Whether it happens in a gleaming commercial brewhouse or a garage with a big pot, the brew day follows the same essential path. Grain becomes sweet liquid, that liquid is boiled with hops, then cooled and handed over to the yeast. Here is how it works.
The Big Picture
| Stage | What Happens | Typical Time | Key Target |
|---|---|---|---|
| Mill | Crack the grain | 10–20 min | Crushed kernels, intact husks |
| Mash | Soak grain in hot water | 60–90 min | ~62–70 °C, pH 5.2–5.6 |
| Lauter | Separate sweet wort from grain | 30–90 min | Clear wort, good efficiency |
| Boil | Boil wort with hops | 60–90 min | Rolling boil, hop additions |
| Chill | Cool wort rapidly | 15–45 min | Pitching temperature |
| Pitch | Add yeast | 5 min | Healthy yeast, aerated wort |
1. Mill
Malt must be cracked so water can reach the starchy interior. The goal is to break the kernel into pieces while keeping the husk mostly whole, because the husks form the filter bed later.
- Too coarse — poor sugar extraction
- Too fine — a gummy mash that clogs, known as a “stuck sparge”
Many homebrew shops will mill grain for you.
2. Mash
The crushed grain is mixed with hot water — this is called mashing in — and held at a steady temperature. Enzymes in the malt convert starches into sugars:
- Beta-amylase (most active around 55–65 °C) makes highly fermentable sugars → drier beer
- Alpha-amylase (most active around 68–72 °C) makes longer, less fermentable sugars → fuller body
Most brewers pick a single rest in the middle, around 65–67 °C, for a balanced result. Some styles use step mashes or traditional decoction mashing, where part of the mash is boiled and returned to raise the temperature.
At the end, some brewers perform a mash-out at about 76 °C to halt enzyme activity and make the wort flow more easily.
3. Lauter
Lautering separates the sweet liquid, now called wort, from the spent grain.
- Vorlauf — Recirculate the first cloudy runnings back over the grain bed until they run clear.
- Run off — Drain the wort into the kettle.
- Sparge — Rinse the grain with hot water (about 75–78 °C) to collect remaining sugars.
Common sparging methods:
- Fly sparging — continuous rinsing while draining
- Batch sparging — drain, add water, stir, drain again
- No-sparge / Brew-in-a-Bag (BIAB) — the whole volume is mashed at once and the grain bag is lifted out
Do not over-sparge: rinsing too much or with overly hot water can extract harsh, astringent tannins.
4. Boil
Bring the wort to a vigorous, rolling boil, usually for 60 minutes (90 for some Pilsner-malt beers). The boil:
- Isomerises hop alpha acids for bitterness
- Sterilises the wort
- Drives off DMS, a compound that smells like cooked corn
- Coagulates proteins into the “hot break,” improving clarity
- Concentrates the wort through evaporation
Watch for boil-overs as foam builds just before the boil breaks — keep a spray bottle of water handy. Hop additions follow the recipe schedule, and finings like Irish moss or Whirlfloc often go in during the final 10–15 minutes.
5. Chill
Once the boil ends, cool the wort as quickly as possible to yeast-friendly temperatures — roughly 18–20 °C for most ales, cooler for lagers. Fast chilling:
- Reduces the window for contamination
- Limits DMS formation
- Creates a “cold break” of proteins for clearer beer
Common tools include an immersion chiller (copper or stainless coil with cold water running through), a counterflow or plate chiller, or for small batches, an ice bath in the sink.
6. Pitch
From this point on, everything touching the wort must be sanitised. Transfer the cooled wort to a clean fermenter, leaving most of the sediment (trub) behind. Then:
- Take a gravity reading with a hydrometer or refractometer
- Aerate by shaking, splashing or using an oxygen stone — yeast needs oxygen now, though not later
- Pitch the yeast
- Seal with an airlock and move to a temperature-controlled spot
Within 12–48 hours you should see signs of fermentation.
Brew-Day Safety
- Hot liquids and heavy pots are the biggest hazard. Lift carefully, use proper burners outdoors if using propane, and keep children and pets away.
- Ventilate if using gas burners indoors — carbon monoxide is a real risk.
- Use food-safe materials and brewing-specific sanitisers as directed.
- Check that homebrewing is legal where you live, and remember that you may ferment, but never distill, at home.
Clean as You Go
Rinse equipment immediately after use while residue is still soft. A tidy brew day is a safer, shorter and more pleasant one — and a clean brewery makes clean beer.