Q: How do you make holograms that are visible in white light?
A: There are a lot of different types of holograms, including multiplex holograms- the kind that move, embossed holograms like on your credit card, and the "dichromate " holograms that I have produced. These were made with a delicate gelatin emulsion that must be hand-coated onto glass plates, then used immediately. The object to be reproduced had to be capable of absolute stillness-not wavering more than half an angstrom- for the (considerable) length of the exposure. I made my models with rocks, minerals, shells, and other things that struck me as doing interesting things when hit by light- things that didn't involve pigment color, that is, as the process is monochromatic. This doesn't mean that the holograms came out in black and white, rather that the colors they display are the result of other factors than reflected color.
The idea is to split a beam of laserlight into two- the "reference" beam, which is bounced around, diffused, and shined on the glass plate without hitting the model; and the "object" beam which illuminate the model, sending rays bouncing off it that intersect at the plate with the other part of the same beam coming in directly from the source. The interference pattern caused by these intersections is recorded by the photographic emulsion .When developed and illuminated with white light coming from the same direction as the reference beam, the interference is recreated and the model is reconstructed in space.
In a single hologram it is possible to capture two or even more three-dimensional scenes, by substituting a different model in front of the plate, while changing the angle of the reference beam. The visible scene then shifts from one model to the other as one changes one's angle of view. These are called "double channel" holograms or "flippers" (after the first commercial one, a "coin" that switched from heads to tails without turning over.) A lot of what I like about these holograms is the way one thing turns into another- a new way to juxtapose two different forms.
The emulsion on my holograms was covered with clear UV-set adhesive and a cover glass was applied, then the edges were sealed with epoxy. I have made 13/4 inch disks, 4"x5 "plates, and 8"x 10" plates. I offer them in frames, or I can set them in silver or gold jewelry, and I have lately been using them in my cast paint relief sculpture and wearable art. They are best illuminated by direct sunlight, but any undiffused light source, even a soft-white bulb, will work if enough distance is allowed between the hologram and the light. Of course, no photograph can adequately represent the way a hologram looks, so use your imagination when looking at the pictures in this page.
Andrew Werby - United Artworks
Stilbite/haliotis channel of a dichromate hologram by Andrew Werby 10 x 13 cm (4 x 5 inches) 1984
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