Color Fading

[kermit911]

Say you have a sheet of red paper, and you leave it in the window.  The sun turns the red paper pink.  What happend to the ink?  What if you laminate the paper first.  Will it still turn the red paper pink?

Thanx

[gen2]

According to my understanding (which may be faulty), there are three possible mechanisms for fading.
1)  Oxidation.  Light provides the excitation energy to initiate a reaction between the dye and atmospheric oxygen.
2)  Isomerisation.  The light provides the energy for the molecule to flip from one isomer to another and the two isomers have different colours.
3)  Decomposition.  Light triggers the breakdown of the dye molecule into two or more smaller molecules each with different properties.

I don't think that laminating plastics are totally impervious to oxygen.  Laminating the image before exposure to light will probably greatly slow down the fading process if the dye degrades with the assistance of oxygen.  It will probably have little or no effect if the dye degrades by one of the other processes.

However, laminating plastics are adding more chemicals to the equation and  another possibile mechanism for fading enters the arena.  There may be a reaction between the plastic (or chemicals within the plastic) and the dye.

What actually happens will depend upon the actual dye used and the conditions it is exposed to.  The best approach is to "try it and see".

[Hamish]

The discloroation is a process called photobleaching, wich as pen2 suggestes is a light intiated reaction wich may be between the dye and the paper or dye and the air. The reaction is faster for reds as these absorbe the higher energy blue light. Filtering out the blue/UV light will slow the process down. As many polymer absorb in the UV you will probably have some luck with lamination although there will still be some fading over time.