Acid-Free plastic storage bags

Why does storing your photos in plastic storage bags slow down the fading and discoloring process? From

what I already know the ink evaporates off the photo paper but sun can also fade. So why do these bags

help?

I don't know. But if the bags are airtight, my guess would be keeping out atmospheric contaminants (ozone, cigarette smoke, etc), as well as keeping changes in humidity to a minimum.

A lot of dyes fade with UV so it may be that the plastic bag filters out some of the UV and reduces potential fading.

I wouldn't rely on the plastic bags to inhibit fading from UV exposure, but they are great for protecting prints from minor abrasions and atmospheric pollutants - especially if you live somewhere like LA, Denver, NYC, etc. The only way to avoid fading from UV is to keep the print out of direct sunlight at all times or, if you can't avoid that, frame it behind glass that filters UV.

The wrong kind of plastic will actively damage your prints. Don't improvise. The wrong kind of plastic is worse than nothing. Nothing's great, as a matter of fact. If you want to get fancy, interleave with acid-free paper.

 

Ink doesn't evaporate, only the ink's solvent evaporates.