The harvest was small, but mighty. About 4 bars of comb were ready to be harvested. That means that at least 90% of the honeycomb were capped. If I harvest the honey before most of it is capped, then the honey can ferment.
When bees make honey, the forager bees collect nectar from flowers and store it in their honey stomach. At the hive, they give it to the house bees who "chew" it for about half an hour and add enzymes to break the nectar into simple sugars. The house bees then pack the nectar into honeycomb and then fan the nectar to evaporate out most of the water. When the honey has about 18% water, then the bees plug the comb with a cap of wax.