The importance of copper contact in whisky distillation
All pot stills used in the Scotch whisky industry are made from copper. This easy to shape common metal is an effective conductor of heat. Copper is a good catalyst which means that it speeds up chemical reactions. Copper also reacts with various compounds in the gaseous phase. Most notably, copper removes some of the sulphur containing compounds from the wash.
Here, we are seeing how copper influences the character of new make spirit during the distillation process. This is especially important to the condensing process of gases from the still being collected as liquid distillate (see our previous diagram about Reflux).
The type of condensing system used, and the extent of copper used in that system (some are replacing elements of the system with stainless steel) will have a significant impact on the new make spirit character.
Two types of condensers are used in Scotland:
- Worm tubs
- Shell and tube condensers
Worm tubs (top) and shell and tube condensers (bottom) produce different types of new make spirit.
These two condenser systems produce different types of new make spirit. Worm tubs generally produce a more sulphury or meaty spirit than a shell and tube condenser. Modern shell and tube condensers tend to be much more efficient and provide better copper contact than the old-style worm tub condensers.