Doubler / Thumper

In short: A doubler (or thumper) is a vessel attached to a column or pot still that performs a second, in-line distillation of the vapor, raising the proof without a separate run. A thumper is a doubler charged with liquid that bubbles, or thumps.

Common in bourbon production, the doubler or thumper lets a distillery boost proof and clean up the spirit in a single pass off the still. The choice and charge of a thumper subtly affect flavor, which is why it is part of a distillery's house process record.

What is the difference between a doubler and a thumper?

Both are secondary pot stills that redistill the column still's output in a continuous bourbon setup. A doubler receives condensed low wines as liquid; a thumper receives the vapor directly, which bubbles through liquid in the vessel and makes the characteristic thumping sound.

What does the doubler accomplish?

It raises the spirit's proof modestly and smooths the distillate, acting as the second distillation without interrupting a continuous process. The proof off the doubler is the number that must stay at or below the legal maximum for the class.

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Related

• Column still
• Pot still
• Distillation