Feed
Composition and flow rate determine what the still must separate.
Universal Foundation 02
Distillation
in Spirits
Concentration, Selection & Spirit Style.
Distillation concentrates alcohol and selects volatile fractions from a fermented liquid. Still design, reflux, copper contact and collection decisions influence the strength and style of the new spirit.
Scope This foundation begins with fermented alcoholic liquid and ends with the collected spirit. It explains the common principles before comparing their use in Scotch, Canadian whisky, Jamaican rum, Tequila, Cognac and neutral spirit production.
Start with concentration and selection →Continue where you left off →Distillation sequence
- 01Fermented liquidAlcohol, water and congeners
- 02Heat + vapourVolatile fractions enter the vapour
- 03RefluxManaged reflux increases rectification
- 04Still operationBatch, continuous, copper and design
- 05Collected spiritSelected fractions at a chosen strength
After this foundation
01
Explain how distillation concentrates alcohol and selects fractions
02
Compare batch and continuous distillation systems
03
Describe how reflux, copper contact and collection strength influence spirit style
Answer first
What does distillation do in spirits?
Distillation heats a fermented liquid so volatile compounds redistribute between liquid and vapour, then condenses and collects selected fractions. It concentrates alcohol, while reflux, copper contact, cuts or draw points and collection strength help determine which compounds remain in the new spirit.
Foundation sequence
Begin with the fermented liquid, then examine volatility, batch and continuous operation, reflux, fraction selection and copper contact.
01Distillation concentrates and selects02Volatility determines vapour composition03Pot stills operate in batches04Cuts separate heads, heart and tails05Reflux increases rectification06Column stills use plates or packing07Copper contact and still design08Collection strength and compositionREFSources & Further Reading
Distillation concentrates and selects fractions
Fermentation creates alcohol and flavour compounds. Distillation changes their concentrations and proportions.
Fermented liquid contains many compounds
A fermented wash, wine, beer or agave liquid contains water, ethanol and many congeners. Heating creates a vapour that contains a different proportion of these compounds, but it is never pure ethanol.
The vapour is condensed back into liquid and selected fractions are collected as spirit. Other fractions may be recycled, removed or left behind in the still.
Distillation concentrates alcohol and selects the desired volatile fractions.
InputFermented liquid containing alcohol and congeners
HeatVolatile fractions enter the vapour
ContactVapour and liquid exchange material
OutputCollected spirit and separated fractions
Volatility determines vapour composition
More volatile compounds are present in a greater proportion in the vapour, but the vapour remains a mixture.
Boiling points do not separate compounds completely
At a given pressure and liquid composition, the vapour contains a greater proportion of the more volatile compounds. Condensation returns the vapour to liquid form, and repeated evaporation and condensation can increase separation.
Water, ethanol and congeners interact inside the mixture. As the composition changes, their behaviour also changes. A pure boiling point therefore cannot predict the exact moment a compound will appear or disappear during spirit distillation.
Liquid mixtureWater + ethanol + congenersComposition changes during distillation
⇄Vapour–liquid contactHeat + mass transferCompounds move between phases
⇄Vapour mixtureDifferent proportionsMore volatile compounds are more concentrated
Pot stills operate in batches
The still is charged, heated and emptied before the next distillation begins.
01ChargeAdd the fermented liquid or intermediate spirit
02HeatCreate vapour from the changing liquid charge
03ContactUse surfaces and geometry to create reflux and exchange
04CondenseTurn outgoing vapour back into liquid
05CollectSeparate, redirect or retain changing fractions
The composition changes during the run
As volatile fractions leave, the liquid remaining in the pot contains less alcohol. The composition and strength of the vapour and collected distillate therefore change throughout the run.
A second or third distillation can increase concentration and allow further fraction selection. Scotch malt whisky commonly uses two pot distillations, while Cognac uses the première chauffe and bonne chauffe.
Batch distillation can be highly controlled
Charge size, fill level, heat input, distillation rate, still design, condenser and cut points can be measured and repeated precisely.
Cuts separate heads, heart and tails
The concentrations of volatile fractions change during the run, but the fractions overlap rather than separating into pure groups.
Earlier distillateSelected collection windowLater distillate
Heads / foreshotsHeart / spiritTails / feints
Cut points determine what is collected
Distillers may use time, flow rate, strength, temperature, aroma, taste and analytical data to decide when to change collection vessels. Heads and tails may be discarded, recycled or used in another component.
Changing the cut points changes the proportions of compounds in the heart. It does not include or exclude one compound completely because volatile fractions overlap throughout the run.
Vocabulary
Heads, heart and tails are useful terms for batch distillation. Continuous stills may use different names for their product, recycle and removal streams.
Reflux increases rectification
When part of the vapour condenses and returns as liquid, further vapour–liquid contact increases separation.
