Four batches that went wrong, and what each one cost
A log that records only the good batches is a scrapbook. These four are the entries I go back to, because each of them exposed a habit that had been quietly wrong for months before the beer finally complained about it.
| Brewed | 9 November 2025 |
|---|---|
| Written up | 25 January 2026 |
| Into the fermenter | 19 litres |
| Mash held at | 65 °C for 60 min |
| Cellar on the day | 11 °C |
| Original gravity | 1.052 |
| Final gravity | 1.010 |
| Strength | 5.5 % by volume |
FG 1.010OG 1.052
Read with a hydrometer at twenty degrees, at the kitchen table, before anything got washed.
01 / 04
The sour summer ale and the tap in three pieces
July 2023, a plain pale ale, twenty litres. It smelled right going into the fermenter, and by the fifth day there was a thin white film across the surface and a smell underneath the hops that I can only describe as damp cardboard turning towards vinegar. I gave it another week in the hope of being wrong about it. Tasting settled the question: sharp, hollow and unmistakably not beer. The lot went onto the compost heap at the allotment and the fermenter went into hot caustic overnight.
The cause was almost certainly the fermenter tap, which I had been rinsing in place for two years without once taking apart. The seat behind the plastic washer had never met sanitiser, and by the third summer there was enough living in there to beat a healthy pitch of yeast on its own ground. Anything that touches cooled wort now comes apart before it is cleaned, and the tap has a line of its own on the checklist. Losing twenty litres to four minutes of laziness is a particular kind of annoying.
02 / 04
A stuck sparge and six kilograms of flour
The stuck sparge came out of being pleased with myself about the mill. I had tightened the gap to squeeze a little more sugar out of the western barley, and what came through was closer to flour than to crushed grain. The mash set like wet cement in the cool box, the runnings slowed to a trickle and then to nothing, and I spent forty minutes stirring, waiting and finally bailing the whole bed into the kettle with a jug. The beer was fine. The brew day ran to six hours.
Husk is what makes a grain bed work: the crush has to split the kernel and leave the husk more or less whole to hold the filter open. The mill gap is checked against a feeler gauge before every brew now, and a handful of the crush gets rubbed between my palms to see whether the husks are still in pieces I can recognise. An extra two per cent of sugar is not worth a bed that will not run, and on a hob-limited day it is certainly not worth the hour.
Off the card
- Mill gap checked with a feeler gauge, not from memory
- Husks intact enough to recognise between the fingers
- A handful of rice hulls whenever the bill is heavy in wheat
- Sparge slowly; a fast run compacts the bed and stalls it
03 / 04
The ferment that stopped half way
A strong dark beer in April 2024 reached half its expected attenuation and sat there for nine days. The readings were flat, the airlock silent, the sample sweet and faintly cloying. I had pitched one sachet of yeast into a wort thick enough to want two, in a cellar reading eleven degrees, and then wrapped the fermenter in a blanket and congratulated myself on the insulation. Underpitched, short of oxygen and too cold: any one of those on its own would probably have been survivable.
It restarted after four days upstairs in the wardrobe with a fresh, well-fed pitch swirled into it, and finished roughly where it should have. The beer came out sweeter than planned and nobody complained about that. The lesson was arithmetic rather than technique. A big beer needs more yeast, more oxygen and more warmth than a small one, and how much more is not something you can feel your way to. The target gravity now goes on the card first, the night before, and the pitch is worked out from it on paper.
04 / 04
Bottles that went off in the cellar
In December 2022 a crate of wheat beer began to hiss when opened and then to foam out of the neck for a full minute. Two of them let go on the cellar shelf overnight, which is a mess you clean up once before you start taking the problem seriously. The gravity had not been stable when I bottled it. I had bottled to a calendar instead — twelve days, because the previous three batches had happened to finish in twelve days.
Residual sugar, plus priming sugar, plus a cellar that warmed through the spring, made rather more carbon dioxide than the glass was built to hold. Two rules came out of that crate and neither has been broken since. Bottling waits for two matching gravity readings taken two days apart, and the first bottle of any batch is opened over a sink on day ten as a test. A bottle that gushes at day ten is a batch that goes straight back into the cold.
Off the card
- Two matching gravity readings, two days apart, before bottling
- Priming sugar weighed for the volume, never scooped
- One test bottle opened over the sink on day ten
- Crates kept low and covered, out of the spring warmth