Once again my son, who is now in tenth grade, suddenly had to have a science fair project right away last semester, so I suggested a dye-related topic. He was happy to take the idea I suggested rather than having to think up something new in a hurry. It's handy to have the dyes and chemicals and stuff already in the house, plus plenty of good reference materials on the shelf. What he studied was what different protective treatments helped the sadly light-sensitive dye Procion Blue MX-7RX, plus, for variety, Procion Orange MX-2R, in surviving exposure to the sun. His results were a little surprising. It's due this week, so here is the graph he made this weekend of his results:
Nothing really helped prevent blue MX-7RX from fading, except for storage in the dark. Picture framing glass didn't help; low-E UV-filtering window glass didn't help. The ultraviolet protection spray he used, Granger's Tent and Gear UV waterproofing, didn't help a bit. Surprisingly, Rit Sun Guard (which contains Tinosorb FD) did provide a little protection, but not enough to make any real difference. It looks as though it is just blue, violet, and a little ultraviolet-A light that causes the damage to blue MX-7RX on cotton. Treatments that absorb ultraviolet B waves do not help at all.
Here's the photos of the fabric before and after sun exposure (not counting the samples that were stored in the dark):
It would be interesting to see how much of a difference dyeing silk instead of cotton makes. Deborah Harowitz of the Scarlet Zebra found it to make a significant difference!
My son did not see enough fading of the Orange MX-2R to really be able to tell if anything helped. Glass was better than nothing for that dye.