Now you see it …

Hide and Seek Technologies of Nederland, Colorado, last year announced its
plans for a digital video disc that would self-destruct after a few plays
(This Week, 15 November 1997, p 7).
At the time, the company would not say how it
works, but now a US patent 5815484 explains all. The disc includes an extra
layer made from what’s called a “spiropyran” dye, which gradually darkens as the
disc is played. Eventually, the dye obscures the signal on the disc. Hide and
Seek sees this as a way of renting out disposable video discs that needn’t be
taken back to the shop.