Update on the Copic Fade Test

As I've noted before, I have had a test piece of a Copic marker drawing in my window since July 15th. The window is north-facing, so it doesn't get much direct sun, but gets lots of ambient daylight. The lower half of the page is in a folder away from light as a control.
Now at the 6-week mark, some shift in the inks is visible. There is minimal change in the lighter values, and not much in the warm grays overall.
The big change is in the black test strip- it is now markedly lighter than the control, meaning that a drawing done exclusively with it would more quickly start looking `washed-out'. The 90% warm gray is on the edge, but not nearly as much.
Different colours are made from different dyes, and each will behave differently. Black dyes are notably weak - Sharpie markers, for example, fade easily with light exposure. The warm grays may have much better permanence. If the darker values include some of their black dye in the mix, that will alter more. I'm glad I mostly use pigment-based pens for blacks, like the Sakura and Pentel brushpens - they won't fade.

Putting a drawing in a window is more extreme than ordinary hanging situations. My guess is that this is 3 to 4 times more direct light than hanging on a wall. So I would say this is the degree of change one would find after 5 or 6 months on a wall that doesn't receive direct sun. Slight, but there. The change is subtle too - as a drawing ages on a wall, fading wouldn't be noticeable for a long time
The test continues.