Calculating amounts of hops?

[Erik the Anglophile]

I have been having some trouble hitting my final volume in Beersmith, and come to realise with my process the actual cooling loss/shrinkage is more about 2% rather than the pre set 4%.
This lead me to think about calculating flavor and aroma additions. Lets say a brew an ESB where I want to add 4g/L at a few minutes left for aroma, do I count 4x the post boil vol or 4x the post cooling final vol?

 

[hottpeper13]

Right or wrong , I don't know ,but I always figure IBU's and flavor /aroma amounts on the final volume, cool, end of boil. So my batches in order to get 5 gal into kegs ,are 6 gal and 11 gal

 

[Erik the Anglophile]

yeah that seems the most logical, I also make my batches slightly larger than I plan on getting into my bottling bucket to account for losses while strainng the wort on its way to the fermentor, absorption by yeast cake and that little bit you cant get out without getting a ton of yeast aswell, samples etc.

 

[ChiknNutz]

A while back I went thru the calcs of water expansion as I was having trouble with hitting desired numbers. As it turns out, it is different at different temperatures and is NOT a linear relationship like you'd think. Check this out if interested - Water - Density, Specific Weight and Thermal Expansion Coefficient
However, I take three volume measurements during the brew process (I do BIAB)...when first measuring strike volume, at mash temp and right after boiling. As it turns out, at mash temp it is close to 2% and at boiling close to 4%. As such, I created a simple spreadsheet to assist me in this endeavor, accounting for the size of my kettle. See if accounting for these different expansion rates helps.

 

[CascadesBrewer]

This lead me to think about calculating flavor and aroma additions. Lets say a brew an ESB where I want to add 4g/L at a few minutes left for aroma, do I count 4x the post boil vol or 4x the post cooling final vol?

Using your 2% cooling value, you would be calculating between, say, 20L and 19.6L. This would mean 80 grams of hops vs 78.4 grams. With all the variables in brewing, I would not worry much about 1.6 grams of hops.