I want to use an invisible zipper for a pocket closing but couldn't find zippers that are ~5" long. So I bought a longer zipper and plan to shorten it. However, I don't like using thread to sew a new zipper stop, threads break too easily and then the zipper slide goes off track. I have used a staple before and that's effective but that can poke into your hand for this pocket. So I looked at the zipper end and saw that it is either glued or melted together.
Back in college, I remembered using a candle flame to melt the raw edges of my nylon backpack to make sure they won't ravel so I thought I would try this. In the picture below I practiced at a spot longer than I needed and then at the length I wanted. I put the coil near the candle flame and watched it melt, be careful once it starts it goes quick. I cut off the excess and now have a short zipper with a permanent stop. This zipper is all nylon.