FWH Treatment

What are the assumptions BeerSmith makes in determining the FWH IBUs?  When I FWH, I transfer wort to the Boil Kettle at the recommended rate of 1 gallon every 5 minutes while the hops are steeping.

Brad touches on FWH techniques and has a bit about how he deals with it in the software in his blog: http://beersmith.com/blog/2008/03/17/the-first-wort-hop-beer-brewing-techniques/

There are so many variants on FWH that a modeling program cannot manage to cover all of them.  This is especially true since there really have not been many utilization studies in conjunction with IBU models to give a reasonable extension onto the current models which are being used.  The other issue that I have run up against is that the bitterness from a FWH addition varies greatly from a boil addition of the same length in terms of perception of bitterness.  While the overall IBU may be the similar (as tested), the perception is greatly different to the imbiber.

Thanks.  I'm conducting a FWH experiment.  BS-3 predicted 25.7 IBU for standard hopping (60 min boil) and 28.3 IBU for FWH.  Lab analysis shows actual 20 IBUs and 26 IBUs, respectively.  I'm not surprised that the FWH IBU is generally higher.  I'm surprised at the spread (6 IBUs) between standard and FWH hopping.  I thought FWH contributed 10% more than standard as rule of thumb (I assume BS-3 uses the same rule of thumb?).  It took 35 mins to steep the FWH before the boil could begin - just wondering if the 35 min steep time could explain the spread.

Looks like you've learned what many of us have known for quite some time. None of the popular utilization models are accurate and IBUs, whether calculated or measured, don't necessarily translate into perceptible bitterness.

Yep - I'll know more about perceived bitterness after I conduct a sensory triangle test with my brew club next month...

Good for you undertaking this work.  I will be interested in hearing your results from the tasting.

Been brewing for about 12 years and learn new things all the time. You can never know too much.