January, 2016:  

Kids, making maple syrup crystals is a fun project! They are an alternate flavorful sweetener in drinks or other treats because maple syrup crystals have a more complex flavor than sugar crystals or rock candy. Here are two methods for making maple syrup crystals. Note you must use pure maple syrup and not one of the popular commercial brands made with high fructose corn syrup and molasses.

Method 1

Have an adult partner heat a cup of pure maple syrup in a pan over medium heat. They need to stir and heat the syrup until it starts to thicken or crystals are seen forming on the bottom or side of the pan. Your adult partner will then pour the syrup onto a chilled plate and allow the syrup to crystallize. If a dark-colored plate is used then it will be easier to watch the crystals form.

Method 2

Cover a baking sheet or shallow dish with a scant 1/4” layer of water. Freeze the dish to make ice. Have an adult partner heat maple syrup as above, and remove the pan from heat. Remove the dish of ice from the freezer. Then your adult partner can drop spoonfuls of the hot syrup onto the ice. The sudden temperature change will cause crystals to form within minutes.

Maple syrup is a mixture of sugars, water, and minerals. In addition there are small amounts of organic acids, amino acids, proteins, phenol compounds and even a few vitamins. The variation in the latter ingredients gives maple syrup the broad spectrum of flavors from different suppliers (this is similar to honey).

At 66°Bx * the sugar is completely in solution and it is a stable solution. When heated, the concentration of sugar increases as water is lost. The sugar remains in solution at the higher temperature even though much of the water boils away. After heating, there is more sugar than can remain in solution at lower temperatures. The solution is said to be super-saturated. Agitation or stirring can cause the sugar to crystallize and come out of solution until the sugar in solution reaches a stable concentration for its temperature. The fact that sugar solidifies into crystals is extremely important in making confections.

Controlling crystallization is quite tricky and depends on temperature and time. You might try both methods above to see if the crystals appear different to your eyes.

* Bx is the abbreviation for Brix, a measure of the sugar concentration by weight in an aqueous solution. So 66 degrees Brix means that 100 grams of solution would contain 66 grams of sugar.

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References:
http://chemistry.about.com/od/sugarcrystalsrockcandy/a/Maple-Syrup-Crystals.htm
Cornell Maple Bulletin 202 (2007) by Stephen Childs

Editor, Dr. Kathleen Carrado Gregar, Argonne National Laboratory