Sherry seasoned casks explained

From transport casks to seasoned casks

Sherry is a fortified wine from the area around Jerez de la Frontera in Andalucía, southern Spain. For a long time sherry was shipped abroad in casks. Once emptied, those casks were cheap and plentiful. Whisky distillers filled them. That is how sherry and whisky became linked.

Bulk shipping of sherry largely ended in the late twentieth century. The easy supply of used transport casks went with it. To meet whisky demand, coopers and bodegas began building casks and seasoning them with sherry specifically for the whisky trade. Today most sherry casks used in whisky are seasoned casks.

What seasoning means

A seasoned cask is a new cask, usually built from European or American oak, filled with sherry for a period so the wine soaks into the wood. Seasoning periods commonly run from around one to two years. After seasoning, the cask is emptied and shipped to the distillery, ideally still wet.

Seasoned casks are different from old solera casks, which may hold sherry for decades inside a bodega. Solera casks are rarely sold and highly prized. A seasoned cask is built for whisky and that is no bad thing. It has more fresh oak character and a known, recent sherry history. Our guide to ex-bourbon, sherry and wine casks compares the families.

Sherry styles change the cask

The sherry used for seasoning shapes what the cask gives. The main styles:

• Oloroso. Dry, aged oxidatively, nutty and rich. The classic whisky seasoning: dried fruit, walnut and spice.
• Pedro Ximénez (PX). Very sweet, made from sun-dried grapes. Gives dark colour, raisin, fig and syrupy sweetness.
• Fino and manzanilla. Pale, dry, aged under a layer of yeast called flor. Gives lighter, saline, nutty notes. Less common for whisky.
• Amontillado. Begins under flor, then ages oxidatively. Nutty and dry, between fino and oloroso.

European or American oak

Seasoned casks are made from either European oak, often Spanish, or American white oak. European oak tends to give more tannin, spice and darker colour. American oak gives more vanilla and coconut. A European oak oloroso butt and an American oak oloroso butt produce quite different whiskies, even with the same sherry.

Size matters too. Sherry casks are often butts of about 500 litres or hogsheads of about 250 litres. Our guide to small casks for faster ageing explains how size changes speed and loss.

Check every cask on arrival

Sherry casks have long been treated with sulphur to keep them sound in storage and transport. Too much leaves struck match or rubbery notes that can stay in the whisky for years. Some distillers welcome a trace of sulphur. Most do not want much.

The floor detail we insist on: nose each cask through the bung before filling and reject any that smell strongly of struck match. Note how wet it is too. A cask that arrives dry has lost some of its sherry character and may leak until swollen.

Sherry casks in Indian heat

Sherry seasoned butts are large and active. In a hot Indian warehouse, colour and sherry character can build fast, especially in European oak. That speed can be useful for a young whisky, but tannin can also build to a drying, bitter level.

Sample more often than a Scottish schedule would suggest and blend with gentler casks if needed. Importing seasoned casks also means long shipping times, so plan purchases well ahead and agree with your supplier how the casks will be kept wet in transit. Our guide to sourcing oak casks for an Indian distillery covers the logistics.

Consider buying a few casks of each style rather than a full container of one. A small trial of oloroso against PX, or European against American oak, tells you more about your own spirit in your own warehouse than any supplier brochure. Keep those trial casks in comparable positions so the warehouse does not muddy the comparison.

Buy the cask you need, not the label

A sherry cask is a specification: oak type, size, sherry style, seasoning period and condition. Ask for all five when you buy. Then match them to the whisky you want. Learning to read a cask specification and predict its effect is part of what a distilling course covers in depth.

Your first step: ask your cask supplier to confirm oak type, sherry style and seasoning period in writing for every sherry cask on your next order.

Common questions

What is a sherry seasoned cask?

A cask, usually new, filled with sherry for a period, often around one to two years, to prepare the wood before it is used for whisky.

Are seasoned casks worse than solera casks?

Not necessarily. Seasoned casks are built for whisky with known history and fresh oak. Old solera casks are rare and behave differently.

What is the difference between oloroso and PX casks?

Oloroso casks give dry, nutty, dried fruit notes. PX casks give a sweeter, darker, raisin and fig character.

Why do some sherry casks taste of sulphur?

Sulphur is used to keep casks sound in storage and transport. Too much leaves struck match or rubbery notes in the whisky.