It is amazing how much fluid moves up and down the tree trunks. Then we just boil off the liquid in a turkey cooker. We go through a tank of propane to get a quart of syrup, so not the most cost-efficient way of doing it... But it is still fun.
Once it is boiled off most of the way, we take it inside and finish it off on the stove-top. You have to boil the syrup until it boil at 7 deg F above the boiling point of water.