There are a variety of sugars in honey including: glucose, fructose, sucrose, and maltose. But the main ones are glucose and fructose, which together can make up nearly 70% of the honey content. Water makes up 18% or less.
The glucose and fructose are the sugars that give honey its “sweetness”. Glucose is the one that influences crystallization. The more glucose in the honey, the sooner your honey will crystallize.
What happens: There is water in all honey (less than 18%). The water binds to the sugars. But water can separate from glucose. When glucose loses water it becomes a crystal.