Correct spelling: pastillage:crazy:
This is a bit confusing. To clarify, pastillage, once made, should be kept well wrapped in double or triple sheaths of Saran and then placed in an airtight container. Personally, I don't like to make pastillage too far in advance of using it. I usually make it the day before. If it's purchased pastillage, same rules apply: well wrapped in an airtight container.
When you are working with it, keep the part you are not immediately working with under plastic wrap and a slightly damp cloth. For instance, I will roll out my pastillage, cut out my shapes, and then keep the rolled out part and cut shapes under plastic wrap with the damp cloth on the plastic wrap.
Once formed the pieces dry very quickly depending on your climate. If you are in a humid climate you might want to dry your pieces in a closed oven. To "dry" the inside of the oven, turn it to the lowest temp setting for about 5 minutes then turn it off and let it cool down. Then place your pieces inside.
The thicker the pieces are, the longer they take to dry. A partially dried piece is much more fragile than a fully dried piece.
Hope that helps........Annie