How the type and/or design of the condenser can affect the style of malt whisky that is produced?
The two types of condensers used in Scotch whisky production are the worm tub and shell+tube. Effectively, both limit the amount of copper-contact with the spirit and also assist in condensing the alcoholic vapors back into a liquid.
The worm tub combination is simply a long, copper pipe coiled into multiple layers that is submerged in a large vat or “tub” that has a constant supply of cold water running through it. When the hot, alcoholic vapors enter the top of this tubing they begin to cool and condense back into a liquid that is then collected at the bottom of the coiled-copper tubing. During this time the vapors interact with the copper tubing which pulls out some (but not all) of the sulfur compounds and unwanted cogeners. Overall this process has low copper-to-spirit contact and requires a large-amount of running water. This application still leaves some of those compounds in the distillate that, where desirable, can add a sulfur-quality or “meatiness” to the spirit.
In contrast, the shell+tube condenser consists of a series of tubes that are contained in a shell-like chamber with an opening at each end. Unlike the worm-tub condenser, cold liquid is pushed through the tubing at a constant rate and temperature. The hot, alcoholic vapors that enter the top of the shell-chamber, engulf the cold tubing and start condensing into a liquid that is then collected at the bottom of the chamber. Stainless steel or copper can be used in this application. When using copper, it is more efficient (in that is has a higher copper-to-spirit ratio) than the worm-tub condenser when trying to remove supfur compounds. In turn this creates a lighter, cleaner-style spirit.
