Granulation is a natural process as honey is an over-saturated solution of sugar.
The two main sugars in honey are
Fructose at 38-40% and Glucose at 35-38%
The glucose crystalises due to its lower solubility.
This means that OSR honey which crystalises very quickly will have a higher glucose content than other honeys that are slow to crystalise.
OSR or dandelion honey may have a glucose content of 40% which will cause it to crystallise quickly within a couple of days.
Fructose more than 42% honey will stay liquid for several years. (Acacia and honeydew)
Most honey is somewhere in between and will crystallise after a few weeks … or years …
Humidity and temperature are important.
the glucose molecules must meet up with “seeding nodules” and stick to them.Too much water hinders this, and so crystallisation is slower.On the other hand, if there is not enough water,the honey will be too viscous for the glucose molecules to move and so a “dry” honey will no longer crystallize.
Temperature has a similar effect: a low temperature favours a higher viscosity (that of a honey at 20° is four times higher than at 32°. A high temperature causes the glucose molecules to vibrate and prevents them from forming crystals.
Above 30°C the crystallisation stops which is why honey stays liquid in the parts of the hive that are occupied by the bees.
14’C is the ideal temperature for crystallisation to take place
10’C or less there will be slow granulation
Honey crystallisation speed chart here