Ink over time

Recently I started writing with a fountain pen again. The appetite for fountain pens has been ignited by the cheap Preppy. The sensation was quite nice switching from ballpoint to fountain pen. But the fact that ink is soluble into water made me contemplate on the resistance of ink over time. You can find on the Internet and on the forums good UV tests of different inks. But I wanted a test of my own to see how my inks work in my situation, so your  mileage may vary. I live in a place with moderate sunlight. I tried to replicate what would happen to your ink writings left on a table on which you get a fair share of sunlight.
The test is not very scientific as i used different fountain pens and the exposure to light was different as i did not used all the inks in the test from the begining but still the results are interesting.

Inks used: platinum blue black, Faber Castell royal blue, Faber Castell permanent black, Pelikan 4001 royal blue, Pelikan 4001 black, Pelikan 4001 personal mix 1:1 royal blue and black, Koh I Noor Blue

The test was conducted for a period of 4 months from March until June.

Results:
Koh I Noor blue with the least time exposed to sunlight is almost invisible
Faber Castell royal blue is very hard to read even though it received a similar amount of sun with Pelikan 4001 royal blue
The blacks from Pelikan and Faber Castell look similar after sun exposure.
The winner of the test I would say is the Platinum blue black
The ink was not the only one affected by the sun the paper that was exposed obtain a yellowish tint

Also see: Platinum Preppy