Well you could store solagraphs in a light tight box and view them under safelight. The one that was posted recently on apug and elsewhere was destroyed as he decided to scan the image in. The bright light strip from the scanner obviously destroyed it.
The impossible project used to have a product called fade to black where the Polaroid does exactly that. The image goes totally black within minutes or hours.
I would also checkout different brands of paper. Each reacts a bit differently to light when not fixed. Some have different hues that appear, others go darker when hit with a light source. Good luck