It isnt recommended to make popcorn in paper bags as there is a great
danger of the bag igniting in the nuke.
We got a microwave popcorn maker a long time ago, it was a plastic
bowl with a top that had openings for the steam to come out. It worked
great until someone put oil in it and put a hole in the side.
check around and you can find the microwave poppers and they dont
usually cost too much and they are usable for years.