Volume Question

Hi all. I use Beer Alchemy for Mac. When making a new recipe, it asks for my "volume before boil," and "volume after boil." It is defaulted for 6.08 gallons before boil and 5.25 gallons after boil. However, when I boil, I boil 1.5-2 gallons of water, add the DME, and when the boil is done, I add it to a carboy that has 3 gallons of water in it. The software also has a spot for "water added to dilute." Is that the water you add to top it off?? I didn't pay much attention to these figures, but if I set them to my start of boil (1.5-2) and end of boil amounts, my numbers, such as IBU are significantly affected.

Not familiar with that software but that sounds correct. Set pre boil volume to the amount you used, post boil should be what is left after evap. then dilute water to top up to 5 gal.

Your IBU values are affected because the utilization of the hops is related to the gravity of the boil. So you definitely want to put in your correct values so that you get proper hop amounts in your recipe. If you design your recipe for a 6 gallon pre-boil but only ACTUALLY do a 2 gallon pre-boil you are going to get A LOT less bitterness and flavour from your hops - meaning that to do a concentrated boil (as you are) you need more hops to achieve the same IBU value. The software will account for this for you, that is why it asks for the values.