Carcenomy wrote:Some of these cases have taken decades to yellow, my question is if yours have yellowed like this in four years in darkness, how much more would they have yellowed in a normally lit room? Is it a constant level of yellowing regardless of exposure?
Yes, I don't think light plays a factor in this case. The bromide molecules causing the yellowing now were formed when the unit first yellowed. It's just they were deeper than the surface layer so Retr0Bright didn't deal to them. But you couldn't see them hence it looked like all the yellowing was gone. However, over time those deep degraded bromides made their way to the surface and lo and behold the surface was yellow again. Light wasn't needed or UV. Heat probably helped their progress as the computer room gets pretty hot in summer.
This is what I think happened, and it seems to fit what is known about yellowing and how those bromides behave in plastics.
The more yellowed a case is, the deeper those bromides probably are so the more like the case is to regress after retr0brighting. If the theory is right, another session of Retr0bright should make the cases white again....for a while. Then you might have to do it again...and again. However if you kept the case out of the sun/light so there was no NEW Bromide degradation then eventually all the bromides that formed in that initial yellowing might be out of the case, and it then might be permanent.