MODULE 08 · 9 MIN
Warehouses, Time, Evaporation and Alcohol Strength
Dunnage warehouses usually store a few layers of casks on earthen floors; racked warehouses can hold many casks on structured racks. Temperature, airflow, humidity, cask position and building design influence maturation, although cask-to-cask variation remains significant.
Water and alcohol evaporate through oak—the “angel’s share”. Volume generally falls and ABV may rise or fall depending on conditions. A cask must remain at or above 40% ABV if it is ultimately to be bottled as Scotch Whisky, making periodic measurement important for long maturation.
Key ideas
Warehouse conditions influence but do not fully control maturation.
Evaporation reduces cask contents over time.
Long-held casks require strength and volume monitoring.
Glossary
- Angel’s share
- Spirit and water lost through evaporation during maturation.
- Regauging
- Measuring a cask’s volume and alcoholic strength.
Three-question self-check
Pause before moving on.
1. Can you explain: Warehouse conditions influence but do not fully control maturation.
Warehouse conditions influence but do not fully control maturation.
2. Can you connect: Evaporation reduces cask contents over time.
Evaporation reduces cask contents over time.
3. Can you define “Angel’s share” in your own words?
Long-held casks require strength and volume monitoring.
Sources & further reading
- SWA — Personal investment in a Scotch Whisky caskScotch Whisky Association
- SWA — Scotch Whisky FAQsScotch Whisky Association
Last reviewed: 2026-08-09