I find this a tough one to answer when asked by customers or by those attending a honey bee educational talk. I discuss how it proves honey is pure when it crystallizes and how to properly reliquefy it etc. But for the WHY I am not satisfied with my answers in that department. Got any simple explanation ideas I can use?
Honey is a solution of sugars (and other things). Under the right conditions, the glucose comes out of solution, in the process losing its waters of hydration and forming a crystal.
The right conditions include the presence of particulates around which the crystals can form and storage under cool conditions. Honey will crystallize more readily when the glucose content is high, contrasted with high fructose honeys (like tupelo) which are more difficult to crystallize.
As stated above.
Have you ever made old fashion rock candy. Similar ;)
Any super saturated solution of anything will crystallize eventually. Honey is a super saturated solution of sugars. Anything can act as a seed for the crystals to form on, dust, pollen, a bit of wax, another sugar crystal. How quickly it crystallizes affects how large the crystals are. If it crystallizes slowly it will be large crystals and quickly will be small crystals.
http://www.masterbeekeeper.org/dyce/dycelab.htm