forgot it was in 2004 or even earlier, an American com debut a special DVD disc which only can last few days after you opened the package. $ is about the cost you pay for BlockBuster renting fee, but you don't need to return the disc since it's no longer useful.

now this disc is released in JP, called 48DVD.

in factory sealed package, it can last whole yr fresh status. once you opened it, disc starts chemical changing from red to black. before it's dead, you can playback as many times as you want. in real test, it last more than 48 hrs. you still can playback movie in after 60hr. but when it's 72hr, movie playback is a problem, paused, mosaic, unsmooth.....

so they did another test to extend disc lifetime.
b/c such special chemical coating on disc changes after exposured to air. if can isolate air, disc life may be extended. they put disc into water...... result is....... you have to try it by yourself to find out.

you can see its color changes from original red to black, in 24/48/72 hr.
244872