Wednesday, July 13, 2011

Pigments of My Imagination

I got sidetracked by vacation and few other things and lost my way regarding the chemical elements. The following inorganic pigments are mostly familiar.



Red is for red and white lead in striped lighthouses and also miniature manuscripts. The red color comes from lead tetroxide and the stark white comes from lead carbonate. Both pigments are impervious to the elements which is precisely why Michael Faraday chose them to coat Britain's lighthouses.
Red is also for Barn Red. Farmers in Europe started this tradition by adding ground up rust to the linseed oil they used to protect their barns and sheds (the iron inhibits mold).

Orange is for terracotta roof tiles: The color comes mainly from iron oxides.

Yellow is for yellow school buses.  Originally the pigment came from lead chromate (the color comes from the chromate, not the lead). It too was impervious to the elements. Lead chromate is no longer used to paint buses, but the traditional color stuck with us.

Green is for emeralds. Beryl and emerald are essentially the same material, viz., Be3Al2Si6O18. The only difference is that emerald also contains about 2% chromium, the source of its green color. Chromium also makes rubies red, and sapphires blue.  How does the same element do that?

Blue is for the Prussian Blue. I wrote about this back here. Gun bluing, a form of metal passivation, is another iron coating in disguise. Blue is also for cobalt blue.  As the saying goes: if it's blue, it's cobalt (II).

Indigo is for itself. Its color is challenged by some as a separate distinct color: link The most vivid indigo colors I ever saw were solvated electrons trapped as either sodium electride or as sodium benzophenone. What do electrons really look like? link

Violet is for purple permanganate, KMnO4 which is actually pinkish purple but I couldn't think of a better example. Can you?

9 comments:

  1. Didn't purple come from beetles?

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  2. I think you're onto something Carol: link.

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  3. You may also have shellfish notions: Tyrian Purple.
    Interestingly, that color had to be extracted from living organisms and this doesn't qualify as a robust, colorfast pigment like the others here.

    Organic dyes are whole 'nother thing. If you got me started on those, I wouldn't know when to stop.

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  4. What about coal?

    "Mining" seems to go back to the stone age. What if soft coal were found? In the beginning, it would not have been used to make fire.

    The first "paint" applied to a face?

    When time goes back, and you see the cave paintings, what was the artist using for his sketches? Why not coal? That would give you black right there. And, a chance to mark spots on rocks with your "X" ... in case you wanted to go "far" ... and then find your way home?

    In Tom Sawyer, there's a cave scene, or two. And, the known part of the cave got marked with candle fire. Holding the candle up to some upper point in the cave ... even gave people the chance to write their initials. (The cave gets covered. Injun Joe dies inside.) A whole part I didn't remember.

    Sure. If the ground were soft enough ... and there was sunlight ... you could use a twig from a dead tree ... to mark things out, too.

    Big disputes arose over territory. Because that's just human nature.

    I hate to think what they did with their kaka.

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  5. Coal is a fascinating substance Carol. It appears black because it absorbs all visible light, leaving no rejected wavelength for us to color it with a name.

    Graphite is closely related to coal. It appears (and behaves) metallic. When a huge cache of natural graphite was found in olde Britain they used it to mark sheep. They called it "plumbago" on accounbt of how it looked. So they really put the "lead" in pencils.

    When Lavosier proposed that diamond was carbon too he had to burn one to make his case.

    You're getting me real interested in listening to (as opposed to reading) Mark Twain's stories. You may have already suggested some recordings but where would you start again?

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  6. GROVER GARDENER! He's the best voice in then entire audio recording industry!

    My son noticed this. I did not. But after he told me, then I began plugging in Grover Gardener's name at Amazon.

    If I'm not mistaken, he recorded the autobiography that just came out. It's astonishingly long. But his voice is pure butter. Or velvet.

    Since I've never read Huckleberry Finn. And, my son wants to me. (For some reason I avoided this one.) I'm going to go to Amazon and buy the audio recording.

    So, you could start there?

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  7. Oy. I misspelled GARDNER. But I pulled the audio from my collection. It's 20 CD's long. And, it is only Volume 1. (There's more to publish.)

    So, now I'll be on the lookout for Manchester's posthumous Churchill. Volume 3. And, Mark Twain's autobiography. When Volume 2 comes out.

    You can't go wrong.

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  8. Sure. If the ground were soft enough ... and there was sunlight ... you could use a twig from a dead tree ... to mark things out, too.

    Did you know that if you wrote a contract or statement in the sand with a stick, signed and dated it & then took a photo of it and presented it, the US Patent Office would accept it as legally binding.

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  9. No. I did not. I think by the time I ran the stick thru the sand to spell my name out ... half of it would have been covered in sand.

    And, then, what lens would you use on your camera?

    Tom Sawyer is full of blood oaths. Stuff between him, the Harper kid, and Huck Finn. Was always sworn to. Sometimes at the cemetery. (And, they saw the good doctor murdered.) So before "oaths" get to the patent office ... they were between boys of about the age of ten. Who took them very seriously. So spoketh Mark Twain.

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