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. 

Dan Sullivan tapping sugar maples on a clear day in early March of 2015. This year brought record snow to Vermont, so sugar season started a little later than normal and lasted longer than expected. 

Dan Sullivan tapping sugar maples on a clear day in early March of 2015. This year brought record snow to Vermont, so sugar season started a little later than normal and lasted longer than expected. 

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.

Each of the 5,000 taps are individually drilled and set. They might not be as picturesque as the brass bucket dangling from a nail, but they're a lot better for tree health. 

Each of the 5,000 taps are individually drilled and set. They might not be as picturesque as the brass bucket dangling from a nail, but they're a lot better for tree health. 

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%. 

One set of taps is so near to the Bunker Farm that sap collected from those trees can be drained directly into the tap house through a gravity-fed line that crosses Bunker Road. 

One set of taps is so near to the Bunker Farm that sap collected from those trees can be drained directly into the tap house through a gravity-fed line that crosses Bunker Road. 

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.