Wood-fired maple syrup was boiled down over a wood fire, instead of a burner that runs on oil, gas or something else. It describes the heat source under the evaporator. It isn't a grade, and it doesn't mean the syrup tastes smoky.
First, the evaporator
Sap is mostly water. It comes out of the tree at about 2 percent sugar, so it takes about 40 gallons of sap to make 1 gallon of syrup. Boiling drives off that water, and the equipment that does it is called an evaporator.
In most sugarhouses, an evaporator is a set of stainless steel pans sitting on top of a firebox. In a continuous-flow evaporator, which almost all commercial sugarhouses use, sap flows in at one end and moves through divided pans as it thickens. Syrup is drawn off at the other end. Some pans have flues, folds in the bottom that give the fire more surface to heat.
Syrup is generally finished at about 7°F above the boiling point of water. At sea level, that's around 219°F. Then it's filtered and graded for color and flavor.
Then, the arch
The arch is the firebox under the pans. It holds the fire and sends the smoke out, away from the sap. An arch can be as simple as stacked blocks or bricks with a smokestack, or an insulated firebox with forced air.
In a wood-fired arch, flames and hot gases are drawn under the pans and out the stack. Cornell's maple program warns that if smoke or exhaust from any heat source swirls over the pans, syrup can pick up a smoky flavor. The aim, whatever the fuel, is to keep smoke out of the syrup. So wood-fired syrup isn't meant to taste smoky.
Wood versus oil
The two most popular evaporator fuels are wood and fuel oil. Natural gas, propane, electricity and wood products like chips and pellets are options, too.
Wood. Ohio State Extension calls wood the most popular evaporator fuel, partly because it's readily available. It's also hands-on. A wood fire has to be fed at regular intervals, about every 5 minutes, and dry, seasoned wood burns much more efficiently than wet, green wood. That's a lot of trips to the woodpile, and that time and fuel are part of why real maple syrup costs more. A standard evaporator makes about 22 gallons of syrup from a cord of dry wood, and modern wood arches with forced air and insulated doors can be as efficient as oil-fired ones.
Oil. An oil burner makes a ball of radiant heat that hangs under the pans. Ohio State says fuel oil burns clean and hot, suits larger operations, and can make a gallon of syrup on under 4 gallons of fuel. Natural gas works much the same way, where it's available.
So which is better? The Vermont Maple Sugar Makers' Association says every option comes with benefits and challenges. It doesn't rank any one as making better syrup, and it says it has no research showing that one does. Each sugar maker picks what works for their operation.
Where reverse osmosis fits
Many sugarhouses run sap through a reverse osmosis machine, or RO, before it reaches the evaporator. RO uses pressure and a membrane to pull some of the water out, so the sap that goes into the pans is already sweeter.
Less water means less boiling and less fuel. In one example from Cornell's maple program, a small RO raised sap from about 2 percent sugar to 4 or 5 percent and cut boiling time from about 8 hours to 4. Ohio State Extension tells producers that, whatever fuel they burn, RO is the single investment most worth making.
RO and the fire are separate choices. A wood-fired sugarhouse can use RO, and so can an oil-fired one. Wood-fired on a label tells you about the fire, not about the steps before it.
Where wood-fired fits on a label
Wood-fired isn't a grade or a legal category, so it sits apart from the name and grade you check when you read a maple syrup label. The USDA's grade standards and Vermont's maple regulations don't mention fuel at all.
The grade and color class describe the syrup's color and taste, from Golden with a delicate taste to Very Dark with a strong one. Our guide to maple syrup grades explains each one.
How Sticky does it
We boil our sap down over a wood-burning fire, letting the flavor develop naturally. That's what the Wood Fired badge on our tin means. One side of the tin calls it "slow-boiled over real wood," and the other says "wood fired for rich, bold flavor." That's how we describe ours. Taste it and see if you agree.
Our syrup also comes from one Vermont forest and has one ingredient: pure maple syrup. Amber is warm and smooth with caramel notes, and Dark is deep and robust, built for cooking and baking.
