Hops Alpha Acid %

[festbier]

I'm looking at various recipes that call for higher-than-I've-seen-available AA. For instance, one recipe calls for Spalt 7% AA, but I have only seen 2.6% AA or so. It seems that I have read in the past how to compensate for the lower percentages but I am not sure. Anyone have any recommendations?

 

[festbier]

I think I figured it out (with help from John Palmer). What we want to match is the alpha acid units (AAU), which is calculated by multiplying the AA% by weight in ounces.

So if a recipe calls for .75 oz of 7.0% AA, the calculated AAU will be 5.25. If you have only 2.6% AA available, you would need ~2 ounces to get the same AAU since 2.6x2=5.2

I guess I should have consulted Palmer's "How To Brew" before posting here, but maybe my conversation with myself will be of benefit to someone else.