Zowie. On the 19th I put half the color swatches outside each day in full sun. And today I put the two pieces next to each other to see if there was any fading. And boy was there! Opera Pink is known to be fugitive (fades) and you can see how it's still bright pink on the indoor piece (upper half) but the outdoor one now looks red/magenta. No real pink in it. But shockingly, and weirdly, the Antwerp Blue has faded like CRAZY! I was so surprised that I put a couple of new dots of Antwerp and also of Prussian Blue (same pigment) on the card. I want to see if they follow suit or if somehow, someway there was something odd happening with the Antwerp from the first trial.
Important information? If you want to be sure your paintings don't fade away, you bet it is!