BK split

[steve123]

I’m looking to brew 2 La Chouffe clone’s. I have a 70L boil kettle and an old 35 litre boil kettle that just needs an element adding (which I have a spare one). I’m going to do one mash (60 L mash tun), and split the wort into 2 kettles.

I aim to get 38L out of the larger BK and 19 L out of the smaller to go into the fermenter.

I want to do the larger with about a OG of 1.073 and the smaller as 1.05.

I’m aiming for an efficiency of 85%, using brewers friend if I aimed for OG of 1.073 at 38L I would use 10 KG grain and 1/2 Kg sugar, for OG of 1.05 at 19L is says use 3.4 KG grain and 0.18 KG sugar.

So adding these figures together I would use 13.4 kg grain with 0.68 KG grain, using a mash thickness of 2.5 L water per KG grain, this would be 33.5 L water with a water absorption rate of about 13 1/2 kg, giving 20 L wort from mash plus sparge .

My question being how do I split the quantities, from the 20L mash how much do I add to each BK then how do I split the sparge?

 

[Zephyr259]

Wow that's complicated... What makes it even worse is I'm assuming you'll be adding some sugar to these batches since they are belgian? You're doing a partigyle brew, but it has some set rules, if you split the runnings 1:2 then then each portion gets half the extract so you get say 10L at 1.080 and 20L at 1.040. If you split 1:1 then the extract goes 60:40 from memory. The ratio is for the runnings and is kinda meant to work with fly sparging but should mostly work with batch so long as you don't want more in the strong beer than you have in the mash.

You can then blend these sweet worts to give closer gravities which might work well with your desired gravities, some folks also think it vastly improves the smaller beer.

Here's a link to an article that goes into some depth, I've not done this myself yet as the practicalities of 2 boils is too awkward just now but do have some plans in place. I'm going to try an easier approach of splitting my wort pre-boil, taking 10L of wort and boiling it separately should let me get it to a much higher OG in a decent time frame since i can reduced that to 5 - 7 L in 60 - 90 mins.

Good luck.

 

[steve123]

Many thanks for this, this is what I’m after but is a lot more complicated than i first thought, will take some reading and digesting

 

[IainM]

What you are trying to do is a lot easier if you think in terms of total gravity, as described in chapter 5 of Designing Great Beers by Ray Daniels. So, 38L at 1.073 is a total gravity of 38x73 = 2774, and 19L at 1.05 is 19x50=950 total gravity. Add them together and you get 3724, of which, 75% of should end up in the large kettle and 25% in the small kettle. The easiest thing to do is mash and sparge the whole lot to end up with your target pre-boil gravity for the 38L, then liquor back whatever is left to make the 19L.

 

[Zephyr259]

I like your plan Iain, 38L and 19L are the batch sizes thoough aren't they? So we'd need to convert over to using the pre-boil volumes. Running the numbers it is like a 51L batch at 1.073, 38L in the big batch and 13L in the smaller batch which when diluted to 19L should be at 1.050. Slight complication is that if both got an hour boil and lost 3L in that hour then the smaller batch will end up comparatively stronger since it's losing 15% of it's volume and the big batch loses 7.5%. I've been messing with this kinda maths the last couple of weeks as a way to make small batches of really strong beer from the same mash as a regular beer. Brew assuming 23L batch size means 28L pre-boil for me, splitting that 8L and 20L gives me a 5L batch and a 15L batch with out the hassle of splitting the running in a traditional partigyle.