©1996 William Beaty

Once you become "sensitized" to the scratch hologram effect, you start seeing it everywhere. It gets to be a pain, because soon you won't be able to NOT see it! ;)

When vinyl record albums or CDs are illuminated by a small light source, a 3D stripe of light is seen. Go outside in the sun, hold the disk at waist height while facing the sun, look down at the disk and tilt it back and forth until you see a bright stripe of light on the disk. Notice that the stripe isn't really *on* the disk surface, but instead seems to tilt down into the surface of the plastic, in 3D.

Brushed metal knobs on audio equipment display radial stripes of light, as do brushed metal wheel covers on cars. When illuminated at the proper angle, these stripes will appear to dive inwards in 3D. One part of the stripe floats within the surface, the other part juts out into space. The concentric circle-scratches form a hologram of a tilted bright line.

Observing the windshield of a car driving at night, streetlights shine through the fine concentric windshield wiper scratches on the windshield. They create bright stripes which extend in 3D from the center of the wiper pivot to the distant streetlight.

Seen in the "eye" of cat's-eye gemstones, where the effect is called Chatoyancy. I suppose we could call the entire scratch-hologram topic by the name "harnessed Chatoyancy."

Seen on spools of wire, fishline or transparent thread, as well as on brushed metal cylinders. The optical highlights seem to exist deep within the surface.

Seen on the back of large silicon IC wafers, where the diamond saw marks create holograms of glowing lines. The images seem to exist deep within the surface.

The scratch-hologram effect is responsible for the 3D luster or illusory "depth" seen in many thin surface finishes:

  • thin Mother-of-pearl, and mother-of-pearl paint
  • Polished 'burl' wood
  • 'pearlescent' metal-flake swirl paint
  • large stainless steel restaurant equipment in burger joints.
  • straight, slightly-wavy hair (those glowing 'deep' highlights)
  • Moire' silk
  • "deep highlights" of car bodies finished with electric buffers

3D effects are intentionally produced on steel surfaces through use of a wire-brush power tool. The larger the diameter of the brush, the deeper will be the apparent highlights.

Automobile tail-lights reflected on a wet highway create red streaks which seem to spear downwards into the black depths of the road.

At night, the distant lights on the shore of a slightly wind-rippled lake create shafts of light that seem to extend downwards to infinity.

Ridges of fresnel lenses create bright 3D stripes. Some overhead projectors create an illusory 3D bright spear of light which starts at the center of the lens and extends downwards.

The reflection of the setting or rising sun or moon on the ocean appears as a bright stripe which starts at the distant location of the sun, and extends vertically downwards into the water.

In store display windows, chrome window blinds with tracklights on the ceiling can create bright stripe reflections which sweep diagonally downwards in 3D. I remember this one well, because in the 1980s every time I noticed it, I wondered if it could be harnessed in order to create 3D photographs without holography. Years later I got my wish. "Prepared mind" and all that.

Smeared, greasy fingerprints on dark polished surfaces create small C-shaped highlights. These are abrasion-holograms of your finger pad. The complete hologram is destroyed as your finger moves across the plastic, leaving only a partial hologram of the trailing edge of the finger pad, hence the "C" shape.

Old, heavily-scratched plexiglas when held in the sun and tilted to various angles will show all kinds of patterns in depth. These are accidental abrasion holograms of the surface of whatever object created the scratches.

The "Pillars of light" weather phenomena caused by ice crystal plates, plates which fall with faces oriented parallel to the earth. Each light "pillar" seems to extend upwards in 3D from ground-based light sources (streetlights, etc.,) up to the zenith.

And of course, car-hood holograms of hands, buffing tools, gritty rag patterns, lambskin polishing mits, etc. Today this error in your car's finish is called "hologramming."


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