In the experiment for the estimation of transition temperture of salt hydrates ,why are we adding a little amount of salt to the salt hydrate solution after when the the temperature has been lowered to 40^oC?

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On the few occasions when the transferred mixture had
not begun to crystallize, the transition was initiated by adding
a small quantity (1 to 5 g) of powdered hydrated crystals.
When it was necessary to take this approach, we found that
using finely powdered crystals generally resulted in a more
rapid recalescence and a flatter plateau than did a few large
crystals.