Mash water and mash temperature
How much water to add and to what temperature to heat it.
Mashing begins with water. Its volume sets the water-to-grain ratio — which determines mash density and how completely saccharification proceeds — and the strike water must be hotter than the target: part of the heat goes into heating the grain and the vessel.
Calculator
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Water-to-grain ratio
The water-to-grain ratio is the ratio of water to malt: 3 litres per kilogram means that 5 kg of malt needs 15 litres of water. A thin mash (3.5–4 L/kg) heats more evenly and gives slightly more complete saccharification; a thick one (2.5 L/kg) is faster and better suited to brewing with sparging.
A mash that is too thick (below 2.5 L/kg) slows the enzymes and increases the risk of scorching; one that is too thin dilutes the enzymes and lengthens the boil.
Strike water temperature
Room-temperature malt and a cold vessel will take up part of the heat, so the water must be hotter than the target mash temperature. The classic estimate is John Palmer’s formula: the correction is inversely proportional to the water-to-grain ratio.
Twater = (0.41 / R) · (Ttarget − Tgrain) + Ttarget where R is the water-to-grain ratio, L/kg
Temperature rests
| Rest | Temperature |
|---|---|
| Beta-glucan | 40–45 °C |
| Protein | 50–55 °C |
| Maltose | 62–64 °C |
| Saccharification | 66–68 °C |
| Mash-out | 75–78 °C |
What to keep in mind
- Measure the grain temperature instead of assuming “20 °C”: in winter the sack sits in a cold room.
- The 0.41 coefficient assumes a typical mash tun. A thick-walled vessel or preheating will shift the result.
- For step mashing, take part of the mash, bring it to a boil and return it.
- Saccharification also depends on the crush and the quality of the malt: the calculator works out water, not enzymes.