior spirit influence on the new pour malt. Can anyone speak to this frequency of this type of barrel prep and the amount of wood soaked spirit left that could still add to the malt whisky flavor? Obviously, we detect bourbon or sherry or wine notes is malts but I wonder if the "de-charring and re-firing" is universal?
What about 3rd fill or more barrels?