Parti-gyle brewing is a very old method of brewing and is a great technique for making several distinct beers from one mash. It works by performing one mash, draining it and then performing a second mash with the same grain and draining that before boiling each wort separately with your various hop additions. The first wort is most likely a smaller volume but higher gravity wort whereas the second wort is likely to be a lower starting gravity but a higher volume. The joy of boiling each wort separately means that you can change hop schedules and boil additions and after chilling you can use different yeasts, fermenter additions, and dry hops to make very distinct beers. You may even choose to do three or four ‘gyles’ so you end up with several very distinct beers for just a little bit more work on brewday. The name for the technique comes from the old name for a full batch of wort which was a ‘gyle’ – so part of a gyle was known as ‘parti-gyle’.

One of my other favourite reasons for doing a parti-gyle brew is that producing a full batch of high ABV barleywine or double IPA or Imperial stout can leave you with a lot of strong beer to get through. With a parti-gyle you can still make your full 23/24 litre batch but you can slit it to give you a small volume of ABV ale and a larger volume of more drinkable ‘small beer’.

Working out your parti-gyle recipe requires a little bit of maths if you want to get it right. This can sound complicated because it’s maths but stick with it because in practicality it’s easier than it initially seems.

For my most recent parti-gyle I wanted to brew 9 litres (2.4 gallons) of American barleywine and 15 litres (4 gallons) of American Pale Ale. I wanted my barleywine to have an OG of 1.075 and my pale ale to have an OG of 1.035. If you take the gravity units (GU) of each beer and multiply them by the volume in gallons you get;

2.4 x 75 = 180

4 x 35 = 140

Total points = 320

So, next comes the fun part. For my recipe I’m using 4.55kgs of maris otter, 950g of Munich malt and 160g of crystal malt. Using a table off typical malt yields such as this one I can see that 1lb of Maris Otter gives me a maximum points per gallon yield of 1.035 in 1 gallon of water. Munich gives me 1.035 and crystal gives me 34.

Now multiply those yields by your expected efficiency. In my case, 75%. This gives me;

Maris Otter = 26

Munich = 26

Crystal = 25.5

Now, converting my recipe to pounds I want 9.3 lbs of Maris Otter, 2.1 lbs of Munich and 0.4lbs of Crystal. Multiply these amounts by their points per gallon;

10 x 26 = 260

2.1 x 26 = 54.6

0.4 x 25.5 = 10.2

Total = 325

And that’s the total points I can expect to get from my grain bill. Now, if I miss my gravity’s on brewday I can use the gravity units principle to adjust by either diluting my wort or extending the boil in order to concentrate my wort. This is a concept that we’ve covered in greater detail in this blog post

Be aware that if you do make adjustments to your wort volume on the day you are also going to need to adjust your hop additions to ensure your bitterness remains balanced.

There will be a parti-gyle brewing video coming up in the next few weeks so don’t worry if you found this a little confusing, we’ll be showing you exactly how easy this can be.

As always, if you have any questions or comments let us know in the comments section below or by emailing [email protected]

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