I'm making figurines mostly of gumpaste alone, but a few colors have a little MMF mixed in. They'll have a week and a half to dry. Will they be able to withstand a hot car on a drive to Yosemite?
I assume it would be okay, right?

Once fully dry they should be ok with the heat, it's just the humidity you've gotta watch! Have the air con on cool in the car and I reckon they should be fine

I know for a fact they are not heat resistant...I made a cake for a competition and the flowers came melted..not fun!
Edna

they will hold up. I made a bride and groom as well as some lilies and drove about 200 miles in the middle of summer (and SA summers are hot!!!) nothing happened. The only thing I would suggest is put in in the car, not the boot so that its not in a hot un-aired place.

heat should be ok, moisture not so much.

Humidity and UV rays are the biggest killers of gumpaste. If the pieces are completely dry, then they should be fine. This is assuming that you are transporting them in a air conditioned vehicle. While driving, they should be fine, but if left in the car for extended periods could really cause some problems.

Good luck.

Michele