Batch Sparging question?

[DC]

Hi all, I have recently upgraded my mashtun to a 70L Thermopot and whilst doing my latest brew (McEwans No 1 Champion) I was wondering about batch sparging. I normally do a 2 batch sparge with my old picnic cooler as it only holds 24L’s which was a bit of a pain. So now I have got a bigger mashtun I was wondering if I actually need to do 2 separate sparges? My latest brew was an initial 19L in the mash with grain then a top up of 4.3L then drian off 1st runnings, then 2nd sparge of 15.3L which means I would end up with around 30.6L for the boil.

So I was wondering what if I used the initial 19L for the mash as normal! then instead of heating the 4.3L and topping up the mash and then draining the 1st runnings, I combined the 4.3L top up water with the 15.3L 2nd batch sparge water and just did the 1 larger sparge instead of 2 separate sparges? Not sure if this would affect the efficiency of the brew or cause any other issues

Come on batch sparge Guru’s


Cheers DC

[bigdave]

I believe it will give you a better quality of wort as you're not rinsing out any undesirables from the grain BUT you're also not going to be rinsing all of the desirables (ie, sugars) so your efficiency will drop unless you up the grain bill.

Perhaps do one big sparge and then batch just enough to cover the grains?

[vacant]

Let's suppose after draining your mash tun has 8 litres of wort left in dead space/wet grain (bit high?).

You have 23.3 litres (19+4.3) in the tun before your first drain. If you've stirred and given time to dissolve as much as possible you'll drain 15.3 litres (23.3-8).
15.3/23.3 = 66% of the extracted sugars.

You then add the second batch of 15.3 litres (back to 23.3 litres in total). You have 34% of your extracted sugars remaining, draining again extracts 66% of that, i.e another 22%.

66+22=88%.

However, using one batch of 38.6 litres total (19+4.3+15.3), 30.6 litres drained (38.6-8).

30.6/38.6 = 79%.

You recover 9% more of your extracted sugars using two batches rather than a single sparge/BIAB. Increase your grain bill by at least 9% for a single sparge (500g? 60p).

Other factors? I don't know. As two sparges might take 20 minutes longer then maybe you should increase the mash time for a single sparge to make the extraction time equal?