Originally Posted by a10t2
The rule of thumb is a 10% reduction in utilization. So not a huge difference either way.
I don't think anyone has done any experiment to prove/disprove this. The only way to do it would be to take 1 batch of wort, split it into 2 boils with the exact same hop schedule. 1 batch would use a bag, the other the hops would be free. Then you would need to submit it for IBU testing. Outside of doing something like this, taste testing would be rather subjective even if the difference was 10% which I highly doubt it is. I use a 5 gal nylon paint strainer for my hops like others do and there is plenty of freedom for the hops within the bag even with 3-4 oz in the bag.