Sunday, September 16, 2012

OBJECT #16: Moiré cards (Mwah-ray)

    These cards have been lurking in various places in my basement for the better part of twenty years.  They’ve moved from drawer to drawer, with cards lost in some inexplicable way during each move.  (Children under the age of 10 might have had something to do with the missing cards, but then again, perhaps not.)  The battered box finally ended up in my big brown curiosity cupboard (which in and of itself is a notable piece of junk in my basement — one of those things you pick up cheap at a garage sale when you are just starting out in life and can’t afford to buy anything decent, and then years later there it is, still with out, such a permanent fixture in the house that it doesn’t even cross your mind to get rid of it.)

    The name moiré  is most recently from French, though the word has a complex etymology and was borrowed back and forth between French and English over several centuries.  Linguists speculate that the word originally came from Arabic, “mukhayyar,” meaning “chosen.”  What was chosen was the very best wool threads from an angora goat.  These hairs were woven and pressed into a fabric that the Europeans later perfected into a textile they called “watered silk.”  The hairs were aligned into a grid, then pressed into place, perhaps something akin to making felt.  The finished effect was a textile that caught the light strangely as it moved, making shimmering patterns.  (I guess if you couldn’t attract the gentlemen’s eyes naturally, you could always wear watered silk and make your yourself visually irresistible!)

    The moiré effect is now considered to be part of the world of physics, not fashion.  The most common place you’ll see this phenomenon is on a tv screen.  If someone is wearing clothing that has a strong grid-like pattern of some kind, the pattern will interact in a strange way with the physics of putting the image onto your screen, causing an effect that can be either fascinating or irksome, depending on how long you have to sit and watch it.  I’ve seen shirts and ties do spectacular moiré performances.  They produce shimmering and shifting patterns that are so eye-catching you can hardly concentrate on anything else on the screen.
    The moiré  effect is extremely simple.  It’s just two patterns, even as simple as two basic grids, laid on top of each other.  The top one must be transparent so the bottom one shows through.  As you slide one of the grids back and forth, you can see the lines of the grids shifting their positions relative to one another.  For a fraction of a second, the grids might be perfectly aligned, then a split second later, some of the lines shift to the right or left or even diagonally.  Your eye records these constant changes, and perceives it as an optical illusion of shimmering movement.

    I have a sheer white curtain on one of my windows that does a moiré  effect once in a while when the folds overlap.  I stumbled across a piece of fabric at a store a few years ago that had such a strong moiré  effect that I decided to turn it into a simple science exhibit for my traveling summer science museum.  I used replacement screen panels and put this fabric into them.  The two moiré  screens hang back to back and the visitor can move them back and forth to create stunning visual effects.

    I hope the little video here can give you an idea of amazing this effect can be when made to be large scale.  Someday when I have a permanent facility, I’ll have a huge moiré  of these that can entertain visitor on a large scale.

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