ASTM standards: Make sure the paint you are buying has a ASTM rating on the label. Most quality brands like Sennelier, Schmincke, Weber, Daniel Smith and Golden's to name a few, have that label on their paint. Some, like Daniel Smith, have colors made from minerals, like their Primatek paints, that are not ASTM rated or tested, but do their own lightfast testing and give you their results. The info on the label needs to contain that ASTM rating and a lightfast rating so you know how well that color will stand up to fading over time. Pastels are one medium that do NOT have an ASTM rating because there are NO ASTM standards as of yet for pastels, though they are trying to establish one.
If there is no ASTM rating on a tube of paint or a pastel you are using, you can run your own tests just by painting swatches on a surface you would normally use. Cover one side of the swatch so light cannot penetrate and leave the other side uncovered. Leave it in an area that gets direct sun and leave it sit for several months. Go back to it at a later time and uncover the covered side to see if there was any fading of the uncovered side. There are websites that go into this test in detail and much more scientific, such as http://handprint.com/HP/WCL/, but this is a pretty basic way to test the lightfastness yourself.
Stay away from student grade paints that aren't as heavily loaded with pigment (to keep the costs down) or even the correct pigment, some, to cut costs, will say something like "Cobalt Blue Hue." If you see the word "hue," read the label and read up on your pigments. The Cobalt Blue pigment is PB 28. It's usually an expensive tube of paint so if it's cheap, says HUE and is not PB 28, then you aren't getting the real McCoy. This also goes for mixes, colors like Sap Green are made with different mixes of pigments, depending on the brand. So if you like one specific brand of Sap Green, check the label first on another brand because you might not get the color you are looking for in the other brand. Learn your basic pigments!
When you purchase artist materials, you want to create art that's going to last your lifetime and beyond, right? Read labels, use quality materials and read up on materials. One good source for materials is Michael Skalka's articles in The Artist Magazine and he also writes the "Grammar of Color," which is a goldmine of information about color and materials. Michael is the Conservation Administrator at the National Gallery and is the Chairman of the ASTM division of Artist Materials. You can search for his articles on the web.
