The idea that whisky flavour is not determined by ingredients and distillation alone is attracting interest. Microbial communities settled in the washback are said to create a substantial part of the character.

Yeast is traditionally used for whisky fermentation, but wooden washbacks also host a range of other microorganisms including lactic acid bacteria. The acids and esters they produce add layers of fruit aroma and tartness.

The problem began when wooden washbacks were replaced with stainless steel for hygiene and efficiency. The process became more stable, but critics note that the microbial environment giving particular distilleries their character disappeared with it.

Attempts to revive a taste from forty years ago start with digging through records, because fermentation times and temperatures, yeast strains, equipment materials and cleaning methods all have to be reproduced.

This is not a story about whisky alone. The relationship between microbial communities and production environments is again a subject of study across fermented foods, from soy sauce and doenjang to kimchi, Shaoxing wine and baijiu.

It is also striking that verifying whether a revival matches the original is itself difficult. Memory is imprecise, and surviving old bottles change with the years.