Color Primer, Part 1b

Hibernation is (almost) over: dissertation is written, approved, and submitted for graduation–which means I can get back to the business of keeping an active blog! For those of you who have patiently waited, checked back, and waited a bit more, thank you. Really. There are never enough hours in a day to take care of a full “to do” list, but now that my dissertation is completed, I can focus more time on sharing the research.

Almost over, because I am about to go on the road and will have little/no internet access for the next two weeks. I wanted to get back to why yellow quills, for instance, look yellow instead of blue. Since it’s been so long since the last posting, I thought it might be useful to fill this “almost” gap with a quick recap and a couple of web links for additional information and foreshadowing.

In the last post, we established, in the most general sense, that objects are colored because of the ways in which that object interacts with light. Specifically, a yellow quill looks yellow because the quill reflects those wavelengths of light associated with yellow, and absorbs the rest. It has just occurred to me that it might be helpful to have a visual of what wavelengths are associated with which color (red, yellow, blue, etc)….rather than re-invent a perfectly good wheel, I’m going to direct you to this page, What Wavelength Goes With a Color? from NASA’s Atmospheric Science Data Center:

http://eosweb.larc.nasa.gov/EDDOCS/Wavelengths_for_Colors.html

Part 1 ended with the promise of looking at how the structure of the various colorant molecules dictate the color observed when dyeing with that material. There isn’t a one-size-fits-all answer, exactly, but there are a couple of models that can be used to explain the contribution of molecular structure to color. What will follow in the next post is a discussion of these models based in part on material from Mary Virginia Orna’s 1998 book, Chemistry and Artists’ Colors. It’s not necessarily the easiest book to find, but well worth the hunt if you’d like to know more on the chemistry of artists’ paints. A more physics-oriented presentation can be found in Kurt Nassau’s The Physics and Chemistry of Color: The Fifteen Causes of Color (this one will give you the chemistry behind pigments like lapis lazuli and gemstones like rubies, too). There’s also a web site on the causes of color,

http://www.webexhibits.org/causesofcolor/0.html

Finally, at the risk of stating the obvious but to make sure there’s no understanding, I’m interested in organic dye molecules–those made primarily of carbon, hydrogen, oxygen, and nitrogen atoms–as opposed to inorganic pigments, which in the simplest sense tend to contain at least one metal atom like copper or iron. So if you start flipping through a copy of Orna’s or Nassau’s book–or check the webexhibits.org link above–and want to focus on the most relevant content with respect to this blog, stick with sections on color in organic molecules.

And if you also don’t have enough time in your day for extra homework, no problem! The next posting will be mid-May, and will dive right in to where Color Primer, Part 1 left off.

Advertisement