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.
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.
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.
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.
Actually water (or wort) boils at a lower temp at altitude.
One other thing that can affect the evap rate is surface area.
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