[Jewelry making - Article 00007] - [Orchid] Lasers Make Other Metals Look Like Gold

[Norah Kerr]

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    I hope this isn't a repeat but it is VERY cool. I'm a little
    surprised by ~his~ surprise that we would be interested in colouring
    metal. Ummm... Heck yeah! But I am wondering how robust it is really. 


    Norah
    www.besmithian.com

        Lasers Make Other Metals Look Like Gold
        http://tinyurl.com/3d55kt

        All that glitters golden is not gold. It could be aluminum. Or
        tungsten. Or another metal of Chunlei Guo's choosing 

        In a feat of optical alchemy, Dr. Guo, a professor of optics at
        the University of Rochester, and Anatoliy Y. Vorobyev, a
        postdoctoral researcher, use ultrashort laser bursts to pockmark
        the surface of a metal in a way that is not perceptible to the
        touch it still feels smooth to the finger but that alters how
        the metal absorbs and reflects light. 

        The result is that pure aluminum looks like gold, and the
        appearance is literally skin deep. 

        "I cannot tell it's not gold," Dr. Guo said. "It looks very
        pretty." 

        Dr. Guo and Dr. Vorobyev reported their findings in the journal
        Applied Physics Letters published online Thursday. 

        The golden aluminum follows work a little more than year ago
        where Drs. Guo and Vorobyev reported that they could make gold
        and other metals look black indeed a black that is blacker than
        the usual black, sucking up almost all light that impinged upon
        it. 

        The laser bursts each lasting only about 60 millionths of a
        billionth of a second melt and vaporize metal atoms near the
        surface, which then reassemble in minuscule structures including
        pits, spheres and rods that are a fraction of a millionth of a
        meter in size. 

        By changing the length, strength and number of pulses, the
        researchers found they could vary the resulting color. 

        In some cases, the change causes the structures to absorb a
        range of colors so that they cannot be seen. But the colors that
        are not absorbed are still reflected, and thus visible,
        resulting in gold aluminum or dark blue tungsten. 

        In other cases, the laser pulses create a periodic array of
        structures that cause the reflected light to interact and
        interfere with itself, producing an iridescent, shimmering
        rainbow much like some butterfly wings, Dr. Guo said. 

        Dr. Guo imagines a kaleidoscope of potential uses, from the
        practical (a reflective filter) to the whimsical (etching the
        family photograph onto a metal refrigerator door, for instance).
        Another possibility is custom colors for bicycles or cars,
        without the need for any paint. 

        "It's pretty robust, because it's right on the metal, and it's
        not going to peel off," Dr. Guo said. 

        He cannot yet make all metals into all colors but says he
        believes that it is only a matter of trial-and-error to find the
        right recipe for each permutation. 

        With his black metal finding, Dr. Guo suggested the possibility
        of black gold rings. He was surprised when jewelers started
        calling. "They are actually indeed interested in making colored
        jewelry," he said. 

        In the new article, he suggests a blue gold ring, perhaps a blue
        to match the eyes of a fiance.
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