Double Batch Calcs

[Spencer]

Hi

I am a bit capacity constrained but I want to do double batches (say 50L in total). I am thinking of producing 30L of wort (which is within the capacity of my system) and then splitting it into 15L halves, then adding 10L of water to each batch (in the fermentor) to make two batches of 25L each.

My question relates to recipe formulation......I don't think I have a problem with calculating how much grain I need. I figure I should base my calculations on a 50L batch of a certain OG and ignore the concentration/dilution issue.

But what about hop isomerisation? I don't think I can base my hop calculations on 50L of say 1.045 wort because the reality is that it'll be more like 30L of 1.060??(dunno) wort in the kettle...and I won't get the same level of hop utilisation in a more concentrated wort.

Can anyone help??
Thanks
Spencer

 

[The Mick]

Hi

I am a bit capacity constrained but I want to do double batches (say 50L in total). I am thinking of producing 30L of wort (which is within the capacity of my system) and then splitting it into 15L halves, then adding 10L of water to each batch (in the fermentor) to make two batches of 25L each.

My question relates to recipe formulation......I don't think I have a problem with calculating how much grain I need. I figure I should base my calculations on a 50L batch of a certain OG and ignore the concentration/dilution issue.

But what about hop isomerisation? I don't think I can base my hop calculations on 50L of say 1.045 wort because the reality is that it'll be more like 30L of 1.060??(dunno) wort in the kettle...and I won't get the same level of hop utilisation in a more concentrated wort.

Can anyone help??
Thanks
Spencer

Hi Spencer,I have used this technique for the last 3 batches and had no problems,same grain and hop bill,I end up with 30litres of wort and dilute to 2x20 litre batches which fit neatly ino 19litre kegs
regards
Mick

 

[JasonY]

Lots of ways you can crunch the numbers but you will lose hop utilisation with a higher gravity boil so base the IBU calcs on the actual boil gravity.

 

[Cortez The Killer]

Promash will do the calc for you

You specify your boil volume and total volume

Also from memory there is a particular ibu calculation formula which is better suited for batches where the boil volume is smaller than the batch volume

Cheers

 

[Hutch]

This is certainly feasible, and as others have said, you'll need to up the hopping rates to account for decreased utilisation with the higher gravity boil (Promash or BeerSmith will help with the calculations).

Also, If you're planning on only ending up with 30 Ltrs post-boil (so ~40Ltrs pre-boil), your efficiency might be slightly lower than you expect, so you might want to up your grain bill slightly to account for this. Worst case is that you end up with a higher gravity than you expect, which given that you'll be diluting into the fermenter anyway is not a problem.

 

[sah]

I've done 13 brews like this. Beersmith does my calculations.

I use 15L cubes (they're actually 16 + bit L)

My final volume is 46L = 2 x 16L concentrated wort + 2 x 7L water.

I get 80% efficiency.

This is not detrimental to the finished beer from what can tell.

My mash tun is 45L. Boil volume is about 41L.

regards,
Scott

 

[Stuster]

What post-boil gravity wort are you going for, Scotty? 80% is a good efficiency for a high gravity wort.

 

[sah]

What post-boil gravity wort are you going for, Scotty? 80% is a good efficiency for a high gravity wort.

It varies, some figures from recent brews:

Ordinary bitter. pre boil 1.050, post boil 1.055, post dilution 22L @ 1.040
Hefe weizen. pre boil 1.061, post boil 1.064, post dilution estimated (no measurment) 1.045
Dark ale. pre boil 1.060, post boil 1.066, post dilution estimate (no measurement taken) 1.045
Weizen. pre boil 1.057, post boil 1.061, post dilution 22L @ 1.041
APA. pre boil 1.059, post boil 1.061, post dilution 21L @ 1.042

Accuracy of these measurements will also vary. I'm still learning

regards,
Scott