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Post-Boil or Batch Volume for Hop Bitterness Tool


Apr 2, 2017
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Should you use your Post-Boil volume for the hop bitterness tool instead of the anticipated volume into your fermentor?  How does the hop bitterness tool account for boil-off and losses?
The batch volume is the amount going into the fermenter. The boil volume is pre boil. It uses your inputs and to calculate losses.
I still don't understand how the tool is accurate without any input from an equipment profile to establish losses (boil-off, chiller losses, etc.)
I found this post from a search that appears to support using the post-boil volume

Using the tool alone is not as accurate as the guestimation of IBU within a recipe where the process volumes, gravity, and losses all have an effect on the IBU of the resultant beer.  You must also keep in mind that the calculation of IBU in the final beer is purely a SWAG (Scientific Wild A$$ Guess) as the models really only give results based upon the tested end of boil values for the process the wort was created.  It does not take into account the effect of yeast strain and fermentation vigor on the presence of bittering compounds remaining in the finished beer.

While I am not sure why your need for the tool, I highly recommend bench marking your perception of bitterness between your beer and a commercial beer of similar style with a known IBU.  That said, there are not many craft breweries who do actual IBU tests but are reliant upon sensory panels for consistent product out the door.  So test results from some of the bigger craft names would be the best products to use for comparison.  Sierra Nevada Pale Ale is one of the better beers to use as a standard and there are certainly good clone recipes out there to use for side-by-side tastings.

Thanks for the response.  I was planning on doing a parti-gyle for the first time.  I am brewing a Doppelbock and want to follow it with an Altbier.  The last big beer I made (Scottish Wee Heavy), I felt like a left a lot of potential beer in the mash tun.  My equipment profile is pretty accurate for my process.  I am confident of being able to hit the numbers of the Doppelbock recipe, but want to develop the Altbier recipe on the fly.