Re-iterated Mash

[Cloud Surfer]

I recently did a Barley Wine with a 15kg grain bill. I ended up having to use all my water to mash with, leaving nothing over for sparging, so efficiency was down quite a bit. So I'm about to do an Imperial Stout, and thought this time I would try a re-iterated mash. Haven't done this before but it looks pretty straight forward.

So I divide the malt in half, mash in, then sparge to bring the volume back to the original mash in volume and then dough in the second half of the malt, then sparge again up to my pre-boil volume. Is that it? Seems like a simple way to get much better efficiency. I can't see any downsides except the extra one hour it takes for the second mash.

 

[Talnoy]

So I divide the malt in half, mash in, then sparge to bring the volume back to the original mash in volume and then dough in the second half of the malt, then sparge again up to my pre-boil volume.

The few times I have done it I skipped the sparging, as the main goal was as high OG as possible. Put all the specialty malts in the first half (cannot remember why though)

 

[duncbrewer]

That's how I did it for a barley wine in the Robobrew 35, I actually also did a partial parti gyle on the remnants, sort of a second run through of both mashes into another container which I boiled up later. Made about 1034 beer from it.

 

[Cloud Surfer]

The few times I have done it I skipped the sparging, as the main goal was as high OG as possible. Put all the specialty malts in the first half (cannot remember why though)

I was just going to spilt the malts 50/50, but I guess mashing the speciality malts first might be a good idea.

 

[Barry]

I was just going to spilt the malts 50/50, but I guess mashing the speciality malts first might be a good idea.

I have done it a few times, recreating old brewing techniques. Usually the mash is split not always evenly but always with a mixture of base malts and specialty malts in each batch. Hope this helps.

 

[MHB]

Not really a fan, the reduced efficiency annoys me, I prefer Parti-Gyle.

There is a very handy little equation that lets you work out pretty much what you will get both in terms of Volume and Gravity.
You need to work out the yield potential of your grain bill, or you can cheat and just use a stab number. Good quality base malt will have a potential of 77-78% (that’s GCAI Coarse Grind As Is) if you add a fair amount of specialty malt that will reduce your potential a bit I find using 76% gets real close.
oP first runnings = Yield% / L:G+Yield%
Assuming 76% potential (0.76) and you mashed in at 4:1
oP First Runnings = 0.76/(4+0.76) = 0.1597 as a percentage 15.97oP or 1.064
If you shove the equation into excel its easy to use Goal Seek to calculate your target OG, say you wanted 1.090, or 22.5oP, the required L:G comes to around 2.62:1
Say you can fit your 15kg of malt and the 33.9L of water into your mash tun. Given you retain about 0.9L of water/kg of grist you would run off 33.9-(15*.9)=20L of 1.090 wort.
This should have been heated to mash out (~80oC) so its going to be fairly stable, just put it aside until later.
If you have taken 20L of 1.090 (22.5oP) out of the grain from mass of extract = V*SG*oP you have taken 4.9kg of the grain weight out.
Starting with 15kg with a potential of 76% you have 11.4 - 4.9 = 6.5kg left to get.
You can get most of this by sparging, I would add 20L of 80oC treated water, leave it stand for 15-20 minutes and then start sparging, either do a batch sparge (its not too hard to calculate from the equation above how much, how strong you can get)
In the old days they would do First Runnings - Strong Beer, Second Runnings (a batch sparge) - Table Beer, Third Runnings another batch sparge to make Small Beer - safer than drinking the water.
You can combine second and third runnings and get most of the potential extract into a fair sized 1.050 batch. Just make sure your sparge water is well acidified and ideally has the same salt profile (well at least enough Ca).
Mark

 

[Cloud Surfer]

RIS brew day was today and it went really well. I did the re-iterated mash, splitting the grain bill in half. Mashed the first 6kg for 60 minutes then the second 6kg for 90 minutes, followed by a 120 minute boil. Mash efficiency was 64%, which I was happy with as I ended up with 22L of wort at 1.112 OG. So I’ll get my RIS target around 12% ABV.

I wouldn’t have got that OG out of 12kg of malt with a single mash/no sparge, so I think this worked well for what I was trying to achieve.