I really have no idea. This was the first one that I have made. If I had put them on a light string I don't think the lights are strong enough to melt the wax if they happen to touch. I don't think Christmas tree lights would melt the wax either if you were to string them on a tree. One caution I would tell my customers is to store in cool, dry place when not in use. I hope Connie comes along and tells us what she thinks but I'm not sure if she has any wax pieces in hers. Janet