Watercolor Fade Test
Create a swatch panel for checking out the lightfastness of your watercolors.
Supplies
Watercolor paints
Watercolor paper
Brushes
Backing (optional)
The Sun
Arrange Paints
Arrange your paints in the desired order. The left picture shows the way these came in the box. I rearranged them to be in ROY G BIV order. As I'm sure any painter knows, that's an acronym for the color spectrum. And since I'm color-blind (odd for a painter, I know), this is crucial that I know where I'm getting my colors from!
Red
Orange
Yellow
Green
Blue
Indigo
Violet
Note: Browns are in the Orange family so the Burnt Sienna is placed there. Unfortunately this set didn't include a purple (Indigo/Violet). I'll be able to mix those from the primaries, of course. Black gets set off to the side at the very end.
Create Two Identical Swatch Panels
Figure out how many spaces you need and create compartments on your paper. Make two because one will be the Control and one will be the Fade Test. Also be sure to use the same kind of paper (the same sheet, if possible.)
Note each compartment with the color you will be placing there. Mark one panel Control and the other one Fade Test.
(Optional) Attach each panel to a backing board if desired. Use Photo Mount spray if you have it because a glue might affect the paper if it soaks through.
Create the Color Swatches
On each sheet, create the color swatches in the order of your paint set. Use straight from the tube or thick mix from a cake/pan. Leave the bottom half of each compartment blank to allow for a wash.
Create the Washes and Lift-outs
Create a wash by drawing paint down into the bottom half of the container, using a brush loaded with clear water only. This will help you see how a lighter application of paint will hold up.
Create a lift-out by lightly scrubbing the side of the swatch. Don't damage the paper by scrubbing too hard. Lift out that little section with a paper towel by dabbing only, not rubbing. This shows how well the paint you are using will lift off the paper.
Do the Fade Test
After they are both dry, set the Fade Test panel in the sun. Just putting it in a window might reduce the full UV effect so put it outside in full sun if possible. Just make sure it doesn't get rained on or you'll have to start over!
Take it in at night if there's a chance of morning dew, fog, or other moisture effects overnight.
I like to set mine out for a minimum of five days. This will give you a good idea pretty quickly if your colors are fugitive (will fade quickly) or more permanent.
Keep the Control panel inside, face-to-face with another board or inside a paper pad so no light gets to it at all. You won't need to expose it again until the Fade Comparison.
Compare Panels
When you're ready, compare both panels. Probably within only a couple days you might be able to see some difference already, especially with cheaper paints. More expensive, "Professional" or "Artist" paints will likely have little to no fading at all.
Note: Pictured is a previous comparison I made of a relatively cheap watercolor pen set. You can see the drastic fading of some colors, which I'd never want to use in a painting. Note the blues in row four and the pinks in row five on the Fade Test panel. Who knows if the buyer would have it exposed to sunlight from a window, even for a short time? I consider those pens to be basically useless. Give them to the kids for their projects, or set them aside to use them as temporary markers, but remove them from your set so you don't forget.
Conclusion
You can set up an Indoor Test by creating another panel to see how the paints hold up under normal light exposure indoors. Good luck, and Great Art!