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After a pause of maybe 5 years I am again attempting to shoot on Ilford plates, which were decades old 5 years ago. When last shot they gave
decent images, now the images are very faint. Their storage keeping conditions have not changed over time, and run from 60-70F. Processing is D-19, ferric EDTA bleach. I have not yet gotten to ascorbic redevelopment. The best image so far was at an OD of about 1.0 just after development. Darker OD so far is worse.

Any ideas??

If you make transmission holograms, OD 1.0 sounds reasonable.

Humidity?

I am making Denisyuk reflection holos.

The humidity is not measured but stays stable and relatively low, as the storage is in the basement and the
lab is there too.

Just a thought here... I would thing as the plate ages it loses its speck of silver over time, I think if you use a ascorbic , or weak developer to bring back life to the plate, before exposing it...just a thought

If the image is dim, then either you're not getting the same modulation you were getting, or the developer isn't penetrating into the emulsion.

In the first case, low modulation, it would seem that the sensitivity has gone down. This would imply that the some of the silver grains are no longer capturing photons, because they are no longer silver halide? Some kind of oxidation process? Perhaps Martin will know.

In the second case, developer not penetrating, it could be that the gelatin itself has hardened, perhaps reticulated. It's possible that in a 70 deg environment, over several years, the gelatin itself has cross linked, thus hardening it.

I think the best way to test, 1st test to see if it's a lost in sensitive by hyper bath of tea, and a 2nd test to see if gel is too hard by bath of uric acid, to soften gel...just a idea

I'd put bath the plates:
- in a dilute EDTA bleaching solution,
- re-activate in a 1% ascorbic acid solution (pH 6). Alternatively, you might use TEA.

Dear All,

As far as development penetration, the plates appear to darken in developer under the safelight at a normal rate, so penetration may not be the issue. However, that can be further tested....There is no visible reticulation before or after exposure.....Thank you for these suggestions. They seem entirely practical.

The darkness of the film may be due to the first few layers on the surface of the film. That is, it may be darkening because of development of, maybe, a micron or two in an eight micron emulsion.