Making the Exposure
Making the Exposure
The exact exposure time varies with the intensity of the laser light and the sensitivity of the film. You can use the following times as a start.
1 milliwatt laser 10 seconds
1.5 milliwatt laser 5 seconds
2 milliwatt laser 3 seconds
To make the exposure lift the shutter card off the isolation table, but keep it a position that still blocks the laser beam. Hold the card in this position for 15-30 seconds to let any vibration caused by lifting the card off the table to die down. Then lift the card completely, allowing the laser to expose the plate. After the exposure time has elapsed place the card back down blocking the laser beam. The plate is ready to be developed.
Developing Your Hologram
Developing holograms is simple. The chemistry used is no more dangerous than standard photo-chemistry. This means that the chemicals are toxic and can be absorbed through the skin. Even though I use tongs to move the holographic film from tray to tray I always wear rubber (playtex) gloves. You should too! You need three plastic trays large enough to hold a film. The trays are arranged as in figure 11. The first tray holds the developer, second tray water and the third tray contains the bleach.
The developer kit (see parts list) contains 8 fluid ounces of developer and 8 fluid ounces of bleach. The chemicals arereusable. The chemistry has a shelf life of 3-6 months in a closed bottle, and about 8 hours in an open tray. It's a good idea to re-bottle the chemistry as soon as you're finished developing your holograms. If you need to keep the chemistry in the trays for extended periods of time, you may cover the trays with a sheet of plastic or glass to slow down the oxidation.
Use a safelight for illumination during development.
The film is placed in the developer for two minutes; every 20-40 seconds gently rock the tray or move the film back and forth to keep fresh solution in contact with the film. The film will gather density and may appear to turn completely black. Don't worry, that's normal. Ideally the plate should appear about 80% dark by eye.
Remove the film from the developer and place it in the water tray for 15-30 seconds. This step isn't mandatory, but it extends the life of the bleach solution for subsequent reuse.
After the water, place the film in the bleach tray. Again rock the tray gently every 20-40 seconds as before. Keep the film in the bleach until it becomes completely transparent, this usually takes about one minute. When the film clears it is light safe. You can turn on standard room lighting now to finish development.
Remove the film from the bleach and put it back into the water tray. Bring the tray to a sink, run the cold water tap and place the tray under the running water for five minutes. Afterward, remove the film, stand it vertically against a wall and allow it to dry. The holographic image will not become visible until the hologram is completely dry.
The plate sometimes dry with water spots on them. You can dip the plate in Kodak Photo-flo solution (mix according to direction) after the final rinse to prevent water spots.
Some holographers wipe the film with a squeegee to remove excess water and thereby speed up drying. Others use a hair dryer to shorten the drying time. If you use a hair dryer, set it on warm or low, or you may damage the hologram from excessive heat.