How to Optimize Copper Contact in Distillation

Copper has long been used in distillation for its heat conducting properties and malleability; both properties make it easy to use in still construction and operation. Furthermore, copper’s corrosion-resistance makes it an excellent choice when building stills; yet its chemical composition makes copper an indispensable ingredient when producing spirits.

Copper acts as a catalyst to accelerate several chemical reactions involved with spirit production, including esters formation which contribute fruity and aromatic aromas in whisky. Esters form when naturally produced acetic acid from fermentation interacts with ethanol at the surface of copper to form ethyl acetate – which has an irresistibly sweet fruity scent!

Copper can also be used to eliminate unwanted sulfur compounds formed during fermentation and distillation processes, through interactions with copper ions that interact with these compounds to bind them and form copper sulfide crystals which will precipitate out of solution upon emptying of the still at the conclusion of distillation, thus eliminating unpleasant sulphurous flavors from final products.

Copper usage plays a key role in the quality of new make spirits produced, with more copper leading to lower concentrations of undesirable sulphur compounds and consequently producing superior spirits. Large stills that use large volumes of copper tend to produce better spirits than those with less copper, and many producers now opt for tubular bundle condensers over traditional worm tubs as these allow more intense copper contact than their predecessors.