A Simple DCG Recipe

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Here's my two cents:

From Joe Farina:

Mix dichromate, gelatin, and water using some kind of double-boiler method, and keep it under 60C. Coat plates using whatever method you prefer. Let them dry under a gentle air flow for 4 hours. Store your plates in the refrigerator (use lock & lock or some other kind of airtight container). Make as many plates as possible to enable lots of tests. Do not desiccate or do anything else to them. (By the way, use Knox gelatin from the grocery store.)

Now, do tests at your lesiure. Just take your container out of the fridge, let it get up to room temperature, and take a plate out (or you can immediately take it out if you hit the surface of the gelatin hard with warm air from a hairdryer to prevent excess condensation). Expose Denisyuk style with 100mW at 532. (I would say 2.5" X 2.5" plates would be good.) Let them set in the dark for 5 minutes after exposure. Rinse under cold tap water for a minute until the yellowness goes away. Soak in room-temperature water for a minute. Soak in 91% for a minute with agitation (room-temperature). Soak in 99% for three minutes with agitation (room-temperature). Then dry with hot air.

If there is milkiness, you will need to harden the gelatin more after the dark reaction. You can user fixer or a 100W light bulb 6 inches away (for varying time periods) to do this. I prefer the light bulb method.

See how your plates age, and how they perform over time. Change variables to see different results (well, I don't need to tell you this, since you probably know better than I do about trial-and-error work in holography). Just use the same principles you use to get such good silver halide holograms. One last word: don't try to pre-plan things too much. Just use the simplest DCG technique possible (it is really very simple if you have blue or green light). Don't make it any more complex than it has to be.

End of lecture.

  • With a C315M (532nm) at 100mw start with a 1 to 3 minute exposure and adjust by factors of two to find the right exposure range. ie. 45 seconds, 90 seconds, 180 seconds.