Double Mash for Hi Grav. - any tips?

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pjj2ba

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I generally don't brew big beers, but I just bought a bunch of new grain so I've decided I need to use up last year's buy. I've got Pils and Munich and Vienna to use up. I'm thinking Imperial Alt, (a super sticke) and either an Imperial Kolsch or an over the top Belgian strong.

I was reading in Radical brewing and it mentions a double mash where you basically mash as normal, and then take that wort and use it to mash in a second set of grain. I'm figuring I'd mash as normal and batch sparge with only enough water to compensate for the water to be witheld by the second set of grain (1.5-2 gal). I'll probably mash a little bit thinner and cooler to get a highly fermentable wort, although I might do the second mash warmer. I'm not concerned about efficiency, my goal is to use grains up.

How does this sound? Any tips or advice?
 
I would just do 2 mashes. I think you will have no idea what gravity or efficiency you will get using the method you are talking about.
 
Two mashes would mean a lot of boiling!! One possible issue is solubility of the sugars. I checked the solubility of maltose and it is ridiculously high even at 20 C (57 lbs in 6.5 gallons!!) so that is not an issue. I've looked around for references to see if beta-amylase is subject to feedback inhibition (biochemistry mumbo jumbo) as that might limit conversion in the second mash. So far no luck. If there is no feedback inhibition than efficiency shouldn't be that much lower than normal.

I actually don't care what the efficiency is as I'm looking to use up some older grain. I'd take a gravity reading pre-boil and then make any adjustments as needed to the hop schedule.

According to Randy Mosher's book this is a several hundred year old technique for making high gravity beers. He says that the max pre-boil OG for a typical all grain mash is about 1.060. To get it higher one must either add sugar, add malt extract. Higher final OGs can be achieved by lots of boiling. I'd like to avoid that and this method looks interesting, apparently first runnings of 1.100 are possible.
 
The method you are describing is talked about in a recent BYO article. They refer to it as 'reiterative mashing.' Supposedly works great, and I plan on trying it sometime. Let us know how it works out!
 
I did a no sparge for my barleywine partigyle and the preboil runnings came out to 1.079.

So, if you have the space in your tun to do it, it would be a better use of time to do a no sparge and use the second runnings for a small beer.

28 pounds of malt gave me 5 gallons of 1.118 (120 minute boil) and 5 gallons of 1.052 (60 minute boil).
 
Just thinking out loud here but couldn't one use a march pump to recirculate 5 gallons of water over a grain bed of any size? If I didn't have enough water to cover a grain bed (because it was so ridiculously large) it could just be continuously drained out the bottom and reintroduced at the top. Eventually all the sugars that were there would come out.
 
When I do a double mash I use 2 ea Rubbermaid cooler/mashtuns concurently so my mash takes the same time as a single mash. If I am making a big beer I use only first runnings for 12 gallons and as much of second runnings to hit my OG. The remaining runnings are used for a session ale. Nothing goes to waste and I get good efficiency too. I can make 20 to 25 gallons total.

I use a refractometer to get my gravity right. It saves time and beer.
 
I just read up on this last night, and a double mash is in my future.(I'm thinking of a big beer that I'll brew this year for next holiday season) Anyone know if it's possible to predict an SG with brewing software using this method?
 
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