Evaporation rate question

[pathfinder22]

Is there any correlation to daytime humidity or night time humidity and evaporation rate?
Even though it is winter time there is still humidity outside, especially when the sun comes out and its above freezing.
Maybe its just a mindset but I seem to boiler harder and get a better evap rate when I am boiling
at night time compared to during the day.
note: I am boiling outside but am sheltered from the wind and rain and such.
Any thoughts on this?

[ecp]

Humidity is a good question. Old timers always boiled at night because they got a better boiler (among other things I'm sure). I always thought this was because of the barometric pressure but humidity could have something to do with it.

[ecolbeck]

I doubt that humidity, time of day, or barometric pressure has any practical effect on evaporation rate. Certain conditions make it appear that more or less steam is coming off the evaporator, but that is appearances only.

[ecp]

Maybe it is appearance (although I'd argue you are wrong). Again, that's just what old timers say. From appearance of my boiling logs, it appears I can make about 65 gallons per hour when boiling between noon and 4:00pm. While it appears, I can make about 74 gallons per hour after 6:00p.m. Just to complicate the matter if you boil under a vacuum (changing the barometric pressure in a chamber) your boiling rate will increase (that's because you are lowing the boiling point of water). If you want to say that barometric pressure doesn't change boiling that's fine, try boiling water at sea level then going to Denver and boil water (you will need higher temps to compensate for the pressure).

[ecolbeck]

Maybe it is appearance (although I'd argue you are wrong). Again, that's just what old timers say. From appearance of my boiling logs, it appears I can make about 65 gallons per hour when boiling between noon and 4:00pm. While it appears, I can make about 74 gallons per hour after 6:00p.m. Just to complicate the matter if you boil under a vacuum (changing the barometric pressure in a chamber) your boiling rate will increase (that's because you are lowing the boiling point of water). If you want to say that barometric pressure doesn't change boiling that's fine, try boiling water at sea level then going to Denver and boil water (you will need higher temps to compensate for the pressure).

Since barometric pressure is unrelated to the time of day, it can't be a factor in your observations.

Water will boil at a LOWER temperature in Denver because the atmospheric pressure is lower. However, what we're talking here about is evaporation rate, which is completely different than the boiling point temperature. Atmospheric pressure may have some effect on the evaporation rate but I doubt its very significant compared to lots of other factors.

[pathfinder22]

Interesting thoughts on both sides of the aisle.
I have only been doing this a couple of years and I know there are other factors involved like wood moisture, suger already in the pan, ect.
This past weekend boiled 30 gallons in 4 hours in the evening with my brother there.
Then, the next day 30 took me almost 7 hours. Maybe having help kept the fire burning hotter.
But it got my to thinking why so much longer for the same amount.
OR
My evaporation rate is all relative to how much beer I am drinking after dark