Maple syrup is, in essence, a forestry product. In late winter, sugar maples and red maples are tapped by drilling a small hole in a carefully selected place. Each tree is only tapped with one hole per season, unless it is an exceptionally large and healthy tree. A small, sterile spout is then gently tapped into the tree and connected to a length of tubing hooked into a web-like network that leads to a central collection tank.
The lines are held under a powerful vacuum. This not only allows syrup makers to collect more sap, but also maintains a sterile environment inside the tap lines. When conditions are just right (nights below freezing, days above freezing) sap begins to run out of the tree, through the lines, and into the collection tanks.
But getting the sap out of the tree is just the beginning. Thin and watery, sap is just 1.5% to 3% sugar when it leaves the trunk. After collection, the Bunker Farm runs the sap through a sophisticated reverse osmosis filter, which removes enough water to increase the sugar concentration to between eight and 14%.
Finally, this partially-reduced sap (called concentrate) is cooked in a pan-shaped evaporator. Relying on the principles of thermodynamics, the evaporator moves the somewhat-sweet concentrate through a maze of open-top heating chambers, removing even more water in the form of steam and creating a finished product with that delicious sugar concentration of 66.9%. The Bunker Farm uses a traditional wood-fired evaporator to cook the syrup, which is fed by firewood made from old or damaged maples culled to maintain forest health.