First Wort Hop Addition

[mjo2125]

How does BeerSmith3 estimate the IBU level when a FWH addition is chosen?

[Oginme]

It takes the IBU calculation from the same boil time and adds 10%.  While I don't know that anyone has done modeling around first wort hop additions, it is probably a fair assumption.  Then again, unless you are brewing low bitterness industrial lagers, the whole concept of IBU corresponding to bitterness perception is kind of loose anyway.

[mjo2125]

Any thoughts on the rationale for 10%?  why not 20%?

thanks.

[Oginme]

As I said, I don't know of any modeling around first wort hops.  There are several calculators out there, both connected with software and stand alone and they all seem to use the same figures.  Personally, I only use the calculated IBU as a benchmark to ensure duplicate the same bitterness level from each addition of hops when I change lots (and %AA).  Beyond that, I rely more on my senses when the beer is brewed to tweak the perceived bitterness up or down to match my expectations/desires.   

[BOB357]

Brewed an IPA this weekend on my Robobrew, I took a pre-boil reading (after stirring the wort and adjustment for temperature) with a hydrometer and it was spot on what beersmith said I should have gotten. However after my 60 minute boil the OG was 10 points off, and I got exactly 5.5 gallons into my fermenter with minimal wort left in the kettle. Would think that boiling a wort with a specific pre-boil gravity would result in close to what beersmith would have said. My only though is that maybe the wort in the fermenter wasn't completely mixed as the sample I drew off the bottom was lower and almost the same as pre-boil and the sample i drew off the top was the 1.060 below,

The proper way to pose a question in a forum is by starting a new thread. Posting to an existing thread can lead to misunderstanding for readers. There is no need to pose the same question twice either. It's unlikely that it will get you faster or more responses.

Welcome to the forums and please try to conform to proper forum etiquette in the future. 

[brewfun]

The proper way to pose a question in a forum is by starting a new thread.

True, Bob. Perhaps even an original one. This poster is a copy-pasta spammer who adds links into the post later.

The original is from Reddit a year ago.

https://www.reddit.com/r/Homebrewing/comments/as0cpt/hit_preboil_gravity_number_but/

Welcome to the forums and please try to conform to proper forum etiquette in the future.

Aye! Always sound advice, Bob!

[roundcubeten]

First wort hops are added to the kettle during runoff, immediately after Vorlauf, and allowed to steep in the hot wort as the mash is sparged. Once the full volume of wort has been collected, then the boil proceeds as usual. Those first wort hops, then, might remain in hot wort for as long as two hours.

[Kevin58]

First wort hops are added to the kettle during runoff, immediately after Vorlauf, and allowed to steep in the hot wort as the mash is sparged. Once the full volume of wort has been collected, then the boil proceeds as usual. Those first wort hops, then, might remain in hot wort for as long as two hours.

A good explanation of how its done but not an answer to the original question.