I dunno. Some brewer said 8-10% is the target boil off rate so being a good soldier I aim for the bullseye.
…and being lazy, I found an online calculator.
I measure mine in gal./hour so it stays constant with batch size.
I don’t actually use % based evaporation for calculations. It’s just a reference value that I calculate.
For actual calculations, I use my 60 min. boil-off amount that was measured.
I was hoping that someone would make that distinction.
It’s a landmark.
For calculations I use just my 60 minute boil-off value. Since i don’t have any batches where I boil for longer than 60 minutes, I forego a time modifier.
It’s also a “fat-finger” fail-safe in my spreadsheet. If i suddenly saw 50% boil-off, it would let me know I entered it wrong.
This is what I do. Comparing pre- and post-boil sg’s works best for me. Since I use an immersion chiller, measuring pre- and post-boil volumes would be difficult, at best, for me. My process may not be accurate but it’s a consistent benchmark for me.
What setting is that? 2.4 kW or 2.8 kW?
2000w. I had to correct my previous settings above. I was 400w off.
And that yields too much or too little boil off?
I’m not alone then. I don’t know my actual volumes, because I don’t know the exact correction for expansion of the hot (but exactly how hot?) preboil wort, just the fill level of the kettle that works based on experience; the only volume I actually measure is chilled wort (with the IC removed of course!) Ensuring the correct approximate volume to the fermenter after losses in trub and hops, and being able to calculate brewhouse yield and efficiency, is all that really matters to me.
What I do record of course is pre- and post- boil wort density. And I know when I got that change down from around 12% in my bad old methods to just 4-6%, the improvement in wort and beer quality was spectacular. So that’s my guide.
I’m of the opinion that unless you need the expansion factor to track volumes, it’s really a useless metric.
Cool water in makes way for cool wort in the fermenter and I cool or temperature adjust gravity readings to room temp.
I only use the expansion factors for wort because I measure volume with a SS ruler. It isn’t used for any other calculations except those height based volume ones.
I see your point — it is much easier to measure pre and post boil density (which we do anyway) vs guesstimating volume.
Today’s Exportbier pre boil was 1.052. Post boil it is 1.056. ~7.2% increase in density.
Me too, no matter what it is.
I use the % as a reference. I use gal/hr in actual calculations, but comes out around that %. I laugh at how hard I used to boil.
Between that and your video, I’d say your system is pretty well optimized. (For some reason my boil moves back and forth too, despite the pattern of heat applied. I don’t understand why, nor do I feel the need too. Change in gravity’s good, beer’s good, that’s what I need to know.)
BTU input and the surface area in the kettle are NOT the components that most directly influence evaporation rate. (OK, you do have to bring the wort to a boil)
All the evaporation equations I’ve seen include a factor that relates how much exchange there is between the high humidity zone (wort surface) and the low humidity zone (the atmosphere). You can boil the stuffing out of your wort, but if there is no exchange with the atmosphere, that steam is going to stay put. If the kettle is fully covered and there is no draft, the only evaporation loss is the steam that leaks around the lid. The amount of water leaving as steam is nearly equal to the condensate that reforms under that lid. That quantity is minor compared to what is lost if the lid is off and there is a breeze blowing across the kettle surface. So don’t forget the impact that atmospheric exchange plays in our boils.
I respectfully disagree with the first paragraph.
Regarding the second paragraph: The fact that ambient temperature, dew point and RH (relative humidity) and lid position also affect the boil-off rate, while obvious, are virtually irrelevant to the point I was trying to make. These factors are assumed to be relatively constant and equal within ones brewing environment from one brew to the next.
That leads us back to the first paragraph.
I have read all of the posts regarding boil off rate and keep wondering how much af an effect it has on the overall beer. My method is not so much calculated, but more experiential. I almost always employ a 60 minute boil and I usually make 10 gallon batches, so for a typical 1.050 cooled wort, I use 15 gallons of water. I will use more water to make up for bigger grain bills (water absorbed by grain), but I can’t see if there is any other benefit to the amount of boil off other than to dial in your system.
Without getting into the weeds, there really isn’t any reason to boil the snot out of the wort. I think most would agree with that. People have been becoming aware of things like boil stress on the wort for a little while now. It has long been considered best practice for commercial brewers and it seems to be catching on at the homebrew level as well.
People report good results when decreasing the boil vigor, including better finished malt and hop flavors, etc.