[Podo]

hello all.  I have a question about adjusting hop bitterness in a small batch with late extract additions.  In a few days I'm gonna brew a small all-grain 2 3/4 gallon batch of sweet stout, in my effort to experiment with a sweet chocolate stout. 

If I were to mash all the grains at once and boil full volume, I need about 3.6 gallons water pre-boil, and my recipe calculates to 31 IBU, according to Beersmith.  However, I was planning to take a gallon of water and cold steep my dark grains, and add it to the boil with 15 minutes or so left.  So I'd start with 2.6 gallons, and I'm guessing I'll end up fairly close to my final volume when I'm done. 

So I adjusted my batch size in Beersmith to 1 3/4 gal, and it changed my predicted IBUs to 41.  I'm not looking for a strongly hopped beer.  Should I reduce my hop additions to get back to 31 using the smaller boil, or just leave them as-is?  Am I going about the calculations in the wrong way? 

[kylekohlmorgen]

The IBUs went up on your recipe because you reduced the batch size - as far as BeerSmith is concerned, basically making a concentrated version of the original beer.

Since you're going to add that water back in at the end, your final batch size will be around what you initially calculated, and so will the final IBU rate. Make sense?

From a process standpoint:

1. No reason not to add the cold extraction at the beginning of the boil. This will help you hit your evaporation rate. Also, a full-wort boil allows better and more consistent extraction/isomerization of hop acids. Boiling all of the wort will allow you to be consistent with your BeerSmith numbers (since it assumes a full wort boil when calculating the numbers).

2. Cold extraction takes a bit of time, so you might start it the night before, leave it in your fridge, and then add the liquid back at the beginning of the boil.