Originally Posted by Bobby_M
In addition to flyguy's comment, the reason you'd maybe want to do this on a batch sparge is if you're grain bill is so big that only a single batch sparge infusion is practical, a small "mash out" infusion gets your first and second runnings as close to the same volume as possible. This is a known method of increasing efficiency.
Yes, good point -- I actually missed stating something, but if you are using two batch sparge infusions, then you can achieve the same benefits that I mentioned above by sparging hot. So a mash-out would definitely not be beneficial in that situation.
Regarding the use of a mash-out, I actually disagree with you slightly here Bobby. The only time I split my batch sparge is when I *do* have a large grainbill. The reason is that my tun is full of grain and might not accommodate a large sparge water addition, so I have to split it up. Also, with a large grainbill, your strike-to-sparge water ratio decreases, and those multiple batch sparges really help to keep the extract efficiency up.
When I am doing a small grainbill, I usually don't bother with multiple sparges. I just pull out enough sparge water to balance my runnings, boil that and use it for a mash-out (assuming the temps work out), and sparge once with the remaining water 170F. I found that splitting the sparge infusion took extra time and only increased extract efficiency by a few points, so I often don't bother.