So I finally decided today to actually check my boil off rate. I boiled 160 oz of water for 1 hour and ended up with 102 oz. That is a boil off rate of 36%! Does something seem wrong with this? Seems outrageously high to me.
Insane boil off rate?
- Thread starter sherma
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Yeah, there's a big problem there. You're calculating it the wrong way.
Assuming you covered the bottom of the pot, boil off rates are a constant volume per unit time. They aren't percents of total volume heated. Whether I have 5 gallons or 13 gallons in my keggle, it still boils at 1.5 gallons per hour.
Boiling off 58 oz/hr is a low boiloff rate at .45 gal/hr. Even with a 5 gallon kettle on the stove, I boiled off more than twice that.
Assuming you covered the bottom of the pot, boil off rates are a constant volume per unit time. They aren't percents of total volume heated. Whether I have 5 gallons or 13 gallons in my keggle, it still boils at 1.5 gallons per hour.
Boiling off 58 oz/hr is a low boiloff rate at .45 gal/hr. Even with a 5 gallon kettle on the stove, I boiled off more than twice that.
How "hard" are you boiling? You don't need it to be volcanic. Boiling temp. at sea level is 212˚F. It doesn't matter if the liquid is at 212˚ or 230˚, once it hits 212˚, it's technically boiling. If it's a really vigorous boil, then of course you will have a higher boil off. Once my wort is boiling, I dial it back to the absolute minimum.
Other factors involve ambient air temp. and relative humidity. Warmer air can hold more moisture. In other words, the warmer the ambient temp. is, the more you will boil off. The drier the air, the more moisture it can hold.
If all I've done here is state the obvious it wasn't my intention.
Other factors involve ambient air temp. and relative humidity. Warmer air can hold more moisture. In other words, the warmer the ambient temp. is, the more you will boil off. The drier the air, the more moisture it can hold.
If all I've done here is state the obvious it wasn't my intention.
DirtyOldDuck
Well-Known Member
Boil-off is a constant rate, not a percentage. Assuming you are comparing full, roiling boils, you should boil off the same amount whether you are boiling 3 gallons or 10 gallons. Percentage is not relevant. I can boil off 2 gallons in an hour. If I am boil 2 gallons, that is 100%. If I am boiling 10 gallons, it is 20%. If you boiled off 58 oz in an hour, that is slightly less than a half-gallon - not much.
*I need to learn how to type faster (or maybe drink less while I am typing).
*I need to learn how to type faster (or maybe drink less while I am typing).
Water cannot be heated past 212F (100C) at 1 atmosphere. Cranking up the flame only breaks more bonds, increasing boiloff rate.
Add 1F to the boiling point per 500 ft of elevation about mean sea level.
Ambient air temperature and relative humidity mostly affect evaporation rate, which are minute and we aren't concerned with when calculating the vaporization rate (boiloff rate), because evaporation occurs whether the liquid is sitting at room temperature anyway.
OK, I get that. I guess the fact that I do 1 gallon batches means that I'm just going to boil off a huge amount of my initial volume. Thanks.
SleepyCreekBrews
Well-Known Member
Actually water (or wort) boils at a lower temp at altitude.
One other thing that can affect the evap rate is surface area.
Actually water (or wort) boils at a lower temp at altitude.
One other thing that can affect the evap rate is surface area.
Woops. Too many Hefs. :\
Supposedly water boils at like 160F on Mt Everest.
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