I have the Prisma pencils and love them. About a year ago around this time I went to Staples looking for an electric sharpener and ran into a teacher friend. He told me NEVER to use good colored pencils in an electric sharpner as the lead is too soft and the vibration of the sharpener will cause the lead to break before it comes to a point. He recommended a hand sharpener. I still find that the lead will break just as I'm getting the pencil to a point but I've found that unless I'm doing a fine line a duller point works better.