gmjarvi
Songster
Yep, 40:1 is just about right.The sap is kept at a simmer to low boil so that the water will evaporate. A pressure cooker will keep the water vapor in, so it wouldn't do any good.
The crock-pot on high may do OK, but you still need to be there to stir it so the sugars don't burn. And the crock-pot may not get it hot enough to evaporate the water very quickly and won't hold much sap.
I can't remember the ratio - maybe one of the sappers will chime in - I think it is like 40:1, so that would be 40 cups of sap to make 1 cup of maple syrup ...