After about forty-eight hours, the yeast in a washback has done most of its work: the sugar has become alcohol. But in the quiet second half, bacteria naturally present in the wood begin a slow malolactic fermentation, building esters that smell of pear, apple and pineapple.
Those esters survive distillation and give our new make its fruit. It costs us capacity — we fill half as many casks as a faster distillery of our size — and we think it is worth it.