When we have enough sap to start the evaporator, we open the valve on the sap tank and let the sap cover the bottom of the pan. It doesn't need to be deep, about 1 1/2 inches is quite sufficient because it boils down faster and makes for better syrup quality. When the sap is boiling, it creates a lot of volume and foam. The deeper the sap, the higher the foam. Then we chuck wood into the fire box under the evaporator pan and start the fire. Before long, the sugarhouse is filled with fragrant steam rising up through the roof vent.
Next we patiently wait, boiling off the sap until it reaches 66% to 67% sugar content (the concentration of sugar in maple syrup). This normally occurs when the sap boils at about 7.25° Fahrenheit above the boiling point of water (about 219°F).
We use a sugar gage to check the sugar content and a candy thermometer and hydrometer to check for the correct boiling point. A hydrometer measures the specific gravity (or the thickness) of a liquid. We use these to assure quality maple products. Some sugarmakers use an age old (but less accurate) technique of dipping a spoon into the sap. At the proper density, the sap will "wax" or "sheet" (create a broad, thin waxy sheet of syrup) on the spoon.
At concentrations under 66% sugar content, the syrup will not store well and can easily go bad. At concentrations greater than 67% the syrup can form sugar crystals. After spending all the time and effort in tapping, laying pipeline and boiling the sap to its critical point, the hydrometer is a valuable investment.
One last filtering and the syrup is ready to be bottled. Syrup must be canned hot (180°F) before it can be stored in a cool place or refrigerated until it's time for serving on your favorite pancakes or ice cream!
