Originally Posted by Evan_L
Isn't points per pound the same as percentage of maximum yield when you get down to it? It doesn't matter what form you put the number in, it's still the same thing. Both are max limited by the same value.
Learning to use points per pound (points per kilogram for those who use the metric system) allows one to quickly and easily scale a recipe up and down in size as well as adjust any given recipe for actual brew house efficiency. If a recipe was based on an extraction rate of 27 points per pound and I know that my average extraction rate is 30 points per pound, then adjusting the recipe for actual brew house efficiency is as simple as calculating a scaling factor and applying it to the grain bill (something that can be performed with pencil and paper).
recipe_extraction_rate = 27 points per pound
my_average_extraction_rate = 30 points per pound
grist_scaling_factor = recipe_extraction_rate / my_average_extraction_rate
grist_scaling_factor = 27 / 30 = 0.9 (10% reduction in the grist mass)
Furthermore, one can adjust any given recipe for one's brew house using only the recipe's O.G., wort volume, grist composition, and one's average brew house extraction rate in points per pound.
ACME Pale Ale has an O.G. of 1.052 and a grist that is 90% 2-Row malted barley, 5% 60L crystal malt, and 5% carapils malt. We want to brew a batch of this beer and keg 5 full gallons from the secondary. In order to achieve that result, we need to formulate a recipe that yields a primary volume of 5.5 gallons while leaving 0.25 gallons with the break and hops in the kettle; therefore, our target volume will be 5.75 gallons. Our average brew house extraction rate is 27 points per pound.
original_gravity = 1.052
wort_volume = 5.75 gallons
extraction_rate_in_points_per_pound = 27 points per pound
grist_weight_in_pounds = (original_gravity - 1.0) x 1,000 x wort_volume / extraction_rate_in_points_per_pound
grist_weight_in_pounds = (1.052 - 1.0) x 1,000 x 5.75 / 27 ~= 11.1lbs
2-Row malt = 0.9 x 11.1 ~= 10lbs
60L crystal malt = 0.05 x 11.1 ~= 0.56lbs
carapils malt = 0.05 x 11.1 ~= 0.56lbs
I did not need a whirling deterministic finite automaton (a.k.a. a computer) to formulate this grain bill for my brew house. All I needed was a pencil and a piece of paper.
And as they say, "not for nothin" but batch sparging is not a dead end street. It's a wholly acceptable way to achieve the same results (even superior results one might argue as there is less danger of tannin extraction from over sparging) the only difference is the few bucks more per batch spent on grains, no pun intended. I'd much rather spend the few bucks than mess with fly sparging, why add another variable and 45 minutes to an already long brew day.
Batch sparging is a dead-end street. It's not used in commercial brew houses for a reason. Continuous sparging produces more extract per pound of grain. Properly performed, wort produced from continuous sparging is also much cleaner than wort that is produced from batch sparging, which isn't sparging at all--it's multiple mashing/lautering. Wort from a properly performed continuous sparge will have less particulate matter and far less tannins than the runoff from a multiple-lautered mash because the grain bed is left undisturbed during mashing and lautering. Contrary to what most forum members believe, performing a continuous sparge properly isn't rocket science.