Experimenting with delayed development

JohnK on the holography forum had asked if I’d experienced any problems with delayed development of VRP-M.  He’s been working on making holograms using a Coherent 315 and VRP-M film and was wondering VRP-M was sensitive to delays of several hours between exposure and development.

I normally develop right after exposure but did the following test to find out how VRP-M behaves.

I took a 2×3" piece of old VRP-M (made in Oct 2005) that had been treated in 6% TEA on Sep 8 and washed out and kept in a desiccant box at <20% humidity since and exposed it for 6 seconds for a calculated exposure of 83.7uJ.  Remember that this was with TEA treated film.

The first half of the film was developed in undiluted JD2 developer at 9:30pm on 9/11 and bleached in EDTA.  The developer wasn’t fresh, it was mixed on 9/11 at 6am but I keep my dev in a airtight container until it’s exhausted and the working developer was still a very light golden color.

The resulting hologram was reasonably bright but quite foggy which appears to be typical for this old batch of film.

The second half was put back into the desiccant box for 8 hours and finally developed and bleached the same as the first half.

I can’t see any difference between the two halves either in hologram quality or fogginess.

It looks like under these conditions VRP-M keeps pretty well at least for 8hrs.

There is one potentially major variable that I don’t have to face which John does.  Humidity.  I’m told by Integraf that VRP-M is sensitive to humidity and the humidity in the caves where John works is likely close to 100%.  There may be a fair amount of time needed for the film to swell and stabilize in that environment before a hologram can be made.  There may also be negative affects on the emulsion from the increased moisture content.

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Michael Harrison

Husband, Programmer, Irish dancer, tinkerer, astronomer, layabout (as much as possible)

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