Spirit-run charge calculator
Before a spirit run, low wines from the stripping runs - and often the heads and tails kept from earlier runs - are mixed and brought to strength. This works out the water, the size of the charge and how many boiler loads it fills.
The background is in stripping run vs spirit run and making the cuts.
How to use it
- Measure the low wines. Collect them together, mix, and measure the volume and strength - corrected for temperature with the alcoholmeter calculator.
- Add the feints. Heads and tails kept from earlier spirit runs, if you're recycling them. Set the volume to nothing if not.
- Choose the charge strength. Most pot-still distillers charge between about 25% and 40%: lower is gentler and gives cleaner cuts; higher saves time and energy.
- Enter the boiler. Its capacity and how full you fill it - usually no more than about 80%, to leave room for the charge to expand and foam.
How it works
The alcohol in the low wines and feints is simply added together. Dividing it by the strength you want gives the volume of the charge, exactly. The water is worked out by weight, using the OIML density tables for alcohol and water, so the shrinkage when they mix is allowed for - the simple “volume difference” sum always falls a little short.
If the low wines and feints together are already weaker than the strength you want, no water is needed, and the calculator shows the strength they will have. The pure alcohol figure is what your spirit run starts with; how much of it ends up as hearts depends on your still and your cuts.
Worked examples
20 L of low wines at 30% and 2 L of feints at 60%, brought to 30%, need 2.03 L of water for a charge of 24.0 L - exactly one load in a 30 L boiler filled to 80%.
After a bigger batch, 22 L at 35% and 3 L at 65% make a 32.2 L charge at 30% with 7.25 L of water: two loads in the same boiler.
Where Stilligent fits
Stilligent keeps a recipe for each spirit you make, with its own cut points and, if you like, its own heat settings, and adjusts the cut points for the strength of your wash and the day's air pressure. As the charge is distilled it shows a live estimate of the strength in the boiler and at the head. At the end of the run it raises the power to bring the tails through, then switches off at the finish point - or asks first, if you'd rather keep collecting tails for your next charge.
Every cut you make, and the jars you mark as blended, are recorded, so the recipe moves gently towards your choices from one run to the next.
Questions
What strength should a spirit-run charge be?
Commonly 25–40% ABV. Many distillers settle around 30%: strong enough to be worth the energy, weak enough to run gently and separate heads, hearts and tails clearly.
Should I add feints to the next run?
Many distillers do: heads and tails kept from earlier runs still hold good alcohol and flavour. Foreshots are never kept.
Why dilute the low wines at all?
A weaker charge boils more gently and gives a slower, clearer progression through the cuts. Stronger charges give off more flammable vapour and need more care.
Can I use a wash instead of water?
Yes - some distillers top up a spirit run with wash for extra flavour. Enter its volume and strength as feints and the calculator treats it the same way.
How full should the boiler be?
Usually no more than about 80%, so the charge has room to expand and foam as it heats. Follow your still maker's guidance.
More calculators for distilling
- Heat-up time calculatorHow long your boiler takes to reach the boil, and the energy it uses.
- Ethanol boiling point and vapour strength calculatorWhat a still temperature tells you about the liquid and the vapour above it.
- Reflux column calculatorColumn diameter, power, packing height, output and cooling water.
Free to use, in metric or US units; your settings are remembered on this device. All results are estimates for planning: check strengths with a hydrometer or alcoholmeter. Distil only where it is legal to do so, and never leave a running still unattended.
Underlined terms are explained in the glossary - tap one for a quick definition.