Fri May 08, 2015 3:02 pm
I think its difficult to say a given "time" for fly sparging to be completed. Your main concern should be not over rinsing your grains so as to not pull out any unwanted tannins that may lead to astringency in the final product. Your best bet would be to either use a refractometer or a hydrometer and start taking samples after you have collected 70% of your necessary wort pre-boil volume. Once the refractometer/hydrometer readings start to hit 1.010 or lower you should stop your runoff and top off the remainder of your boil volume in the kettle with whatever treated water you are brewing with.
Completing a fly sparge with this procedure with help to minimize any husky off flavors from the grains leading to the mouth puckering dryness and astringency from polyphenol/tannin extraction.
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