General Homebrew Information
I'll be adding general info, hints and tips about home brewing on this page, as I find time to write them. The first one is about Water Treatment, and the simple way in which I treat my soft water to make it suitable for brewing. The second is about the Bitterness to Gravity Unit Ratio, which you need to know about if you have the details of a beer which you like but you want to make a stronger or weaker version.
Water Treatment
You can brew beer with just about any water, but it's preferable that you have certain minerals in your water within a given range. The main things that matter in brewing are the amount of calcium, sodium, sulphate, magnesium, chloride and carbonate in the water. If you are going to ask your water company about the water analysis for your area, some people suggest asking about the hardness, pH and Iron as well.
Most water in the UK will make acceptable beer, but it doesn't take much to make it better. The worst thing about some UK water is the chlorination, which in certain cases can produce a 'phenolic' taste to your beer. Luckily, I don't have that problem.
It doesn't take much searching on the internet to find typical water analysis for various classic brewing areas of the world, and if you are trying to make a certain style of beer you can try to emulate the water of that area. I used to try to do that, but now I just treat my water so that it is suitable for brewing.
The following values for optimum mineral concentrations in brewing water comes from an article in Zymurgy magazine Vol. 18 No. 4 Special 1995, 'The Great Grain Issue':
Calcium (Ca) between 50 and 150ppm
Sodium (Na) between 70 and 150ppm
Sulphate (sulfate) (SO4) less than 400ppm
Mangnesium (Mg) between 10 and 20ppm (must be less than 30)
Chloride (Cl) less than 250ppm (this should ideally less than 100ppm for light beers)
Carbonate (HCO3) ideally less than 50ppm for pale beers
The water where I live in Exeter is very soft. Fortunately it is very easy to modify a soft water to make it suitable for brewing the sort of beer that I want to drink, using the commonly obtained ingredients of gypsum (available from any homebrew shop), epsom salts (from a chemist) and common salt. Don't use ordinary table salt, as it usually has anti-caking agents added such as magnesium carbonate, sodium hexacyanoferrate and even (in the USA) iodine. I use sea salt, from a health shop.
Back in 1999 I wrote to my local water company asking for typical values for Exeter's water. The answer I got from them gave the following information:
Calcium 23 mg/l
Sodium 10 mg/l
Sulphate 26 mg/l
Magnesium 4 mg/l
Chloride 17 mg/l
Carbonate 55 mg/l
[mg/l is the same as ppm, or at least as far as we are concerned it is]
You can see that I need to increase the amount of Calcium, Sodium and Magnesium in my brewing water to bring it into the right sort of range. My carbonate is possibly a little too high, but not significantly. Everything else is OK.
The chemistry calculations are very simple if you can remember Moles from your school chemistry lessons, but in case you can't here are the figures for gypsum, epsom salts and common salt:
For water treatment, the addition of 1 gram increases the ppm of 1 litre of water by the following amounts -
Gypsum - 230ppm Ca
Gypsum - 560ppm SO4
Epsom salts - 100ppm Mg
Epsom salts - 390ppm SO4
Salt - 400ppm Na
Salt - 600ppm Cl
So, if you're adding to 23 litres of water, the addition of 1 gram of gypsum increases Ca by 230/23 = 10ppm and SO4 by 560/23 = 24ppm etc. With my water I need to do the following:
Increase -
Calcium by between 27 and 127ppm
Sodium by between 60 and 140ppm
Mangnesium by between 6 and 16ppm
In doing so I don't want to increase -
Sulphate by more than 374ppm
Chloride by more than 233ppm and ideally by no more than 83ppm
Carbonate by anything
Let's start with the magnesium. I get that from epsom salts and I want to increase it by about 10ppm. 1 gram of epsom salts increases the magnesium in each litre by 100ppm, so I need to add 10/100 = 0.1 grams for each litre that I am treating. This will also increase my sulphate by 390 x 0.1 = 39ppm so my sulphate level will now be 26+39= 65ppm.
Now let's add some gypsum to get the calcium level up. I need to increase the calcium by about 60ppm so I need to add 60/230 = 0.26 grams of gypsum. This will also increase my sulphate by 560 x 0.26 = 145ppm, so now my sulphates are 26 + 39 + 145 = 210ppm - still OK.
Finally, we need to increase the sodium level without increasing the chloride too much. Trying an increase of 60ppm, we add 60/400 = 0.15 grams of salt, which also increases the chloride by 600 x 0.15 = 90ppm. This puts the chloride at 107ppm - just a little over the optimum levels for light beers, but as I don't make many light beers anyway this is still OK.
So, the final mineral content of our water is -
Calcium 83 mg/l
Sodium 70 mg/l
Sulphate 210 mg/l
Magnesium 14 mg/l
Chloride 107 mg/l
Carbonate 55 mg/l
Now, the last thing to do is to convert these fractions of grams per litre into something more practical. I tend to make my beer in 5 imperial gallon (23 litre) batches, so I'm treating 23 litres at a time.
So I want to add -
23 x 0.1 = 2.3 grams of epsom salts
23 x 0.26 = 5.98 grams of gypsum
23 x 0.15 = 3.45 grams of salt
There's no need to be silly with the 1/100ths of grams - what I did was use a set of kitchen 'teaspoon' measuring spoons and measure out 10 measures of each item, weighed what I'd got and divided the total by ten to get a weight for each teaspoonful. After a few trials, I found that suitable values are given by adding the following amounts to each 23 litres of water that I am treating:
2 slightly rounded teaspoons of gypsum
1 rounded half teaspoon of salt
1 half teaspoon of epsom salts
And that's how I treat my water for brewing.
Bitterness to Gravity Units Ratio
If you look at my recipes you'll notice that there are some where I've modified the strength of a beer which I like but which may be too strong for me. If you, too have a recipe for beer which you want to make and would like to change the strength of it, then you need to change the bitterness as well, to match. There is a simple way of doing this which works well, which involves maintaining the "Bitterness to Gravity Units Ratio".
Bitterness Units are also known as IBUs or 'International Bitterness Units'. Gravity Units are just the last two digits of the Original Gravity of a beer, so if a beer has an Original Gravity of 1055 then it has 55 Gravity Units. If you want a mathematical formula it's simply GU=(OG-1000).
The Bitterness to Gravity Units Ratio is simply the first number divided by the second and if you change the strength of a beer then you need to change the bitterness in order to maintain the same ratio that it originally had. If, for example, the original beer was 1068 with an IBU of 44 then it has a Bitterness to Gravity Units Ratio of 44/68. If you want to reduce the gravity to 1058, then you simply need to reduce the bitterness to keep the same ratio - i.e. to 58x44/68 = 37.5