Crystallised Honey: Why It Happens & What to Do

Crystallised honey has not gone off. Crystallisation is a natural, physical and reversible process — glucose separating from a supersaturated solution as solid crystals — and a jar that has set can be returned to liquid with nothing more than a bowl of warm water. Spoiled honey is a different thing entirely, with different signs, and this guide covers both: why honey sets, what the speed of setting does and does not tell you, how to re-liquefy a jar without wrecking the numbers on its label, and how to recognise the one failure that genuinely is spoilage.

Crystallisation is the process by which glucose comes out of honey’s supersaturated sugar solution as solid crystals, turning the jar grainy or firm and lightening its colour, with no change to what the honey contains.

Why does honey crystallise?

Because honey is a supersaturated solution: it holds far more sugar — mostly fructose and glucose — than that amount of water could normally keep dissolved. A supersaturated solution is inherently unstable, and of honey’s two main sugars it is glucose, the less soluble one, that restores the balance by crystallising out. Fructose is much more soluble and stays liquid, which is why crystallised honey is a mass of fine glucose crystals held in a fructose-rich syrup rather than a solid block.

Nothing is added and nothing is lost. The sugars are the same before and after; they have rearranged, not reacted. The colour lightens because millions of small crystals scatter light, and the texture runs from a soft grain to a firm set depending on how fast the crystals formed. Analytical work on honey crystallisation bears this out: in a study of 136 honeys, the fructose-to-glucose ratio and the water content — composition, not condition — were what predicted how quickly a honey set.

Why do some honeys set quickly and others stay liquid?

The floral source sets the sugar balance, and the sugar balance sets the speed. Honey science groups honeys by the fructose-to-glucose (F/G) ratio: below about 1.11 they crystallise rapidly, between 1.11 and 1.33 at a moderate pace, and above 1.33 slowly.

Fig. I · The F/G ratio scaleDiagram

← Glucose-heavysets fastFructose-heavy →stays liquid

RapidModerateSlow

1.111.33

RapeseedPlaced by band

Thyme1.18–1.29Measured range

AcaciaPlaced by band

Measured rangePlaced by band — no value on this page

Rapeseed honey is the familiar fast-setter of UK beekeeping: its high glucose content puts it firmly in the rapid group. Acacia sits at the other end. Thyme honey — the honey of the Cretan hillsides, where the wild thyme flowers from May to July — falls on the slow side of the middle: in a 2025 study of Greek monofloral honeys, thyme samples measured an F/G ratio of 1.18 to 1.29 and showed low crystallisation rates even when seeded with crystal starter and held for 27 days at 14 °C, inside the 10–15 °C band where crystallisation runs fastest. A jar of thyme honey that eventually sets is behaving exactly as its sugar chemistry says it should.

What gives the crystals a place to start?

Surfaces. Glucose does not crystallise readily in the middle of a clean liquid; it builds on something — microscopic sugar nuclei and other fine particles suspended in the honey, a process called heterogeneous nucleation. Those particles give crystals their starting points, and heat treatment eliminates them, seed nuclei included, which delays crystallisation — delays, not prevents.

Be precise, though, about what setting speed means: early setting is consistent with honey that kept its particles, and nothing more. It is not proof of rawness — heated honey also crystallises in the end, and a glucose-heavy source sets fast however it was processed. If you want to know how a honey was handled, texture is the wrong instrument; our guide to how to tell if honey is real covers the checks that actually hold up.

What temperature makes honey set fastest?

Crystallisation is fastest at roughly 10–15 °C. A heated room sits above that band, which is one reason a cupboard jar can stay liquid for a long time. A refrigerator takes honey down through the band and holds it cold, so refrigerated honey usually sets sooner — and since honey needs no refrigeration, the fridge achieves nothing except a faster-setting jar. Store honey in a cupboard, lid tight, away from the oven and the window.

How do you make crystallised honey liquid again?

Gently, with water — never with a microwave. Stand the jar in a bowl or pan of warm water no hotter than about 40 °C (comfortably warm to the hand), stir occasionally, and top up with fresh warm water as it cools. A firmly set jar may take an hour or more. The 40 °C ceiling is not fussiness: it is roughly where food regulation draws the processing line — Hungarian rules, for instance, cap the core temperature of honey at 40 °C during processing because above it the composition changes measurably.

What changes is exactly what raw honey is measured on. Heat drives the formation of hydroxymethylfurfural (HMF) and destroys diastase, the enzyme activity used as a freshness marker — and UK law sets honey’s limits at no more than 40 mg/kg HMF and no less than 8 Schade units of diastase. Those are the two figures we will publish for every batch, so we have no interest in telling you to cook them away: see what raw honey means and what we test. A microwave is ruled out for the same reason — it heats unevenly, and its hot spots blow far past 40 °C before the jar feels warm. If the honey sets again in a few months, warm it again; the process is repeatable.

Is creamed or set honey the same thing?

Creamed honey (also sold as set, whipped or spun honey) is crystallisation done on purpose. The producer stirs a proportion of finely crystallised seed honey into liquid honey and holds it cool — around 14 °C in the published protocols — so the whole batch sets quickly as a uniform, fine-grained, spreadable texture instead of the coarse grain slow natural setting can produce. It is a texture choice, not an additive: creamed honey is honey, crystallised under controlled conditions.

How do you tell crystallisation from spoilage?

The one genuine spoilage in honey is fermentation, and it needs water. Honey with a moisture content above 20% — the legal maximum for most honeys under the UK honey regulations — can carry enough available water for osmotolerant yeasts to grow. The signs are unmistakably different from crystallisation:

• Fermented honey smells sour, yeasty or alcoholic, may foam or bubble at the surface, tastes fizzy or sharp, and can push against the lid as gas forms.
• Crystallised honey smells and tastes like honey, shows an even sugar grain through the jar, and produces no gas, no foam and no sourness.

Grain alone is never spoilage; sourness, foam and fizz are. Two factual notes that apply to any honey, in any state: honey is not suitable for infants under 12 months, because it can contain bacteria that can produce toxins in a baby’s intestines, causing infant botulism; and bee products, honey included, are allergens for some people.

Where does THYMELIA stand on crystallisation?

THYMELIA is a UK brand for raw Cretan thyme honey and bee products from the Chania region of western Crete, where the wild thyme flowers from May to July. Thyme honey’s sugar balance puts it on the slower side of the moderate band — and when a jar of ours does crystallise, this page is the answer: warm water, under 40 °C, and it is liquid again. We have no shop yet, and we name no date for one; when there is, each batch will ship with its HMF and diastase figures published. How we source is at sourcing, and what we will test is at testing.