Producing pure maple syrup is a time honored tradition in Vermont. Whether you are a large producer filling drums and selling on the bulk market or a backyard producer making just enough for family and a few lucky friends, syrup quality is critical. There is too much time and effort involved to risk having the finished product spoil or otherwise become unusable. Perhaps the most critical element of syrup production is boiling until the syrup is the correct density. This process can be challenging if you are inexperienced or dealing with small volumes of syrup. Correct density syrup is between 66.9 and 68.9 percent sugar. Syrup that is low density will likely ferment or grow mold and syrup that is too dense will develop sugar crystals that are difficult to use. It takes a long time to boil sap to syrup. Sometimes the process can feel like it takes forever and that it will never reach syrup. But as you approach syrup density the changes can be rapid. This is the critical time to be paying attention. A good quality thermometer and a maple syrup hydrometer are needed to correctly measure density. For more information about how to correctly measure syrup density, search for University of Vermont Extension Maple.