All Grain Brewing :Part 3

Formula and definition of variables

The main concept we're going to be working with is that for the best efficiency, the runoff volumes from your mash and batch sparge should be equal. In order to do that, it's sometimes necessary to infuse your mash with extra water before thefirst runoff. Here's how it works...

R1=initial runoff volume which = mash water volume - water absorbed by grain (assumed to be .1 gal./lb. for this example since that's the way my system works...use your own figure)

S= batch sparge water volume V= total boil volume (amount in needed in kettle for boil) I=volume of infusions for a step mash

R1+I+S(1)+S(2)+S(etc.) must equal V

AND R1+I=.5V

Let's see how this works in a brewing session. Assume a recipe with 10 lb. of grain, and that you need to collect 7 gal. of pre boil wort. A mash ration of 1.25 qt./lb. would require 12.5 qt. or 3.125 gal. of strike water. Based on an absorption of .1 gal./lb., the mash would absorb 1 gal. of water so we'd get 2.125 gal. of water from the mash. Since we want to collect 3.5 gal. (or 50% of the boil volume), after the mash is complete we'd add 1.375 gal. (5.5 qt.) of water to mash tun before the first runoff. Stir the additional water in, let it sit for a few minutes, then vorlauf until clear and start your runoff. After the runoff, we add 3.5 gal. of batch sparge water. Stir it in, rest 10-15 minutes, stir again, then vorlauf and runoff as before. These two runoffs will give us our pre boil volume of 7 gal. of sweet wort.

Now, let's take a look at how to build the equipment and do a brew session!

For the mashtun, you'll need a cooler. I prefer the rectangular ones. The large top opening makes it easier to stir the mash than a round cooler does. Since grain bed depth makes practically no difference in batch sparging, one of the main reasons people use the round coolers is nullified. The rectangular ones are also cheaper. You'll also need a rubber bung for a minikeg, some 1/2 inch ODx3/8 inch ID food grade vinyl tubing long enough to reach from whatever you set your cooler on to the bottom of your kettle PLUS 6 inches, an inline nylon valve, and a length of water supply line with a stainless steel braid for a jacket, and 3 hose clamps. The length of the water supply line doesn't really matter. I use one that's long enough to run the length of the cooler, but my experiments have shown that shorter ones seem to work as well. Feel free to substitute parts if you'd like something a little snazzier. The only really crucial piece of the whole setup is the stainless hose braid, so if you want to put a fancy ball valve or something else on your mashtun, go for it! NOTE: The minikeg bung fits snugly into the hole left from removing the drain in most of the 48-54 qt. coolers I've checked. If the fit is loose, or you're worried about leakage, apply some food grade silicone sealant on the flange before inserting the bung into the cooler. Be creative!

More in the next installment.