Originally, hops were used in large amounts so the beers could be exported without spoiling. Hops provide an antiseptic quality that, combined with high alcohol content, allows strong ale to be aged for long periods of time. When planning what hops to use and when to use them, there are a few things to consider. The longer the hops are in contact with the beer, the more impact they have. The way in which they are used is also important.
Hops placed in the boil have heat on their side, so contact time is reduced.
Dry hopping allows the slow absorption of fragile hop aromas and flavors that may be lost in the boil. A cheesecloth bag with inert weights, like marbles, works well to submerge the hops. Lots of hops are needed to balance all that sweet malt. And that s compounded by the fact that as wort gravity increases, the amount of utilization we extract from the hop is decreased. IBU is complex to calculate.