W&N Paint and Arches Torchon behaviour in the Sun - the 4th year!

In June 2011 I started to test the properties of Arches Torchon Watercolour paper and Winsor&Newton paint. I painted the colours Payne's grey, Sap Green, Sepia, Crimson, Ultramarine, Lemon Yellow, Winsor Blue, Winsor Red and Winsor Orange) in strokes, cut the paper in three pieces, put one in a binder, varnished one (with Schminck aquarelle varnish) and did nothing to the third.
Then I stuck the varnished and untreated parts to a window on the South, where the sun is practically always shining (and it is a bright hot sun: I'm in the South of France).
Last year (2014) the Alazarin Crimson was definitely a bit paler and also the Ultramarine seemed to be a bit lighter, especially on the un-varnished part.
This year, if I squint, it looks as if both parts (left and right) that have been in the sun (for 4 years now), are slightly lighter than the part (middle) that hasn't . But it could just be the photo...
We'll probably see next year, because they're back on the window!

The varnished part also seems a bit better. In the picture below, the top one is never in the light, the middle strip is varnished (and seems slightly darker) and the bottom strip is unvarnished.
The paper (Arches 300grs torchon or rough grain) hasn't changed colour after 4 years by the way.

We can conclude, not very surprisingly, that it is best to keep your watercolours in a dark spot. And that the least permanent paint takes 3 years to start going pale. And that W&N Alazarin Crimson is the least lightfast - of the tested colours.

I'll soon start with part two of the research: other brands, other paper...
More next year!!