Fading Marker Ink: What's Happening?

[Lim Y K]

I used Colour markers to write on a piece of paper and pasted the piece of paper on the wall. After a few weeks, I noticed the ink faded, or rather, became very faint that the words were almost illegible. Can anyone explain to me this phenomenon scientifically? Thanks

 

[DrClaude]

UV light is breaking the bonds of the molecules responsible for the color. Inks have color because they contain molecules (dyes) that absorb part of the visible spectrum, such that the reflected light doesn't appear white anymore. The downside is that these molecules are often also good absorbers of UV light, and they will degrade rapidly. This is especially true of red inks, which have to absorb in the blue-violet part of the spectrum to appear red.

 

[Borek]

The answer given by DrClaude is the most likely one, but some airborne substances can also decolorize inks. For example if you were to put your notes close to an open bleach bottle I would expect the ink to fade even in the dark. I doubt that's the case, though.

 

[CWatters]

Just for info...Pigment based inks typically fade slower than dye based inks.