Timing matters. In hopping, it matters because we’re doing a delicate dance that extracts distinctly different things from the hops, and getting more of one usually results in getting less of the other. I’m speaking here about the productive tension that exists between hops oils and hops resins/acids. You have a hop cone. Inside of it are oils, which we generally think of as being the flavor-producing agent.
You also have alpha and beta acids which, when isomerized or oxidized, add bitterness. The trouble is that isomerizing alpha acids is accomplished by boiling them, and boiling drives off the chemicals that make our hops oils so flavorful. This means that we have a construction challenge when it comes to producing beers with both bitterness and flavor—or one and not the other—and knowing what you’ll get out of hops based on when they’re added to the beer is essential to producing the beer you want.
In short, the longer your hops are exposed to heat—and the higher the temperature—the more likely it is that you’re getting bitterness and not flavor, and it may be happening faster than you think. Of the potential bittering you could get out of the hops you add, a majority is produced in just about 20 minutes. At the same time, most hops oils deplete by half or more with just 15 minutes of boiling. Linalool, a lavender aroma–producing hops oil, reaches 50 percent depletion in just 6 minutes.