[freosam]

> This boils down the difference between pigment and dye based inks. Dye based inks are more expensive but more resistant to UV light.

I think it might be the other way around: pigment-based inks are opaque particles bonded to the paper, and so even if their colour changes/fades they're likely to still be legible. Whereas dye-based inks, when they fade, can completely disappear. (One advantage of dye-based inks is that they have a larger gamut.)