The next thing we want to answer is how much brewing liquor do you use in mashing?
Previously we have looked at how we calculate the grist recipe both for a very simple ale and a more complicated ale. If you have not read these articles they can be accessed here. The next question that is worth answering is how to calculate the amount of brewing liquor required in the mash and therefore how much liquor will be available for sparging. Once again as for the grist recipe the solution to this problem is fairly straight forward and involves something called the grist to liquor ratio.
What is the grist to liquor ratio?
The grist to liquor ratio is, as the title suggests, the ratio of brewing liquor to grist. It is usually expressed as a number for example 3:1 and it is important to remember that, despite what the title suggests, the first number refers to the brewing liquor and not to the grist. Therefore if you want to call it the liquor to grist ratio then please go ahead. Therefore if we use the example above of a liquor to grist ratio of 3:1 then if we have 5 kg of malt we will require 15 litres of brewing liquor that is required in the mash vessel.
The next question we need to answer is how do we decide on what liquor to grist ratio to employ? The simple answer is that it is entirely up to you as the brewer. I have seen liquor to grist ratios as low as 2:1 (very thick mash) up to as high as 4:1 (very thin mash). For example if we return to our example above of a 5 kg grist charge a 2:1 liquor to grist would give us 10 litres of brewing liquor. Contrast this with the requirement of 20 litres of brewing liquor in a 4:1 mash and you can see there is quite a difference. In reality the typical working range for liquor to grist ratio is 2.5:1 up to 3.2:1 but are there any advantages to employing a thicker or thinner mash?
It can generally be stated that the liquor to grist ratio is chosen based on upon the mashing process you are using. For example a single temperature infusion mash can generally tolerate lower liquor to grist ratios. Whereas if you are using a lauter tun or employing a decoction mash then a thinner mash is employed as the mash is easier to pump.
However, there are other reasons why you might chose thicker or thinner liquor to grist ratios. If you are brewing a high gravity beer it is generally easier to use a thicker mash to achieve the higher target OG. There is some evidence that brewing enzymes, in particular beta amylase, are more stable in a thicker mash with the suggestion that by preserving the beta amylase you produce more fermentable worts. In practice I have never been able to prove this phenomenon and I would suggest mash pH and the presence of Calcium ions has a far greater effect on beta amylase activity than mash thickness. I would therefore not worry about using a thicker mash for this reason alone. For me the most practical reason for selecting one particular liquor to grist ratio over another is wort filtration. I have encountered issues with wort run-off where the liquor to grist ratio has just been too thick. It has never been a critical issue but run-off tends to be slower with low liquor to grist ratios and thick mashes. The ultimate test is how the liquor to grist ratio works on your mashing system and the key is to experiment and give it a go. I tend to use a 3:1 liquor to grist ratio first and then if I encounter no problems go a fraction lower on the liquor to grist ratio.
Now that we have covered liquor to grist ratio it is worth taking our worked example where we wish to brew 25 litres of a 5% abv ale type beer. We have already calculated our grist recipe which is:
Ale Malt = 3.9 kg
Torrefied Wheat = 0.5 kg
Crystal Malt = 0.25 kg
This gives us a total grist charge of 4.65 kg. If we select a liquor to grist ratio of 3:1 we then multiply the 4.65 kg grist charge by 3 to calculate the volume of brewing liquor that we require.
Brewing Liquor = 4.65 x 3
Brewing Liquor = 13.95 Litres
For ease we can round this up and therefore use 14 litres for our mashing.
If we change the liquor to grist ratio to 2.5:1 the volume of brewing liquor changes:
Brewing Liquor = 4.65 x 2.5
Brewing Liquor = 11.62 Litres
Once again for ease we can round that up to 12 litres.
There you have it a simple way to calculate how much brewing liquor do you use in mashing.
In our next article we will take a look at the complex field of beer colour and how you can calculate beer colour.