This post contains my lightfastness charts and some comments.
Left: The the control (left, labeled "in" because it was filed away out of the light) and the exposed (right, labeled "out") test sheets for Stabilo Tones. Most colors held up much better than I had feared. The first color, a magenta, lost a little vividness. The fifth color, an Indian Yellow, lost all the red, clearly seen by comparing the wash out of the two samples. The fire-engine red at the bottom of the list also lost all its depth and remains only a washed out pale magenta.
Everyone who reads my blog knows I'm a huge fan of Stablio Tones. These are a now defunct line of at least 60 colors which have been reissued in an 18-color range called Woodys. They are a fat wooden pencil which encases a wax watersoluble crayon. And they are a whole lot off fun to sketch and "paint" with. If you search Stabilo in my blog's search engine you will find many, many posts with images I've created using Stabilo Tones and tips on how I use them dry, wet, wet and dry, rubbed, etc. (Speaking of Stabilo: Stabilo Tones, Now Defunct or Are They? is a good place to start.)
Well the thing is, even though my 60-color set is wearing out (and my favorite colors aren't replaceable—as they have not made the transition into the Woody line) I couldn't find a lightfastness test chart on them in my files. I usually do one.
Right: Color tests for Caran d'Ache Neocolor II. Left, labeled "in" is the control. Right, labeled "out" was exposed. Most
colors held up much better than I had feared. My favorite color (second
from the top) is a periwinkle blue which sadly lost almost all its
reddish tone and ended as a rather bland pale blue. All the reds and brown also lost some of their vibrancy but the shift was very subtle. Again the golden yellow was a problem. You can see an arrow marking it at the base of the chart. It completely faded away.
I also use Caran d'Ache Neocolor II, another watersoluble wax crayon, though it isn't encased in wood. The two brands also have slightly different working capabilities and qualities, and even though the Stabilo Tone has reemerged as a children's art tool I prefer it to the Neocolor II. (Finger blending with the Stabilo Tone is much easier.)
I decided to do a lightfastness test chart for some of my favorite colors to have a look at what would happen over time. Also I've recently purchased Caran d'Ache's NeoArt sticks which are supposed to be an artist quality pigment stick (watersoluble wax again), and wondered if I would be phasing the Neocolor IIs out of my repertoire. Things have been too busy for me to work with the NeoArt sticks but I'll let you know how that goes.
Based on the results, by which I was pleasantly surprised, I'm going to continue to use Stabilo Tones in my journals and in my mixed media artwork as well—though there will be some colors that I will avoid using. As for the Caran d'Ache Neocolor II line I'm still up in the air. Because I like the working qualities of this stick less than the Stabilo Tone, if I find that the NeoArt line works well and has good lightfastness ratings I probably will phase out the Neocolor IIs.
A note about color test cards:
A question came up in the comments section about my labels "in" and "out" on my test cards. "In" is the control that was filed away, safe from light. "Out" was the card that was exposed to the light. Both cards are made on the same day so that you can compare the change from that day caused by light exposure. I actually make my test cards on the same sheet of paper as well, making two identical vertical lists of colors, using the same hand pressure, making the density of the pigment as uniform as I can. Then I wet and wash out each sample because washes show another aspect of how this medium is used and I want to see how the light will impact the washes. (It is often easier to see which "portions" of a paint fade in the washes, e.g., a lavender blue fades out to a simple pale blue you know the magenta originally in that color was very light sensitive and has faded.) When the test is completed I scan the tests and save a digital file and I file both cards together in a folder with other media tests.