Is it possible to bitter a beer after primary fermentation? I was thinking of boiling some more hops in a few cups of water, filtering the hops, and pouring in that infused water.
I dont see why that wouldnt work. I dont know what kind of IBU's you would get out of that or even if you could get that info from brewing software.
You may want to try boiling a small amount and adding it and then taste testing. Keep doing that until you get the amount of bitterness you want.
It works, although there is a limit to how much you boost the bitterness without seriously diluting your beer. A quart of hop tea can increase the IBUs of a 5 gallon batch by 4-5 units.
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