When you first start all grain brewing or partial mash there are all sorts of thing that you need to start worrying about that you might not necessarily need to consider when you brew with kits or extract. Whilst you are a lot more involved and there are more variables to consider for example, water adjustment, water needed, mash volume and mash temperature just to name a couple of things that you need to include in your calculations before you even begin brewing.
When you come to brew your first batch this seems like a whole lot of hassle I know for me I was all over the place trying to figure out what was needed and when I should use it. When you get a few batches under your belt however these thing become second nature, just par for the course.
Strike Water Temperature
When I say strike temperature I am talking about the temperature of the water needed to achieve your desired mash temperature.
Say for example you want to hit a mash temperature of 67°C / 153°F we need to take into account what drop in temperature is going to occur when you add water to the mash tun and then add grain or if there is already water and grain in the tun. There is calculators and software available to calculate this for you, but why not give it a try by hand first.
Single Infusion Mash – Calculating Strike Water Temperature
The most common mash you are going to perform is a single infusion mash that only requires a rest at one temperature. For this type of mash you generally want the grain to sit between 65°C – 68°C (150°F – 155°F) for an hour for proper conversion.
With this in mind you’ll need to calculate the initial temperature we need to bring the strike water up to so that when we add it to the mash tun and add the grain it sits in the correct temperature range, below is the equation you need to use to find what this initial infusion temperature:
If you are using Fahrenheit, Pounds and Quarts then you’ll need to change the constant of 0.41 to 0.2
Strike Water Temperature Tw = (0.41 / R)(T2 – T1) + T2
- Wa = The amount of infusion water to add
- Wm = The total amount of water in the mash
- T1 = The initial mash temperature (temperature of dry grain for initial infusion)
- T2 = The target mash temperature
- Tw = the actual temperature of the infusion water
- G = The amount of grain in the mash
Mash Infusion Equation
To calculate the effect of an addition of water will have on a mash for example to bring the mash temperature up to hit mash out temperature or to perform a multi step mash we need to use the following equation:
Again you’ll need to substitute in 0.2 if you are using Lbs, Fahrenheit and Quarts
Wa = (T2-T1)(0.41G + Wm) / (Tw – T2)
An Example of Calulating Mash Temperature
Ok so with the above equations in mind let’s run through an actual calculation. Let’s say we are brewing a beer where we want the mash to sit at 67°C (152°F) for 60 minutes and then bring up the mash temperature to 74°C (165°F) to mash out. The temperature of our grain is 18°C
Using the initial infusion equation – Strike Water Temperature Tw = (0.41 / R)(T2 – T1) + T2 we would get the following.
(0.41 / 2.5) x (67-18) + 67 = 75°C
So we would need to heat our initial strike water to 75°C to hit our desired mash temperature of 67°C.
Calculating the addition required to raise the temp to mash out
We would then need to calculate how much of an addition of water is needed to hit the mash out temperature of 74°C. We will also assume the mash has cooled a few degrees to 65°C, our grain bill is 4kg and initial mash liquor is 10 litres. If we add recently boiled water that has cooled to 95°C we will need to use the following equation – Wa = (T2-T1)(0.41G + Wm) / (Tw – T2) achieving the following
(75 – 65) x (1.64 + 10) / (95 – 75) = 5.82 litres
So we would add 5.83 litres of 95°C water to take the mash from 65°C to 75°C.
Bear in mind there is software out there that will do all of this for you, but like a lot of the brewing maths I think it’s a good idea to know whats going on before you blindly plug figures into a computer. Doing calculations by hand first of all just gives you that little extra understanding.