Tech Talk: Lightfastness tests – 5 months

full view of my test card –

sun-exposed half on left

center panel compares full-strength color –

sun-exposed paints to left of center

center panel compares tints (diluted washes) –

sun-exposed paints to right of center

Back in January of this year, I began a lightfastness test of these Mission Gold watercolors after receiving some samples of the paints. Because they are new to the market, there were no published lightfastness tests, and many of the pigments used in the manufacturing of these paints were poorly rated in the resources I have.  (See my previous posts here (introduction), here (at 2 weeks) and here (at 6 weeks).)  I put half of the sample sheet in a folder made of acid-free matboard and stashed it in my flat files.  My sun-exposed half of the test sheet started out with several hours of winter sun each day, but at this point, the sun is blocked most of the time by trees.  I've now moved the sample to a spot that gets sun for about 4-5 hours most mornings and will continue the test for about six more weeks.  However, there are such clear changes at this point that I would be remiss in not sharing the results.

I took these photos in full sun yesterday and have done a bit of digital cutting and pasting on the second and third images so you can more easily see the comparison of the full-strength pigments and the tints. (Note that the sun-exposed pigments are on the left side of the full-strength sample and on the right side of the tint sample.)

I should point out that pigments ranked as lightfast on some lists may indeed be lightfast in other media, but unreliable in watercolor paints. As I understand it, this is due to the binding agents used -- oil and acrylic paint bases being more protective of the pigments than the gum arabic used for watercolor.

As noted in earlier posts, the full-strength Permanent Yellow Light (PY17) has darkened with exposure and it has also faded significantly in the diluted wash. Quite a predictable outcome, since the pigment is known to be fugitive.

Yellow Orange (PY65 and PO13) is composed of a very reliable yellow pigment, but also contains the same unreliable orange pigment as Orange (PO13). Both show darkening at full strength and fading as a diluted wash, although it's more pronounced in the Orange sample.

The Permanent Red (PR112) is only slightly changed at either strength, but Permanent Rose (PR122 and PR209) is quite faded both at full strength and as a tint. A bit of a surprise, actually, since Permanent Rose is a mix of two supposedly reliable quinacridone pigments. [added note: There is some disagreement on the lightfastness of PR122, with Michael Wilcox labelling it as unreliable.] The Rose Madder (PR83:1) is actually alizarin crimson, a pigment which has been replaced in most professional-quality product lines by a more lightfast substitute. This paint changed only slightly at full strength, but is noticeably faded as a tint.

Permanent Violet (PV3:1) is anything but. It began showing signs of fading by the second week of sun exposure and is now seriously changed both at full strength and in the tint. This comes as no surprise, because the pigment is a known bad actor.

All three blue paints in my sample -- Ultramarine Deep (PB29 and PV12), Prussian Blue (PB27), and Peacock Blue (PB15:3 and PG7) -- seem quite reliable, despite the inclusion of a mystery violet pigment in the Ultramarine Deep. I can find no information in any of my resources on it, but it doesn't seem to affect the color stability.

Viridian (PG7) is actually phthalo green, which makes it very stable, but also a very strongly staining paint. Sap Green (PG36, PBr25, and PY17) includes the same yellow pigment as Permanent Yellow Light, which means it shares the same problems -- darkening at full strength and very noticeable fading in the tint.

Burnt Sienna (PR101) was a definite suprise -- fading badly across the board. Not a true burnt sienna, it is composed of a red pigment that is supposed to be very lightfast, but this sample didn't live up to the reputation of the pigment. 

VanDyke Brown (PBr9) is made of a pigment that does not appear in any of my resources, but is similar to one that is rated fugitive/unreliable. It faded particularly badly as a tint -- in both samples!! I had to go back to check my photos at 6 weeks to verify that there had been a noticeable difference in the exposed and non-exposed tints at that time. I therefore have to conclude that simply exposing this paint to air will cause it to deteriorate at tint strength.

So I'm sorry to say, but my advice would be to avoid Mission Gold paints as they are currently formulated -- unless you're planning to channel Picasso's Blue Period or keep your work in a drawer.

My demo for CWA...

 

My demo painting -- next to last step

I had a great time as the guest artist for the California Watercolor Association at their May meeting on the evening of the 15th.  My husband drove over with me (their meeting spot is about 70 miles from my home), served as general roadie, and also took these pictures during the demo.  He managed to capture most of the steps along the way, although he was unable to get a picture of the last step I did during the demo.  But I'll be posting more photos after I finish the piece, so you'll be able to see all the steps after the last image posted here.

I originally had a different image drawn out (in five steps), but realized about a week before the demo that it was much too complex for a 90 minute demo.  At that point, it was scramble time so I decided to give my favorite vintage salt shaker another turn in the spotlight.  In addition to painting on this image, I talked about prepping my images, chosing background resources, and using masking fluid to save highlight areas and frisket film to protect the shaker when stamping or spattering the background.

 

Starting point

I had the body painted in before I arrived.  The main color is new gamboge, mixed with some Daniel Smith quinacridone deep gold and a little Winsor violet (dioxazine) for the shadowy areas on the base of the shaker.

Step one -- painting the head

I'm using French ultramarine blue for the main color on the head and mixing the blue with a bit of Daniel Smith's quinacridone sienna for a deeper tone to model the three-dimensional form.

Step two -- the wing is complete

Next, I painted in the wing, using cobalt green.  Because I wanted to show how the glaze on the wing bled into the body, I lightly painted a clear water wash on the yellow body so the green would drift into the yellow slightly.

Step three -- painting the bill

I'm using scarlet lake for the main color on the bill and a mix of scarlet lake and Payne's gray for the darker red that I pulled along the edge of the bill to give it form.  In this photo, I'm adding an orangy-red -- made by adding a bit of new gamboge to the scarlet lake -- to the center of the bill to give it a subtle highlight.

All the large color areas are complete

At this point, the main areas are colored in and it's time to add the black details.  I mixed up a nice deep black with French ultramarine blue and Daniel Smith quinacridone sienna and am starting to paint in details around the eye in the next photo.

Step four -- painting in the black details

Step five -- bringing the highlights to life

In the last step I have to show you, I have removed the masking fluid and am softening the edges of the highlights to make them look realistic.  This step also shows the preliminary background -- I painted a rosy purple across the background and then stamped it with masking fluid using a stamp I'd cut out of a compressed sponge.  I protected the painted shaker with frisket film (actually a transparent, low-tack contact paper that I bought at either a hardware store or drugstore).  

The last step of the demo was to pull a deeper purple wash across the background to make the stamped images pop.  Unfortunately, my husband didn't capture it with the camera.  When I finish this painting, I'll remove the masking fluid and very likely spatter some gouache on the background to soften the pattern and keep it in a supporting role to the main character.

Hope you enjoyed the demo.  Stay tuned for the final results.