There have been a rash of thefts in my school in the last year. My father, a chemist, put me onto the idea of placing an MP3 player, treated with a chemical that would stain hands or otherwise identify the thief, in hopes of the thief taking it and therefore, unwittingly, marking himself. Obviously, this stainer would need to remain on the skin for at least a week, provided no chemical cleaners are applied. However, after a look on Google, it was suprisingly hard to find such a stainer. Does anyone know of one? We have a chemistry lab, so if it's possible to mix this stain together manually, a description would come in handy.