Ah, Magnesium Ribbon, takes me back to my highschool chemistry classes.
We were told by the teacher, "now everyone come up and get a 1" long bit for your experiment". 2 Minutes later the jar (which probably had about 10m in it to begin with) was completely empty and the last kid up to the front missed out.
All the rest of us stuffed our pockets with it, grabbed some jars of Potassium Permanganate, and made some nice extremely bright fires on the weekends.
After a few classes of people missing out, the teacher twigged and cut it up herself and handed us each just what we needed for the lab, no more...