My new Ultimate spider-man #1 had a tear on the spine, so with this thread in mind, I put it in a cheap bag and board (from a Midtown order) and put it in my window of my comic book room inside the blinds, so it is always exposed. Faces north, so gets light all day, some direct sun, some not. Placed it on Mothers day, and will scan it every so often for several months to see how it does. May not be scientific, but certainly 'real world'.
So far, about 234 hours of natural light, a good deal of bright sunshine, and no noticeable fading. I set it next to another copy from my boxes, and couldn't tell them apart. I am feeling better about having them in my dark room on display with only a few hours of LED light per month!
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5-10-14
5-16-14
5-28-14