Euge, if you have a chance, would it be possible to give me an example of how you would go about calculating the total volume of cool water to start with? How much water would you mash with and then how much you would batch sparge with to get your preboil volume? Assuming you mashed 9 lbs of grain and wanted to end up with a batch size of 3.5 gallons.
If you have the time, I would appreciate it...this is the one variable of my brewing that is giving me the most trouble right now.
bbump22, from my website at www.dennybreww.com
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
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 well, then vorlauf and runoff as before. These two runoffs will give us our pre boil volume of 7 gal. of sweet wort.