Sherry is a type of fortified wine made with a variety of of white grapes (but mainly Palomino) from near the city of Jerez de la Frontera in Andalusia, Spain. This area of Spain is dry and hot in the summer with temperatures reaching in excess of 40ºC. This would normally kill most grape vines, but the rich clay soil and moist sea breezes, help the vines to retain moisture.
“Sherry” is an anglicisation of Xeres or Jerez and the British love affair with this wine started in 1587 when Sir Francis Drake sacked Cadiz and stole 2,900 butts of sherry. In subsequent centuries a more peaceful and vibrant trade started between Jerez and Britain with bottling taking place in the port cities of London, Bristol and Glasgow. Whisky distillers quickly realised the potential of the leftover sherry butts and started to use them make whisky casks. Most good quality sherry casks used American oak for ageing Sherry because it is strong and imparts less tannin and colour to the wine.
Until the 1930s the use of sherry casks was commonplace in Scottish whisky production, but due to the limited availability of casks during the Spanish civil war, whisky distilleries switched to using more American bourbon casks instead. Today well over 90% of Scottish whisky casks are American bourbon, which means many people have never had the chance to taste a “sherry cask single malt”.
Sherry casks are now very rare, and very expensive. To get around this, until recently, some distilleries would “cheat” and use a concentrated wine called “paxarette” and apply it under pressure to a cask to make it a “sherry cask” but this was recently banned. Another lesser “cheat” that is still widely used today is the “envinado” process which uses cheaper Spanish oak and inferior quality sherry to make “sherry casks”.