Will a hood vent increase rate of evaporation?
I'm boiling down some maple sap this year on the stove top. A bit late but thought I'd give it a whirl even if it only yields a quart or two of maple syrup.


It takes between 20 to 60 quarts of sap to make 1 quart of maple syrup.


  Will keeping the hood vent on increase the rate of evaporation?


You'll want to do it outside, too much steam; sap is mostly water. If you are insistent on doing on the stove top then keep the hood fan on, enjoy the smell, and be prepared for flies and bees to have an inexplicable attraction to all the surfaces near your stove.

Your kitchen stove's hood fan is too far away to affect the boiling, or capture all the sticky steam. 20 quarts is 5 gallons, and 60 is 15. A 6 gallon pot is approximately a foot diameter and a foot high. Providing those measurements in metric won't make it seem any easier. :)


  Conventional logic makes me think yes, but I just read a few threads on this topic and left feeling a bit confused since some people indicate that the hood reduces the surface temp and creates an inconsistent boil which can decrease the rate of evaporation.


Venting is necessary, even outside it's desirable, just to get rid of the steam. In your case you'll want to vent, and there'll be no effect on the temperature. Professionals vent, those that don't say that the next thing they are doing is inquiring about getting some vents.

Check out these two threads, it's all steam; everything will be soaked.