Cask-finished whisky is common these days, but in the early 1980s, no one had ever done it before. David Stewart began experimenting with finishing single malt scotch in special casks at Balvenie Distillery, a technique he has continued throughout his career of over 50 years and counting. Here he explains how the different finishing casks—sherry, rum, port, et cetera—impact the final flavor of the whisky—and which cask finishes haven’t been a success.