Boil off

[TimG]

Made one 19L batch in my keggle so far but found the full boil really lost A LOT of volume to boil off. Expected about 5% per hour but ended up with more like 20%??

Did I just have way too vigorous a boil (I thought that was good).. or do we have the right climate to have a higher rate of evaporation (don't see how that could work.. but I definitely lost a lot of volume so something must be up)?

Curious to hear other's thoughts.

[akr71]

I aim for a slow rolling boil - less chance of boil-over and less wort scortching. Whether that is right or wrong, I don't know, but that's what I do.

Of course fermcap helps prevent boilover too.

[mr x]

Humidity and wind will affect the boil-off. I've gotten so used to how my system works that I'm not sure what my boil-off is. There is a guideline in Beersmith...

[LiverDance]

5% in a keggle is too low, especially if you are on propane. The temp outside will have an effect but I never really get into accounting for that. My boil off rate for a 20L batch is 14%. Did you account for loss of liquid in the grain (1l/kg) and any water left in both the mash tun and bottom of the kettle? That could be part of the losses as well.

[mr x]

Yeah, I'm looking at Beersmith, and the default is 9%, but I bumped mine up into the low teens as well.

[akr71]

I checked some of my notes at lunch - I prob end up with 10-15 % evap rate with a 60 min boil.

[hogie]

I'm more in the 15-20% range.

[TimG]

Thanks guys.. I'll keep good track of it and see where I end up. Not sure why I had the 'default' at 5%.. I'll throw in 15% to be safe, I can always add a bit of water if I'm short (but tough to have to boil more to reduce the volume).

Tim

[GAM]

Just curious, what were you making?

Sandy

[NASH]

15 - 20% isn't abnormal for a homebrewing system. The optimum rate is 7% or so, and it would be good if you could all get to that, more isn't better, in fact it's worse, less is worse too. In microbreweries it's usually a challenge to get 5%/hr, most systems get more like 2 - 3%/hr so it's tough to get a 7% evap over a 90 minute boil. Evaporation rate can be controlled somewhat with a half-cocked lid on the kettle but that makes for more boilovers unless you watch it closely and have really good control of your heat source.

Either way you'll still make great beer unless you get down into the 3 - 4% or below evaporation rate over your total boil time. If you boil off too much just add water back to it at the end of the boil to bring it back to your desired volume and gravity.

[chalmers]

If you've got your system dialed in, able to measure the rate, and are consistent, why is more than ~7% bad?

[NASH]

If you've got your system dialed in, able to measure the rate, and are consistent, why is more than ~7% bad?

If you boil off more than the optimum you're going to have more maillard reaction, more colour pick-up, more caramelization etc than calculated for, the overall composition of the wort is changed on the micro level because of this and therefore has an effect on the finished product, it's not that it's bad, but it's not quite the way it should be Not that big of a deal at all if you always brew the same way but it's not the greatest if you try to clone beers since the original made by professionals should have utilized an optimum evaporation rate. It's worse though if you evap way too much and end up with concentrated wort, then your hop utilization can be way off and caramelization can be through the roof. Like I said, you'll still make great beer even with a 20% evaporation rate but you'd make beer more similar to the pros not to mention the energy savings if you get it in the 10% range.

[chalmers]

Good to know! Damn that Maillard and his reactions! Well, too much of them.

[derek]

If you boil off more than the optimum you're going to have more maillard reaction

Well, I had my usual round of screwups brewing this weekend, resulting in boiling off more than the optimum. So I guess I'll be having a mallard reaction. I hope it doesn't taste too much like duck...