Wednesday, January 30, 2013

Tech Talk: Pigments – Week 2


 Lightfastness -- comparing full strength paint
(bottom half is sun exposed strip)
 

Lightfastness -- comparing tints
(top half is the sun exposed strip)

Two weeks ago, I began testing these Mission Gold watercolors. (See the original post here.) After painting the test strips, I cut the page in half and put one piece in my flat files and the other in a spot that would get direct sun. Following my plan to compare the sheets every two weeks, I put the two pieces together today, first comparing the full-strength strips and then the lighter washes.

There are a few changes at this point, although nothing drastic. As might be expected, the tints (light washes) were generally affected more than the full-strength colors.  Prussian blue faded slightly in the tint, as did burnt sienna -- both a bit of a surprise, since the pigments listed on the tubes are supposedly lightfast.  There was also a slight darkening of the yellow, particularly noticeable at full strength. The tint of Van Dyke brown faded slightly.  Neither of these was unexpected -- the yellow pigment was rated as fugitive by both Michael Wilcox and Hilary Page and the brown is unlisted, but its closest relatives are considered fugitive.

It's worth noting that the sun-exposed strip has had only a few hours of sun a day on the best days and we had 4 or 5 days of deeply overcast weather in the past two weeks. I'll continue to monitor the test strips and will post again when there is more information.

6 comments:

  1. Hi Chris, This is an important experiment for pigments in all media. I've found that Alizarin Crimson is very fugitive compared to many other pigments, but will interested to see what you discover. Thanks for this post!

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    1. How nice to hear from you, Kathy!!

      Indeed, though beautiful, Alizarin Crimson is not a reliable pigment. The replacements created by various paint manufacturers are more reliable but don't reproduce all subtleties of A.C.

      Some pigments that are fine in oils or acrylics do not perform well in watercolor. (The oil and acrylic base materials apparently offer better protection against fading.) So it's important to check a pigment's suitability for watercolor specifically, rather than relying on a generic evaluation.

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  2. Chris, I find this fascinating that you're doing this:) Have you met James Toogood? I consider him the Alton Brown of the watercolor world (he is obsessed with the science behind everything). I'll be following along with you to see what happens.
    Carrie Waller

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    1. Hi Carrie -- glad you're in touch!

      I've not met James Toogood, but I've had a longtime interest in this subject, predating the blog world. Figure we can't be too careful when we put half a zillion hours into a painting!! ;-)

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  3. Chris, I am following this closely and you know why...can't wait til it's a bit further along. Patience, patience...
    thank for doing this. It will be very interesting to see how these pigments hold up!

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    Replies
    1. Hi Frank -- nice to hear from you!!

      It is definitely an exercise in patience -- I don't have a spot that gets more than a few hours of sun a day and there weren't any additional changes noticeable when I compared the two strips for the second time (after 4 weeks). I've read that it takes 6 weeks of full days of sun exposure to see fading, so it may be months at the rate I'm going. I'll report when I have further results.

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