Also, if you want to get high tech, use a fluorescent dye mixed with DMSO. It'll penetrate deep into the skin, and be visible under UV (no cosmetic objections). I suspect it'd take weeks to wear off.
Can't imagine mixing dye with DMSO -- if you've ever played with DMSO, you'd know that putting a little anywhere on your skin brings it into your mouth, and everywhere else in your body, within seconds. You can taste it almost immediately, and any chemical combined with it is also carried throughout the body, which is often not a good idea. But the dye-dipped finger is a good idea, which would also negate the need for those little "I voted" badges. -- Harmon Seaver, MLIS Systems Librarian Arrowhead Library System Virginia, MN (218) 741-3840 hseaver@arrowhead.lib.mn.us http://harmon.arrowhead.lib.mn.us