First-Wort Hopping and IBU Calculations

Ok, so if I were to drop an ounce or two of hops into the boil pot while sparging a mini-mash, what would the IBU calculations look like?

Example: Say I was going for an IPA with 75 IBUs; and I was looking at some Chinook or Columbus for the boil, and some Amarillo for flavor and aroma, but I also wanted to tame the bitterness a bit while maintaining the IBUs and that initial bitter punch either of those 2 C's will give you.

Would I put ALL of my bittering hops in the FWH step, or hold some back? 1 oz in the FWH and another oz in the boil at 60 minutes?

Seeing as the hops that get tossed in a FWH step are still going to boil for 60 minutes, wouldn't they produce the same IBUs, or does steeping the hops generate additional IBUs?

The assumption or conventional wisdom (also in the BSmith formula) adds 10% to FWH.  I presume due to the extended steeping and boiling time. 

In my personal experience (sample size of one), I set the FWH to a minus 10%, because I do FWH almost every time, and I found from competition feedback that I was routinely under-hitting the perceived bitterness. 

It's tough to know the actual IBUs, but I do think the FWH technique smooths out the perceived bitterness, so that more actual AA% is needed to hit that desired perception.  YMMV. 

Thanks for pointing out that calculator - probably saw it some time ago but didn't know what it was then so I ignored it. Ok, so when I changed my boil hops to First Wort; it did add about 10% or so to the calculated IBUs in my recipe.

Previously I had just moved the boil hops forward from 60 to 50 minutes in an attempt to reduce the risk of harsh bitterness if the cohumulones were at or above 30%. But if I can leave them at 60 and "mellow" them a bit by steeping them pre-boil... Does this sound right?

Denny Conn had some samples analyzed and the results
Quotes from Denny
" In a split batch I did, one with only FWH Cascades and the other with the same amount of the same hops at 60, the analyses of 2 different labs showed the FWH beer to have on average 10% more IBUs. Blind traingle tasting done both here in Eugen and by Jamil Z. in CA, each with a combo of homebrewers, pro brewers and BJCP judges showed remarkably little ability to tell a difference between the 2 and a slight preference for the FWH beer. Personally, I use FWH often (dozens, maybe hundreds of times) and tell myself that it _tastes_ (and bitters) like a 20 min. addition, so dammit, that's what I'm callin' it!"

"It's subjective, but to me FWH come across as a 20 min. addition. In Promash I set FWH utilization to -65, which equates to 20 min. in a 60 min. boil."

@ MaltLicker: If you adjust the calculator to use -10% instead of the default +10% for FWH, don't you also need to change the original boil-time you had before you moved the hop to FWH since its "perceived flavor" should still be that of a 20-min addition, but the utilization would be consistent with the full boil time? This of course assumes you are starting with an existing recipe having a 20-min hop addition.

Example: If I took some of my hops out of the 20-min slot and placed them instead in the FWH slot, the calculator would add 10% to the IBUs - consistent with what tests have shown. But because those particular hops are now going to be exposed to the full boil time, shouldn't the time in that hop's profile be changed from 20 to 60 minutes to more accurately express the IBUs? This would constitute significantly more calculated IBUs.

Could BS2's calculator be configured to force the "Boil Time" into the hop profile when FWH is selected? (It would be nice if there were a check box in the Options - Bitterness set up for "Calculate FWH based on boil time", no?)

Or is it still just a matter of perception that the FWH method produces a smoother hop bitterness and even some aroma and flavor normally associated only with "flavor" or "aroma" hop additions?

In other words; are you adjusting your calculator from +10% to -10% so your IBUs will show a lower number when FWH'ing to remind you that, according to perception, you may need to add more hops somewhere in the recipe to bring your "perceived" IBUs back up to where you want them?

I guess I should've also asked; do you formulate your recipes to include FWH from the start, or do you build your recipes using the typical hop additions, and then decide which additions to pluck and place in the FW?