The Dilema of Scale--to brew 12 gallons or 6

In a previous post, I made the assertion that some beers should be brewed in 12 gallon batches and others should be brewed in 6.  That was at a time when I brewed exclusively 6 gallon batches.  I thought of them as "half batches" on my equipment, and brewed half batches by choice.  Who needs more than two cases of beer from a batch?  Not me, I thought.  But the 12 gallon batch thing was prompted by the discovery that the less headspace I left in the mash tun, the better the mash held temp.  Since that realization, brewing 12 gallon batches has helped a lot with my sub-1045 beers--Blonde Ale, Cream Ale, 70/-, and Patersbier--holding them to the degree for the entire 90 minutes.

I should probably be honest with myself and accept the fact that brewing 6 gallon batches of most of my brews is plenty.  However, after bottling two 12 gallon batches recently (about 4 cs each of Cream Ale and Patersbier), on Thursday I bottled a six gallon batch of Simcoemech (a Simcoelicious APA modeled after Russian River's Row 2 Hill 56).  It smelled so freaking good.  I found myself standing over two full cases of this obviously amazing beer and regretting not having more.  Not a single bottle had been consumed--won't even be ready for at least two weeks--and already I was lamenting the fact that they will be gone far too quickly.

It got me thinking.  Could I brew a 12 gallon batch of Simcoemech?  Problem is, this is a 1.048 OG beer, and I have always considered 1.045 to be the upper limit for 12 gallon batches.  This is because, a 1.045 beer requires about 17.5 lbs of grain for 12 gallons, and that amount of grain plus 22 quarts of water (1.25 qts/lb) fills the cooler all the way to the top.  So how can I fit this 18.5 pound grain bill in my 10 gallon cooler?  I really really want to.  But at 1.25 qts per gallon, the infusion of water with the grain would overflow the mash tun.

Why does the water:grain ratio need to be 1.25?  This is what all my recipes are formulated to.  But it's not an absolute.  The only absolute is that my cooler holds 10 gallons and no more.  What if I play with this ratio a little?  General guidance is that it should be between 1.10 and 1.25 quarts per pound.  So with this in mind, and with Beersmith's "mash volume needed" calculation, I did a little exploring and came up with some theoretical limits.

Turns out, at a water to grain ratio of 1.10 qts/lb, I can brew 12 gallons of up to a 1.051 OG beer.  This assumes 87% efficiency, which is usually what I get on my 12 gallon batches.  That's 19.5 pounds of grain and 21.5 quarts of water, which according to Beersmith will produce a mash volume of 9.95 gallons and fill the cooler.  Pretty tight, but it can be done.

 This includes a mash out at 168, also not an absolute.  If we drop the mashout infusion, looks like we can go up to a 24 pound grain bill at 1.1 qts/lb before overflowing.  That's a 12 gallon batch at up to 1.063 without a mash out!  Wow!

I don't think I'll test any of these limits in reality, but the good news here is that I should be able to brew a 12 gallon batch of Simcoemech with relative ease, just by adjusting my water to grain ratio.

Here are some stats on the brew:

Batch size:  12 gallons
Original Gravity:  1.048
Total grain:  18.5 pounds
Total water in mash:  34 quarts
Ratio:  1.1 qts/lb mash in; 1.84 qts/lb mash out
Mash volume:  9.95 gallons

Of course this is all hypothetical until I actually brew it.  Wish me luck!