Just saw this post on the BrewBag FB page and thought it was appropriate to share on this thread.
"Understanding that exposing as much of the endosperm to water as possible enables conversion to occur at its maximum. That means crushing the grain as low as your mill will allow. A mill setting of .020 or lower will accomplish this. But you'll make beer above this setting as well.
You need to optimize the grain crush to convert, and use enough water to flush the wort (sugar) from the tun without dilution or change in pH - caused by sparging with plain water - heated or not.
Allow molecular changes to occur without disruption in an optimal environment. pH - temperature - viscosity.
A water to grain ratio of 2.6 or greater was confirmed by Troester as a major contributor to kettle efficiency - not particularly conversion, as conversion will occur to the same degree given enough time no matter the WTGR - but, moving the most converted - non-diluted - wort to the boil kettle occurs when the WTGR is 2.6 quarts per pound or greater.
You'll average 78.5% - depending on the size of the grain bill, large vs small, some will be high 60's some will be high 80's.
Don't toss the baby with the bath water - capture 100% of available wort. If you toss wort with the grain in the tun - you're lowering the total volume of available wort - that lowers kettle efficiency."