I'm afraid I can't answer for sure, as I've never used the microwave to dry herbs, but perhaps you need to use a lower power for the basil? I was going to use my oven to dry some basil, as the plant I have is too big to come in for the winter. At least, I have no room for it right now. I will have to play with the microwave and see if I can figure out how to make that work for drying some of it.