[homoeccentricus]

This morning. I measured the boiloff in my 20L BIAB pot. It's around 20%.  However, last time I brewed, the boiloff was way lower. Question: is there a big difference between simple water boiloff and word boiloff, or did I simply not boil hard enough last time?

[dkfick]

I wouldn't measure it so much as a % but as volume.  I find rather I boil 5 gallons of 15 gallons in a pot I get almost the same volume loss over a specific period of time.

[homoeccentricus]

Yes, ok, volume. But the test boil was with the same amount of wort that I boiled last time. Water boiloff was about 3 liters per hour, which seems to be pretty consistent with a 30 cm diameter pot. But my wort boiloff was a lot less. No idea why.

[duboman]

Were the environmental conditions the same, meaning temperature, humidity, etc. More humidity in the ambient air will reduce boil off as well as warmer temperatures.

Also, keeping your actual boil consistent which can be difficult sometimes depending on your burner.

[homoeccentricus]

I boil the wort on my gas stove in the kitchen. Not a big burner. I think subliminally I boil less vigorously to keep the wort odor out of the couch :-(