Animated pot still
Heat, boiling, vapor travel, condenser flow and receiver drip respond to actual collection rate.
Receiver cuts
Cut timing uses recovered ethanol progress, spirit style, vapour ABV and temperature.
Live distillation curves
Hover any chart for exact values. Click to expand full run history. VLE diagram shows live operating point on the equilibrium curve.
How to use this simulator
The simulator runs a full pot still batch distillation from ambient temperature to the end of the run. Every parameter affects the physics.
- Set your wash. Enter boiler volume and wash ABV. A typical sugar wash is 8–12%, a grain wash 6–9%, and a fruit wash 8–14%.
- Choose a spirit style. Each preset adjusts cut thresholds — vodka uses the tightest hearts window, brandy the widest. Pot efficiency and cut timing adjust automatically.
- Set heat input. A 2–3 kW element is typical for home use. Higher heat produces more vapour per hour but can reduce separation quality.
- Set methanol ppm. Sugar washes are typically 50–300 ppm; fruit washes can be 500–3,000 ppm. The methanol chart shows relative depletion through the run for transparency — cut on taste, smell and the acetaldehyde-driven harshness of the first fraction, not on a methanol number.
- Click Start. Use the speed slider (1–50×) to run at pace. The animated still, all six charts, and the fraction jars update in real time.
- Open Advanced for realism. Set your local atmospheric pressure (altitude lowers boiling point), a thermometer error if yours reads off, ambient room temperature and still insulation (change heat-up time, not the boiling point), and theoretical plates if your still has a dephlegmator, packing or a tall column above the pot.
- Export or review. When the run ends a summary card shows yield, estimated bottles and methanol discarded. Export CSV to analyse the full run data.
Detailed calculation model
This simulator uses a dynamic batch pot-still model grounded in real thermodynamics: ethanol concentration falls, vapour strength declines, head temperature rises from ambient to bubble point, production rate responds to heat input, and the run progresses from heads into hearts and tails.
1. Boiler inventory
The boiler tracks ethanol, water and methanol volumes separately. As product is collected, each component is removed according to its instantaneous vapour composition, conserving total moles at each timestep.
2. Van Laar VLE
Activity coefficients use the Van Laar model (A₁₂ = 1.6798, A₂₁ = 0.9227), more accurate than 2-suffix Margules near the azeotrope. Bubble-point temperature is solved numerically via bisection at each step, giving a realistic temperature curve throughout the run.
3. Theoretical plates
The pot itself is stage 1, limited by pot efficiency (imperfect boil and vapour-liquid contact). Setting theoretical plates above 1 in Advanced adds further ideal Van Laar equilibrium stages on top — a dephlegmator, packing, or a tall lyne arm — cascading the stage-1 vapour upward and re-equilibrating at each stage, the same way a real column pushes composition further toward the azeotrope with each additional plate. A fractional plate count interpolates between the last full stage and the next, matching the 1.1–1.3 typical for a real pot still. This directly re-uses the same VLE model rather than a fixed relative-volatility shortcut, so separation naturally weakens near the azeotrope the way real columns do. Methanol tracking is not re-staged by this cascade in this version.
4. Thermal-mass heat-up
Temperature rises as dT/dt = (Q·η − Q_loss) / (m·Cp), where m is boiler mass and Cp is the mixture heat capacity. Q_loss is a lumped wall heat-loss term set by the gap between current temperature and ambient, scaled down by the insulation setting — a simplified stand-in for a full per-surface heat-transfer model, not a claim of matching that level of detail. At default settings (20°C ambient, 50% insulation) a 25 L boiler at 2.4 kW takes roughly 55–65 minutes to reach bubble point, in line with real distillery experience; a bare, uninsulated still or a cold room noticeably slows this down.
5. Energy-balance vapour rate
Vapour rate is derived from Q_vap = Q_in × ε_still, divided by the mixture latent heat ΔHvap (ethanol 841 kJ/kg, water 2260 kJ/kg, weighted by distillate composition). Rate naturally decreases as ethanol depletes and more energy goes into vaporising water.
6. Methanol (3rd component)
Methanol is tracked as a dilute 3rd component using its own Antoine equation and a fixed activity coefficient (γ = 2.2). It is more volatile than ethanol and depletes earlier in the run, but not sharply enough for a small foreshots cut to remove it entirely — some carries into heads and hearts regardless of cut size. The chart is shown for transparency about relative volatility, not as a foreshots safety cutoff. The real reason to discard the first fraction is acetaldehyde and other highly volatile congeners, not methanol quantity.
7. Cut classification
Cuts use spirit-specific profiles based on the DistilCalc cuts calculator. The primary driver is recovered ethanol progress, with vapour ABV and temperature used as guardrails to prevent misclassification during heat-up and late-run decay.
The simulator solves the temperature at which total pressure reaches your local atmospheric pressure (1013 hPa at sea level by default), then calculates ethanol vapour mole fraction from modified Raoult's law and converts that back to a condensed liquid ABV. This captures the full distillation curve — from the steep early rise to the gradual tailing-off as the hearts window closes.
- Whisky: balanced pot-still profile, keeping moderate congeners for grain character.
- Rum: slightly wider hearts, allowing more late character for heavier styles.
- Brandy: wider and lower cuts — fruit spirits retain more character deeper into the run.
- Gin: clean, tight profile to avoid solventy or heavy notes masking botanicals.
- Vodka: narrowest hearts window, prioritising neutrality and a clean spirit.
The speed slider goes to 50×. Internally the simulator divides each animation frame into small calculation steps, so high-speed settings are less likely to skip past the hearts window.
Whisky Tasting Journal: Pair your simulated runs with real batch records. 100 structured entries, score /100, buy-again rating. 6 x 9 in, 116 pages, cream paper.