Yup, exactamundo.
My understanding may not be correct. I don’t see anything reliable to point too with a quick Google search.
Yep. And even assuming the IBU values that breweries post are fairly accurate (not a believer that’s always the case), there’s the impossibility of trying to duplicate their IBUs on vastly different equipment with often much lower utilization, not knowing a brewery’s level of whirlpool hopping, differences in thermal mass of whirlpool, etc. That’s where the wheels often come off. It’s a crap shoot but if you have a decent palate you can get in the neighborhood.
I can’t remember my source either but I’ve tracked down what might be the origin, at the link below. Not sure i trust it as there nothing cited to back it up.
The +/- 1 figure I am talking about appears to be from the lab that measured the IBUs. So the lab is saying that the two samples are 2 IBUs apart but could be 4 IBUs apart or zero IBUs apart.
Did anyone else find that hop turd picture disturbing? [emoji56]
;D I’m not a scientist I’m an artist dammit!
Yes, got that, but they used the wrong word for error. Variance is never negative - it’s a measure of spread. So the report doesn’t inspire much confidence.
I’m tracking, but either way indicates the same end
I’ve never heard that before. When I’ve had beers analyzed, they’ve always been almost exactly what was predicted in Promash using the Tinseth formula.
That has not been my experience.
For Double IPAs yes, they over estimate. For whirpooled beers, the formula does not take that into account. For most beers that use boil hops, it works very well.
There are the questions on how yeast strain and pH influence the finished beer. I think it is up to the Brewer to decide, and do some citizen science if need be.
That’s good to hear. I’ve got to admit, I personally have never sent any samples in for IBU testing, so I can only go based on what I’ve read and heard from others. Of course you know 99% of them are sending in IPAs that have been hanging around for 3 months or who knows what. 
I have no idea if yeast selection has an impact on measured IBUs, but it certainly can have a significant impact on the impression of bitterness I get from a beer. I’ve done a split batch, same wort, and had very different bitterness with two different yeasts.
Yes. A bit.
Am I the only one who is taking into consideration the fact that this experiment pointed out that the beersmith IBU measurements were about 40% more than what the lab analysis resulted as???
I would like to see a bittering hop edition only experiment where we brew one beer with about 40% more anticipated IBUs than the control beer which would be based on beersmiths calculations
That is what I’m interested in
I noticed that too. If your suggested experiment is to test if tasters can tell the difference between 1x and 1.4x bitterness, I am sure the answer will be yes. They were able to taste a difference of only 2 IBU in this experiment.
No I’m suggesting trying to brew a beer that the lab actually reports hitting the expected IBU numbers reported by beersmith so that we have a good estimate to base our own beers off of
It would be interesting to see the results. But for me the best way is to learn through experience what my bitterness estimating method tends to produce in the glass as perceived by me. I know thats not going to sit well with detail oriented engineer types, but I just don’t taste a beer and think ‘hmmm, 27 IBUs’. Honesty, 27 calculated IBUs in one grain bill/yeast combo might be perceived differently in another grain bill/yeast combo. And same IBUs but different types of hops may be perceived differently.
I kind of blame too much focus on numbers on how the style guides are set up. We’re numbers people and I think we focus too much on that. Look at APA for example. Does anyone perceive OG? No. It might help design a recipe but in describing a beer, it doesn’t help as much as an ABV number. But even with ABV, so the upper limit is 6.2%. What if its 6.4% but tastes like 5.9%? I would prefer a color description over SRM. And IBU should be described as well rather than a number. We all know that the number means nothing. The vast majority of IBU numbers are “calculated” but dont say by which method. Lots of brewers just use an AA number from a drop down box rather than the package. How many actually calculate their actual current AA but looking up the drop off rate and figuring out the current AA by time and storage temp? Probably almost 0% of us.
Its all good, I just dont think its all that important in reality
I have to agree here. You don’t taste calculated IBUs.
It’s a nice guide for developing your personal taste in a given recipe and nothing more.