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High Gravity (home) Brewing

I’ve recently been having problems recently with brewhouse efficiency, with my usual 70% figure coming out at 66% or less. This has thrown my usual recipes out of kilter and I had no chance of creating anything double/imperial. After months of trying many different things, I noticed poor efficiency when sparging was over in next to no time. Following up on this, I decided to try fine crushed base malt for a couple of recipes to see if it cured the problem. In fact, it cured the problem so much, that instead of getting me back to ~70% BH efficiency, I saw 75% overall with mash efficiency of 85%! This lead me down a path of discovery to high gravity brewing, which ultimately saw me getting 26 litres from a 22 litre batch.

The Principle

This method of brewing allows for larger volumes of final (packaged) product than the fermentation vessel would otherwise allow. Brewers will create a much stronger wort than required and dilute it back to the required ABV at packaging. This is different to the practice of liquoring back, where the OG is made slightly higher than required, then diluted pre-fermentation for consistency between batches. As the dilution in HGB is done post-fermentation there are more factors to consider, such as deaerated water that is free from any contamination, and with a mineral profile to match the required flavour of the final beer.

The amount of dilution needs to be well considered, as too much will make the beer come across as watery. It seems that dilution up to around 30% is possible without too much effect on the final product. As I was going in to this without HGB in mind, I didn’t have any idea of how much I’d need to dilute, and hoped it wouldn’t need more than around 20%.

The Recipe

I’ve been playing around with some ideas for a Belgian Pale Ale, wanting something Belgian-style I can have from the keg any day of the week. I settled on a 5.4% simple recipe, comprising fine crushed Golden Promise (I didn’t have Pilsner available), CaraMunich and crystal 100. I also had some flavourful Continental hops that I’d been waiting for the right recipe to try, Ariana and T45 Monroe. Yeast was M41 Belgian Ale from Mangrove Jacks.

I was looking for a more red berry/stone fruit flavour from the hops, and was interested to use T45 pellets for the first time. Given the flavour characteristics of both hops, I thought Monroe and Ariana would work well together for this, with all additions going in at 20 minutes or less for an IBU of 28 and a BU:GU around 0.55.

With the mash started and all dough balls taken care of (fine crush very susceptible) I prepared the sparge water and waited the first hour. During the mash I heard the recirc pump change note – something that alerted me to the fact the flow through the mash was too low, and the bed had now compressed. I gave it a stir and reset it, and better matched the to flow rates through to mash out. I’ve also started using a thicker mash than I did previously, so that I can have maximum sparge water to help drive up the efficiency.

The sparge itself was much slower than previous batches, exactly what I was hoping would happen. With boil volume achieved, I took a gravity reading with the refractometer showing 1.053, a full 7 points over the recipe’s 1.046 prediction. This was based on the 67% efficiency I’d set my previous batches to. Seems like I’d finally cracked the efficiency problem!

With the boil finished, wort cooled and yeast pitched, another gravity reading showed 1.059, when the target was 1.051. Not wanting a 6.5% beer, I used an online calculator to see how much water I’d need to dilute it back. With 22L already in the fermenter, I’d need to add another 3.5 litres to bring the gravity down to 51 points – too much for the 7 gallon SS Chronical.


Once fermentation was complete – FG 1.008, ABV 6.7% – it was time to keg the majority and bottle the rest. I was priming both, so needed to use two different calculations for sugar. For the keg, I worked out I’d need 3 litres of water to dilute the remaining 16L of beer to 5.6%. As mentioned before, the choice of water was critical. Tap water was neither sterile nor deaerated, and I had no time to boil and cool that much. I decided that supermarket own brand sparkling mineral water would do the job at the lowest cost.

I filled the keg with three litres of sparkling water and added the priming sugar, then let the beer flow from the fermenter to top it up to full. With the remaining 1L of mineral water, I added the sugar required for bottling the remaining 6L (using 7L as volume for the calculator). Rather than transfer to a bottling bucket and risk oxidation for such a small amount, I added 70ml of dilution/sugar solution to each 500ml bottle and filled directly from the fv. In total, 26 litres from only 22 in the fermenter.

Final Thoughts

Having gone through this process only once and by accident, there is still a lot to learn from this, however there are also a few points to take away.

Firstly, this seems like a great way of being able to produce enough beer to fill a keg for yourself and lots of bottles to swap with the club members. Secondly, it can help overcome inconsistencies between batches by varying the amount of dilution. Some caveats are also evident though.

I was shooting for a BU:GU of 0.55, but given the higher mash efficiency it ended up around 0.4, which is significant. It shouldn’t bring the beer out of style, but it’s not going to have the bitterness I was aiming for. Dilution is going to make this problem potentially worse. To get around this post-fermentation, an iso-alpha extract can be added.

For recipe creation, I can see two methods that could work. Either create the recipe to the packaging volume, then reduce it to the FV volume without scaling, or reduce the brewhouse efficiency in the recipe profile to account for the dilution as loss. The former seems easier and will take into account the bitterness lost as described above.

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