After reading James Gurneys blogpost about light-fastness, and www.handprint.com ´s scary tests, I decided to do my own. Since I never glaze (so far) I'm more interested in how Alizarine behaves in mixtures, rather than on its own. So that's what I did.
Aliz. Crim is notorious for being fugitive, as in it will fade to nothing under direct light. Most pigments have a light-fastness rating of 1 or 2, (pretty good) but Alizarine has 3 (Pretty bad) according to the ASTM (American Society for Testing Materials) Since its such a lovely pigment we keep on using it.
There are alternatives, like the Alizarine Permanent that I'm trying out, but instead of being a single pigment color like the regular Alizarine, it consists of 3 pigments, which in theory should muddy up your mixtures faster. (The more pigments you mix together, the faster it will turn to brown, and if there are already 3 pigments in your one tube of paint, well then you have fewer mixtures to make before you go brown or grey. Not that theres anything wrong with that, but I like to make that choice with my own pigments! Preferably, all your paints on your pallate should be single pigment paints for just this very reason)
I had a tube of Alizarine Crimson Sennelier, and a tube of Permanent Alizarine by Gamblin, which is what the famed Richard Schmidt recommends using. They are going head to head on this board coated with Galeria Acrylic gesso. which in turn was coated with a thin layer of Liquin, an alkyd dryer made by Winsor Newton. the Viridian is from Rembrandt, the Titanium white from W&N, and the Blue from Gamblin.
After the swatches were dry, I placed a thick black paper strip and taped it down with some acid free tape, to assure that no sunlight will penetrate and get to the hidden layers. I then place the board in direct sunlight. I will put the board in a plastic transparent bag, and just leave it outside throughout the summer.
You can read on the boards what colors and brands I'm using.