Now we know: Why does honey crystallise?

It’s all to do with the volume of glucose in the honey, a beekeeper reveals

If you’re a honey nut like myself, you’ll have a couple of jars of the stuff on your shelf at any one time. And, like me, you may have noticed that some honeys crystallise while others do not. While my bottle of supermarket “non-EU” honey (thanks for narrowing down the provenance information for us) has hardened into a cloudy, crystallised spread, a jar of raw heather honey is as runny and golden as ever. When a reader, Sharon Carrabin, wrote in to ask me “why does honey crystallise?” I knew just the man to call.

Noel Leahy is a fourth-generation beekeeper in the Sliabh Aughty mountains in the west of Ireland. He’s passionate about how the treatment of the bees, and the ecosystem in the 150 hives on his farm, translates into superb honey. A fan of the concept of farm to fork, he wants people to know what they’re eating and to understand that the difference between locally produced and mass-produced honey is on a parallel to any other farming product.

So why does honey crystallise? Rather than being a question of quality or purity, it’s actually about the type of honey and its quantity of glucose. “Honey is a saturated solution of two sugars: glucose and fructose,” Leahy tells me. “It’s the glucose that crystallises. So some types of honey are more resistant to crystallisation because they have low glucose.” According to Leahy, dandelion, oilseed rape and ivy honeys crystallise quickly, while clover and blackberry honeys crystallise slowly. “I store jars of honey in my cellar in the same way wine collectors do. Some crystallise in a year and some are runny after six years. They’re both still perfect, it’s just down to the type of honey it is.”

The best way to restore crystallised honey is to pop the jar in a bowl of warm water. Leahy also recommends spreading it on your toast in the morning.


If you want to learn more, Leahy Beekeeping ( run Bee Tours on their farm where you can explore the inner workings of a hive and learn about the process of honey-making.

Have a food question you need answered? Contact Aoife @aoifemcelwain on Twitter or by email at with “Now we know” in the subject line.