If you scan the cases with light at different frequencies, you can make the ink glow and thus see under the paste and plaster that would normally obscure the text. A lot of the writing is unspectacular (the BBC describes them as shopping lists and tax returns), but that's the point -- it's about discovering Egyptian history beyond royalty and other famous people.

The technique has already found success with one mummy stored in Kent. It's not certain that it'll find widespread adoption, but it's hard to see historians turning this down. Much as with techniques used to read closed books, this lets researchers have the best of both worlds: they can read 'secret' text without having to sacrifice priceless relics.