FatsSchindee
Well-Known Member
FatsSchindee said:Thanks for the reply, TD. That's a good point about the small addition of 30 minutes more boiling time, relative to the months it'll be before I taste one of these... Might as well! I'll just have to figure out a good boil off rate for 90... Would it make sense to just take my 60 and add half? I'm guessing 1.5 gal pre-boil might leave me with around a gallon after 90 min? I've only ever done 5+ gal, 60 min, batches, so not sure how the lesser volume and more time will affect it. As a test this afternoon, I just boiled 1.5 gal of water for 60 min, and was only left with 53% of that (a 47% boil-off rate!). That's way higher than anything I've ever gotten on the bigger batches (which I haven't measured that assiduously, as I only do partial boils and then top up - so it's not as important exactly how much I lose during the boil. But just from eyeballing it, I know it's never been that much!). The only other reference I personally have is during a 15 min boil of DME and water for a yeast starter - I lost 500ml from a 2.3L boil to end up with 1.8L... That's about 22%, which seems closer to normal. Though again, that was only 15 min. I've heard JZ and JP on Brewstrong say 10-15% is a normal 60 min boil-off rate, and I think I've read something similar elsewhere. I guess that the smaller the volume, the higher the boil-off rate gets? I need to search around here for some more info (I haven't looked through the "one gallon brewers unite" thread yet, because its ridiculously long, but I'm sure there's some good info in there...
Just to update my results, I did end up running both the Oktoberfest and the Bohemian Pilsener at the same time. The boil-off rate for the smaller volume B'Pils was almost what I measured with my test. I decided to start with 2 gal and do a 90 min boil (good advice to try to avoid DMS, since I did a partial mash with Weyermann Pils malt as 33% of the grain bill. And good to hear your we're able to get rid of the DMS in your Helles, TD!). I thought I'd rather be slightly high, and have the OG be slightly lower, than have a slightly lower volume and have to top up (I guess that'd result in a lower OG, too, but preferred to be closer to a "full volume" boil). Anyway, I ended up with slightly more than the gallon I was shooting for. I didn't measure it, but eyeballed it to be about 1/10 of a gallon. I had a theoretical OG of 1.054, and an actual one of 1.050... Running the numbers backward would show that to fit a volume of 1.08 or so, so my guess of an extra 0.1 seems about right (that's assuming my minimash efficiency was spot on (65%), etc). So that is a 46% boil-off, for 90 min. Which is similar to my test in the same pot, but starting with 1.5 gal for only 60 min (47%).... So even an extra .5 gal makes a big difference (33% extra, at those volumes) in reducing the boil-off rate!
And for the O'fest, I boiled 3.5 gal for a hour, had almost exactly a 0.5 gal boil-off, and topped up with 2.5 gal chilled water for 5.5 in the fermentor. At least I have that size rate dialed in! Both are in the ferm chamber at 50* and happily fermenting away...