Two Beers From One Mash

Last weekend I brewed my attempt at the International Homebrew Project Burton Ale.

After last year’s very strong mild left me feeling I’d missed a trick, this time I prepared myself for brewing two beers from the one mash.

Here’s how I planned it, and what actually happened.

two beers from one mash

Getting more than one beer from a single set of grains is not new.

One way of doing it is with parti-gyle. That’s an old brewing technique that yields several beers from one mash.

Fullers still use it to produce the family of beers that includes London Pride and Chiswick Bitter.

As far as I can gather, parti-gyle brewing specifically involves blending the beers after boiling.

The quality of the wort reduces with each rinse, and blending helps smooth out blemishes. Apart from that, as I’ve found out, controlling the gravities in completely separate worts is difficult.

But more on that later.

Parti-gyle seems to have been picked up by home brewers as a general term meaning “more than one beer from the same grains” but I think what I’m about to explain, without blending, is combined grist brewing.

I had the idea last year but it’s taken me this long to organise it. Mainly because as a brew in the bag brewer I’ve been wondering how practical it is.

BIAB Combined Grist Brewing

The Burton Ale recipe, set by Alistair at Fuggled, for this year’s Homebrew Project is simple:

100% pale ale malt
(O.G. 1.079)

83 IBUs Cluster for 90 mins
42 IBUs Kent Goldings for 30 mins

It’s based on an 1877 Truman No. 4 recipe, which was brewed in the company’s brewery in Burton.

This is the first beer from the combined grist.

To make life easier, I decided to take advantage of the way my brew process already works.

There’s a natural break between two different worts: the one that’s left in the brew pot when I remove the brew bag (the first runnings), and the one that slowly drains from the bag (the second runnings).

Normally I mix the two before boiling, but for the combined grist experiment I maintained the separation.

The first runnings would make the Burton Ale, with the rest going on to become the second beer.

Because I’ve been recording gravity and volume in detail, I was able to make some guesses about how the two beers would pan out.

Planning The First Beer

When I remove the brew bag from the pot, on average 2/3 of the starting volume of water stays behind, and it contains 2/3 of the total gravity points.

With 4.55 kg pale ale in stock, I planned the brew around that. Slightly random but you have to start somewhere.

Although I expected a higher efficiency than usual from the extra rinsing, I stuck with 70% for planning purposes.

This meant I would have 978 total gravity points to split between the two beers.

(I’m not going to explain the calculations in detail – read this if you can’t follow along)

Using 2/3 of those points, I worked out the starting water volume and hop additions for the Burton Ale.

Planning The Second Beer

For the second brew I didn’t want a random beer, but something related to the Burton Ale.

Browsing through Let’s Brew on Shut Up About Barclay Perkins I found another Truman’s beer, also from Burton, with the same grain bill.

(It sounds like all the Truman’s beers from Burton at the time were 100% pale malt).

It’s a strong export pale ale from 1883, so only 6 years after the No. 4 was brewed. The original gravity is 1.069.

The selling point was the unusual hop schedule, with hops from four different countries.

Not only was it intriguing, it happened to coincide with the contents of my leftover hop tub.

Knowing roughly how many gravity points would be left in the second wort, I could settle on a target volume and work out the hop additions for the second beer.

Two Beers From One Mash: The Recipe

I ended up with this recipe plan:


100% Pale ale malt: 4.55kg
Starting Volume: 17.1 litres
Efficiency 70%

First Beer: Burton Ale

Assumed that first runnings are made of:
67% post-grain water
67% gravity points

8.3 litres expected volume

Equivalent to:
100% Pale ale malt

83 IBUs Cascade (6%): 43g pellets for 90 mins
42 IBUs Kent Goldings (4%): 45g pellets for 30 mins


Second Beer: Export Pale Ale

Assumed that second runnings are made of:
33% gravity points
Extra water added: 9.8 litres
Expected volume: 4.7 litres

Equivalent to:
100% Pale ale malt

41 IBUs Cascade (6%): 9g pellets for 180 mins
40 IBUs Styrian Goldings (4.4%): 13g pellets for 120 mins
14 IBUs Hallertauer (4.8%): 9g pellets for 15 mins
14 IBUs Saaz (4.2%): 10g pellets for 15 mins


Because the second beer is almost as strong as the first, I only expected about a litre more beer out of the technique than I would have got normally.

