So, in order to prepare for my next batch of beer, I decided to test out my evaporation rate. I filled my kettle with 3 gallons of water, put it on my outdoor burner, and cranked up the heat. Once it started to boil, I turned it down until it was just able to maintain a low boil. I boiled the water for 15 minutes, turned off the heat, then cooled it down in an ice bath for awhile until it was cool enough to handle. I measured 2.69 gallons.
That's a 41% evaporation rate. How the heck could it be that high? I've read all over the forums that it is normally along the lines of 10%-15%. Am I doing something wrong? I did leave the kettle uncovered the whole time, even when it was heating up. Should I leave it covered while it is heating?