Are kneaded erasers self cleaning?

Are kneaded erasers self cleaning? To clean a kneaded eraser, you can stretch and knead it until the color turns light grey. Eventually they will become too dirty to use as graphite, charcoal, dust or other particles accumulate in the eraser. So, at some point, you won’t be able to keep using it and then it will be time to seek a replacement.

How do kneaded erasers clean themselves?