Radioactive Ink
Radioactive ink is made by mixing a small amount of 32P with waterproof black drawing ink. We find it convenient to make the ink in three grades: very hot (>2000 cps on a hand-held minimonitor), hot (>500 cps on a hand-held minimonitor), and cool (>50 cps on a hand-held minimonitor). Use a fiber-tip pen to apply ink of the desired activity to the pieces of tape. Attach radioactive-warning tape to the pen, and store it in an appropriate place.
