evaporation

[therebelmc]

Hi , i would be interested to know what sort of evaporation quantities various people are suffering during boil up process. looking at the calculators for sparging it would seem that 15% is a normal figure. i have today carried out a test on my boiler and lost 9 litres from a start of 25 litres which if my maths still stand up is 36%. seems a lot . Cheers Mick

[boingy]

I lose about 5% per hour but my boil is probably less vigorous than many because I use gas and I can turn it down to a rolling boil rather than a manic boil! I used to lose about 10 to 15% per hour when I used an electric boiler. 36% does seem excessive. How long did you boil for and what sort of power did you use?

[therebelmc]

I too am using gas and boil for 90 minutes. is it possible to use a lid or would that cause problems?.

[Twistedfinger]

Boil vigor and surface area are the main factors, plus relative humidity. Using a lid is a no go as you will keep in the nasties you want to boil off.

Whats the size of your pot. A wide squat pot will have a higher evaporation rate than a tall skinny one of the same volume. One trick is to float a food safe bowl on the wort surface. This effectively reduces surface area reducing evaporation, it also greats a better rolling boil so you can reduce the heat and save fuel.

[deLaCuerva]

i lose about 7 litres, it's independent from the quantity of boiling wort