Rising vapourMore volatile compounds are more concentrated
→CondensationPart of the vapour becomes liquid
→Returning liquidReflux creates further contact
More reflux increases rectificationReflux can occur naturally or be controlled
In a pot still, vapour can condense on cooler internal surfaces and return to the pot. Still shape, fill level, heat input and surface temperature influence the amount of reflux. In a column still, condensed liquid is deliberately returned downward while vapour rises.
Greater reflux generally produces a more highly rectified spirit, but this is a choice of style rather than an automatic measure of quality.
Pot still
Internal reflux
Still design and operation influence how much liquid returns to the pot.
Column still
Controlled reflux
Rectification plates force vapour through the liquid held on each plate.
Column stills use plates or packing to manage reflux
Fermented liquid can enter continuously while spirit and other fractions leave from selected points.
OverheadConcentrated vapour → condenserRefluxCondensed liquid returned downward
Plates or packing manage reflux
FeedFermented liquid enters continuouslyDrawsProduct, recycle or removal streams
Stripping and rectifying sections perform different functions
The stripping section separates volatile fractions from water and non-volatile material. The rectifying section uses plates or packing to manage reflux and increase separation. On rectification plates, vapour is forced through a layer of liquid; packing creates a large surface area for condensation and reflux.
Column stills can produce characterful spirit, lighter blending components or highly rectified neutral spirit. Feed composition, number of plates, reflux, draw points and collection strength determine the style.
Plates or packing
Plates force vapour through liquid; packing creates many opportunities for reflux.
Draw points
Spirit and other fractions are collected, recycled or removed.
Copper contact and still design influence spirit style
Still shape, construction material and condenser design influence reflux, copper contact and sulfur management.
Copper contact
Copper surfaces can help remove or transform some sulfur compounds. The result depends on where contact occurs, surface condition and the wider system.
Still geometry
Height, neck shape, boil ball, plates and connecting pipework influence flow, entrainment, residence and internal reflux.
Condenser
Worms, shell-and-tube units and other condensers differ in surface area, coolant pattern and copper contact.
Operation
Fill level, heat input, pressure and run speed change how the physical system behaves.
Copper helps remove some sulfur compounds
During distillation, copper can react with sulfur compounds and reduce their concentration in the collected spirit. The effect depends on where the copper is located, its surface condition and the amount of contact.
A still does not need to be made entirely from copper. Stainless-steel equipment may include copper plates, packing or inserts. Still shape, cleaning, reflux, fraction selection and condenser design must also be considered.
Collection strength and composition determine the new spirit
Strength measures alcohol concentration. Spirit style also depends on which congeners were retained and in what proportions.
Spirit categoryDistillation approachApplied chapter
Scotch whiskyCompare batch pot distillation for malt whisky with continuous column distillation for grain whisky.Open Scotch →Canadian whiskyProduce lighter base whiskies and more characterful flavouring whiskies for blending.Open Canadian →Jamaican rumCompare double-retort pot stills with column stills used to produce different marques.Open Jamaican →TequilaCompare permitted pot and column stills, number of distillations, reflux and fraction selection.Open Tequila →CognacExamine two regulated pot distillations and the selection of eau-de-vie for maturation.Open Cognac →Neutral spiritUse managed reflux and rectification to produce highly rectified spirit at the required strength and composition.Open rectification →Collection strength
Used for regulation and process control, but it does not describe all congeners present.
Selected fractions
Identify which fractions were collected and which were recycled or removed.
Post-distillation operations
The spirit may rest, mature, blend, dilute, filter or undergo another distillation.
Proof & Principle check
01Is the explanation accurate?
02Is it useful by itself?
03What does it link to?
04What links back to it?
RefSources & Further Reading
References
Sources behind the foundation
The mechanism and category applications were checked against peer-reviewed research, official category rules and professional study standards on 27 August 2026. Category examples remain examples, not universal rules.
Distillation science
Beverages · Sources of Volatile Aromatic Congeners in WhiskeyPeer-reviewed review of fermentation, distillation and maturation contributionsJournal of the Institute of Brewing · Copper and distilled spiritResearch on copper location and sulfur-compound formationMolecules · Sulfur compounds in distilled beveragesPeer-reviewed review of sulfur chemistry and copper interactionWSET Level 3 Award in SpiritsCross-category production and style-analysis frameworkOfficial category evidence
HMRC · Producing Scotch WhiskyCurrent UK guidance and Scotch Whisky technical fileBNIC · Cognac productionOfficial double-distillation sequence and Charentais methodCRT · NOM-006-SCFI-2012Official Tequila production standardJIPO · Jamaica Rum GIOfficial geographical-indication specificationJustice Laws · Food and Drug RegulationsCanadian whisky identity and production frameworkeCFR · §5.142 Neutral spirits or alcoholCurrent United States neutral-spirit identity standardThe takeaway
Understand the separation.
Then consider what was collected.
Distillation concentrates alcohol and selects volatile fractions. Still design, reflux, copper contact, cut or draw points and collection strength influence the composition and style of the new spirit.