> ## Documentation Index
> Fetch the complete documentation index at: https://brewgravity.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Fermentation

> Logging readings and reading the curve.

The Fermentation tab is a running record of what the beer did after you pitched:
gravity, temperature, pH, volume, and whatever you want to write down. It is the
part of Brewgravity you will open most often, usually on a phone, usually standing
next to a fermenter.

## Adding a reading

A reading needs whatever you actually measured — nothing is required, and there
is no such thing as an incomplete entry:

**Brewgravity** `SG, °P, or Brix`

Enter it in whichever unit your instrument reads in. Brewgravity converts to
specific gravity for storage but remembers the unit you typed, so a Plato
reading still displays as Plato.

**Temperature** `°C or °F`

Beer temperature, not ambient — the difference during active fermentation is
frequently several degrees and always in the direction you did not want.

**pH** `0–14`

Optional, and mostly interesting if you are chasing a specific finish or
working with mixed cultures.

**Volume** `litres or gallons`

Useful when you rack, take samples, or account for trub loss.

**Notes** `text`

Krausen fell, dry hops in, moved to the garage, smells like bananas.

> [!TIP]
>
> Refractometer readings on fermenting beer are wrong unless corrected —
> alcohol skews the refractive index. Choose the **Brix (Refract.)** unit and
> Brewgravity applies the correction using the batch's original gravity, rather than
> handing you a number that says the beer stopped fermenting on day three.

## Reading the chart

Readings plot as a gravity curve over time. The two milestones — your OG when
you started fermentation, and your FG when you completed it — are marked on the
curve automatically, so the chart always has its endpoints.

What the shape tells you:

> **A steep drop then a flattening**
>
> Normal and healthy. Most of the attenuation happens in the first 48–72
> hours; the tail is the yeast cleaning up.

> **A flat line well above expected FG**
>
> A stuck fermentation. Usually temperature, underpitching, or a mash that
> left too much unfermentable sugar. Two readings 24 hours apart that agree
> are the actual test — one reading is never enough to call it.

> **A curve that keeps creeping down**
>
> Something is eating what the primary yeast could not. Fine if you meant it
> with a Brett or mixed culture, worth investigating if you did not.

## Finishing up

When gravity is stable, enter your final gravity and press **Complete**.
Brewgravity records the FG, stamps the completion time, and the session summary
gives you the numbers that matter for next time:

| Number | Why it matters |
| - | - |
| **Measured ABV** | From your real OG and FG, not the recipe's estimate |
| **Apparent attenuation** | How this yeast actually performed on your system |
| **Days fermenting** | How long it really took, versus what you planned |

Those three numbers are the reason to log at all. The next time you brew this
recipe, they are what you plan against.


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