yes, why the heat again?

you want to heat it until it starts to get a bit milky or some solids start to form, this tells you it's saturated. then ideally it stays warm and this gives lots of time for the crystals to form slowly and the impurities don't get into the core of the crystal, the longer you can make it stay warm the better

also, they do the same thing when baking photovoltaic cells... the bigger those crystals are the more efficient they are