I hope you can see though, that with another 5-10 litres of water you’d get a lot more of a weaker beer. And the idea of getting two different beers from one brew day is pretty good in itself.

Brewing Two Beers From One Mash

The brew went fairly well. I did get two beers out of it, even though my “predictions” didn’t come true.

It started OK. The volume and gravity of the first runnings were very close to expected. The gravity points were a little short, that’s all.

two beers from one mash BIAB first runnings

It was so close I left the hop additions as planned.

Unfortunately the small batch size seemed to increase the evaporation rate to a lot more than I’d expected. After 90 minutes I was down to just 6 litres of beer.

By strange chance, this brought the gravity back up close to target and I finished with an original gravity of 1.081, just 2 points over.

The shortfall in beer forced my hand and I decided to lower the target gravity of the second beer.

This, along with the “missing” gravity points from the Burton Ale, let me increase the volume of the pale ale.

After a rough calculation based on what I knew, I heated 15 litres of water in the brew pot to 55°C and added back the grain bag.

two beers from one mash brew in a bag second runnings

When the water had reached 70°C I removed it and drained as usual.

To cut a long story short I finished up with 11 litres of beer at 1.050.


For what it’s worth, here’s what I brewed:


100% Pale ale malt: 4.55kg
Starting Volume: 17.1 litres
Efficiency (in fermenter): 75%

First Beer: Burton Ale

“First runnings”:
67% post-grain water
47% gravity points
6 litres final volume

100% Pale ale malt

83 IBUs Cascade (6%): 43g pellets for 90 mins
42 IBUs Kent Goldings (4%): 45g pellets for 30 mins


Second Beer: Export Pale Ale

“Second runnings”:
53% gravity points
Extra water added: 15 litres
Final volume: 11 litres

100% Pale ale malt

41 IBUs Cascade (6%): 21g pellets for 180 mins
40 IBUs Styrian Goldings (4.4%): 28g pellets for 120 mins
14 IBUs Hallertauer (4.8%): 19g pellets for 15 mins
14 IBUs Saaz (4.2%): 22g pellets for 15 mins


If that’s of use to you great. But I suspect this requires more than one brew before any conclusions are drawn.

Testing the method is what this was for, and I’d say it worked.

I developed it from first principals, so apologies if there’s a more refined version out there I don’t know about. As I said, I wanted to work as much as possible with my current brew day routine.

It was a totally idiosyncratic brew based around my two fermenters (6 and 20 litres), the amount of pale ale malt I happened to have left, and my participation in the International Homebrew Project.

I just couldn’t resist trying the two Truman’s Burton beers together.

In a way it’s completely over the top to make so much effort for a few more litres of beer. On the other hand it was great fun!


In the spirit of making the most of the malt, I finished up by making a plum cake with the spent grain.

plum cake made with spent home brew grains

Very nice it was too.

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  1. Hi!
    I hope you are well! I wanted to comment below a different section of your site, but couldn’t find a space to do so. I want to thank you so much for your site! It has been such a great resource as a beginning brewer! I followed your advice and have only ever used all-grain and BIAB. I love the process!

    I wanted to mention that I use your frozen bottles technique for cooling the wort. However, I now put the bottles in the bucket filled with StarSan solution, then directly into the brew kettle to cool the wort. It works great! The wort is cooled to 20C in 15-20 minutes (depending on volume). I have had no issues with any sort of contamination. It’s a great time-saver.

    Best and Cheers! ~Antonio

    • John

      Hi Antonio,

      Thanks for the tip.

      I recently tried adding ice straight to the wort (outside the bottle) but found it melted almost immediately and didn’t cool it quickly enough.

      Perhaps I’ll try your method as it sounds good.