The refractometer is the most reliable method to test syrup quality and it is simple to use. The density of liquid sugars is measured in Brix, a unit used commonly in food industry. To use a refractometer, we merely apply a thin layer of syrup to a small glass window in the device. The light passing through the window is bent by the sugar crystals and strikes a printed Brix scale in the refractometer. Clear water on the window gives a reading of 0 Brix.
Maple syrup bends the light dramatically striking much higher on the scale.
This level is set by the float control at the evaporator pan intake pipe. When firing syrup, continually check to see that the float valve is functioning and that there is sufficient water in the holding tank. If water stops coming in, whether due to a system blockage or because of an empty tank, we could burn up the finishing pan. This is a several thousand dollar mistake. Always carry at least an inch of water in the pans and monitor the holding tank volume.