Distillation yield: tracking foreshots, heart and feints — and what a good spirit yield per tonne looks like

Yield is the number a distillery manager carries in their head: how much spirit did we get from what we bought? It drives malt purchasing, costing, and the awkward conversations when it dips. This guide walks the alcohol from mash to spirit receiver, explains how yield is calculated and benchmarked, and covers the record-keeping that turns "yield is down 2%" into "tank 4's fermentations are under-attenuating". General guidance — every distillery's numbers are its own.

The journey, stage by stage

Mashing.Milled malt meets hot water; starch becomes fermentable sugar in the worts. What matters for yield: the malt's laboratory extract (how much fermentable material a tonne can give) and how efficiently the mash tun recovers it. The malt analysis certificate carries a predicted spirit yield (PSY)— the LPA per tonne the lab says is achievable. That figure is your denominator's promise.

Fermentation. Yeast converts sugar to alcohol. The washback's final wash strength(commonly ~7–9% ABV) and attenuation tell you how much of the extract became alcohol. Short or stuck fermentations are the most common silent yield-killer: the wash looks like wash, but there's less alcohol in it.

Wash still. The wash is distilled to low wines, typically ~21–25% ABV. Nearly all the wash's alcohol carries over; what remains in the pot ale should be a trace (worth spot-checking — alcohol left in pot ale is yield going to the draff lorry's cousin).

Spirit still. The low wines (charged together with recycled foreshots and feints from previous runs) are distilled again, and the stillman — or the automation — makes the cuts:

• Foreshots (heads):the first runnings, high in volatiles you don't want. Diverted to the feints receiver. Typically cut on time and/or the demisting test.
• Heart (middle cut / new make):the keeper. Collection often starts somewhere around ~72–76% ABV and ends somewhere in the ~60s, but the cut points are a house signature — they define the spirit's character as much as its quantity. Wider cuts mean more litres and a different (not necessarily better) spirit.
• Feints (tails):the remainder, down to the point where the still is "spent". Diverted to the feints receiver, with the spent lees going to disposal.

The recycle loop.Foreshots and feints join the next charge (the low wines and feints receiver — the LWFR, in HMRC's vocabulary and ours). Their alcohol is not lost; it goes around again. This is why a single run's "heart percentage" is not yield — the loop means each charge contains alcohol from previous runs, and the only honest yield calculation is done over a period with the loop's start and end stocks counted.

The yield calculation

Over a production period (a week, a month, a season):

Spirit yield (LPA/tonne) = LPA collected as new-make spirit ÷ tonnes of malt mashed

…with two corrections that separate real measurement from wishful thinking:

1. Charge balance.Add the opening stock of the low wines/feints loop and subtract the closing stock (in LPA). If the loop grew by 300 LPA over the month, that alcohol came from this month's malt but isn't in the receiver yet; ignore it and the month looks worse than it was. Draw the loop down and the month looks better than it was.
2. Count everything that left.Spirit sent to the receiver, plus samples, plus any recorded losses. Alcohol is a conserved quantity — if it isn't in the receiver, the loop, or a recorded loss, your measurements disagree somewhere.

A worked month

• Malt mashed: 120 tonnes (PSY on certificate: 416 LPA/t → theoretical 49,920 LPA)
• New-make collected: 48,100 LPA
• LWFR: opening 2,900 LPA, closing 3,350 LPA → loop grew by 450 LPA
• Recorded losses and samples: 110 LPA

Adjusted production = 48,100 + 450 = 48,550 LPA attributable to the month's malt. Yield = 48,550 ÷ 120 = 404.6 LPA/tonne, i.e. 97.3% of PSY.

That last ratio — actual against the malt's own predicted yield — is the fairest benchmark, because it normalises for malt quality. Chasing a neighbour's headline LPA/tonne with different malt specs is comparing harvests, not distilleries.

What "good" looks like

As planning ranges for conventional malt whisky distilling:

Treat these as orientation, not gospel: mash bill, yeast, fermentation length, still design and cut philosophy all move the numbers, and some houses deliberately trade yield for character. The managerial point is not the absolute figure — it is knowing your own baseline tightly enough that a 1–2% drift is visible in weeks, not year-end.

Diagnosing a yield drop

Because the process is sequential, per-stage records localise the problem fast:

• Actual vs PSY down, wash strength fine → look at distillation: losses, cut discipline, a growing loop you forgot to balance, alcohol in pot ale or spent lees.
• Wash strength down → fermentation (yeast, temperature, infection, short ferments) or mashing (extract recovery, milling, temperatures).
• PSY itself down → the malt changed; talk to the maltster, and reset expectations before blaming the stillhouse.
• Everything fine except the number → measurement. Receiver dips, hydrometers, temperature corrections and tank calibrations drift too.

Where yield tracking goes wrong

1. Ignoring the loop. Quoting yield without the LWFR opening/closing balance makes every period a lottery.
2. Per-run yields treated as truth. Individual runs vary with charge composition; only period yields with charge balances mean anything.
3. Mixed units. Bulk litres at one temperature, strengths at another, LPA computed inconsistently. Pick the convention; correct for temperature; write it down.
4. No tie to the malt certificate.Without PSY on record, "actual vs predicted" — the most diagnostic ratio — can't be computed.
5. Samples and losses unrecorded.Small individually, but they are the gap that makes the mass balance "not quite close" forever.
6. Yield lives in the stillman's notebook. Fine until the stillman is on holiday during the bad month.

And one compliance note: this same stillhouse record — charges, receipts, loop stocks, losses — is what sits behind your production figures when spirit is filled to cask and enters the warehouse bookkeeping that feeds the W1. Yield tracking and compliance are the same records wearing different hats.

How Provenate tracks yield

Provenate is distillery management software that records the whole chain as one connected thread:

• Mash to cask, linked. Each mash records its malt (and PSY), its washbacks record wash strength, and distillations record charges, foreshots/heart/feints splits and receiver output — alcohol treated as a conserved quantity at every step.
• The loop balanced for you. Low wines and feints stocks are carried per period, so period yields come with the charge balance already applied.
• Yield vs PSY per mash, per period, per season — with drifts visible on the production graphs instead of discovered at year-end.
• Same records, two purposes. The production thread flows into cask filling and the warehouse accounts, so operations and compliance stop being parallel spreadsheets.

Want to see your yield with the loop balanced automatically? Book a demo.

Official sources

• Alcoholic products technical guide
• The Scotch Whisky Regulations 2009