There are four grades of pure maple syrup; Golden Color/Delicate Taste, Amber Color/Rich Taste, Dark Color/Robust Taste and Very Dark Color/Strong Taste. Each grade has a range in color as defined by its light transmittance. Knowing the color of pure maple syrup and into which grade it falls is one of the key elements of grading. Vermont maple regulations stipulate that Golden Color/Delicate Taste syrup has a light transmittance of not less than 75%, Amber between 74.9 and 50%, Dark between 49.9 and 25% and Very Dark, less than 25% light transmittance. Using a temporary color comparator for grading can be effective as long as the amber-colored glycerin samples haven't faded with time or exposure to light. Permanent glass comparators are available and will remain accurate over time but are more expensive. Syrup will naturally darken over time. If the syrup color is very close to the lower limit for a given grade when packed, it will likely be out of grade within a month or two. Sugar makers are advised to keep this in mind when selling syrup in the retail market.