Can you reconstitute honey that has crystalized?
Yes, but you must do it carefully.
Loosen the jar lid but don't remove it, and heat the honey by
placing the jar in a bowl of water no hotter than 45 degrees C. A
good rule of thumb is to have the water no hotter than you can bear
to keep your hand in. It may take a while, but eventually the
crystals will dissolve.
Don't be tempted to try to accelerate the process by increasing
the temperature. Above about 45 degrees enzymes in the honey will
start to break down some of the sugars into other substances which
will give the honey a bad flavour. Some people suggest using a
microwave oven, but by doing it that way it is far too easy to
overheat the honey.