Temperature is important value through all brewing process, so it is common that we talk about temperature here.
We will learn here how to calculate strike water temperature or if we are mashing with more rests we will also learn how much water to add and at what temperature.
Tiw (temperature of the infusion water) Units: °C or °F
Vt (amount of water in the mash) Units: L or qt
Vb (amount of boiling water added) Units: L or qt
Ti (initial mash temperature – or initial grain temperature) Units: °C or °F
Tt (target mash temperature) Units: °C or °F
m (weight of grain in the mash) Units: kg or lb
MT (mash thickness – ratio water to grain) Units: L/kg or qt/lb
Equations for US units:
Tiw = (0,2/MT) x (Tt – Ti) + Tt
Vb = (Tt – Ti) x (0,2 x m + Vt)/(Tiw – Tt)
…for metric units:
Tiw = (0,41/MT) x (Tt – Ti) + Tt
Vb = (Tt – Ti) x (0,41 x m + Vt)/(Tiw – Tt)
Example recipe: At brewing we will use Pale Ale malt (4,42 kg/9,75 lb), Roasted Barley malt (0,19 kg/0,41 lb), Biscuit malt (0,42 kg/0,93 lb) and Chocolate malt (0,11 kg/0,24 lb).
If we will use only one rest, we need to use only first equation, so we only need to calculate temperature of infusion water (Step 1). But if we will use more rests we must use both equations (Step 1 and Step 2).
Step 1: Calculate temperature of the infusion water (you can calculate volume of strike water with help of water volumes calculations on this site). We can calculate using US or metric values (some values may deffer becouse of approximate conversion from metric to US values, but those differences are very small). Target temperature of infusion water (Tiw) is 67 °C/152,6 °F, we decided for mash thickness (MT) 3,1 L/kg / 1,5 qt/lb, initial grain temperature is 22 °C/ 71,6°F.
Tiw = (0,2/MT) x (Tt – Ti) + Tt = (0,2/1,5 qt/lb) x (152,6 °F – 71,6 °F) + 152,6 °F =
Tiw = 163,4 °F
Tiw = (0,41/MT) x (Tt – Ti) + Tt = (0,41/3,1 L/kg) x (67 °C – 22 °C) + 67 °C =
Tiw = 73 °C
If we are using one rest, we can stop here. But if we are using multi rest mashing, we can go on to Step 2.
Step 2: Calculate volume of boiling water that we will add to achive wanted mash temperature.
Let’s say that we have made first rest at temperature of 60 °C/140 °F (Ti) and we want to make second rest at 70 °C / 158 °F (Tt). Boiling water that we will add has 100 °C / 212 °F (Tiw). We mash 5,14 kg / 11,33 lb of malt (m) in 16 L/16,9 qt of water (Vt)
Vb = (Tt – Ti) x (0,2 x m + Vt)/(Tiw – Tt) = (158 °F – 140 °F) x (0,2 x 11,33 lb + 16,9 qt)/(212 °F – 158 °F) =
Vb = 6,4 qt
Vb = (Tt – Ti) x (0,2 x m + Vt)/(Tiw – Tt) = (70 °C – 60 °C) x (0,41 x 5,14 kg + 16 L)/(100 °C – 70 °C) =
Vb = 6 L
Of course we can rise the temperature of mash using direct heating. For that way we do not need those calculations above.
So, we learned some calculations about temperatures!