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Thank you, Martin, I have sent you an email.

[quote="Joe Farina"] I suspect that fringe integrity has a lot to do with it. The planes of micro-voids seem to be getting distorted during processing. With "normal" DCG this doesn't seem to as much of an issue.[/quote]

Obviously, there seems to be less crosslinking action taking place within a MBDCG layer.
I wonder if there's also a problem of getting rid of the TMG (which certainly acts like a plasticizer on the gelatin) during the post processing.
Would it make a difference if you removed the TMG with say, an alcohol (ethanol/ or sopropyl) bath prior to the water swelling step?

By the way, speaking of TMG, I lately read in a Lessard paper (?) about the option of using other amines for spectrally sensitzed DCG, providing similar speed levels like TMG.
One was dimethylamoethyl-methylaminoethanol and the other one was dimethylethanolamine.


[quote="Joe Farina"] One simply needs to wait for the layer to get hard enough due to the dark reaction. With Jeff's MBDCG, the plates don't seem to harden (at least in the short term ~2 weeks at room temperature, beyond which they may lose effectiveness for other reasons). As you pointed out, chromate is less reactive compared to dichromate, plus the concentration is very low, and the pH is quite high (9.0 to 9.5). I think a harder layer before exposure will help preserve fringe integrity.[/quote]

I assume that adding formaldehyde to the MBDCG solution won't be compatible???

Thank you Martin, that certainly helps.

If extra hardening is possible in narrowband DCG, then it may prove beneficial. When using thicker layers and soft gelatin, I've seen quite a few variations in the final image, with regards to size of viewing "aperture," color shifts with changing angles, and overall shrinkage. Some holograms are good, and some are not so good. I suspect that fringe integrity has a lot to do with it. The planes of micro-voids seem to be getting distorted during processing. With "normal" DCG this doesn't seem to as much of an issue. One simply needs to wait for the layer to get hard enough due to the dark reaction. With Jeff's MBDCG, the plates don't seem to harden (at least in the short term ~2 weeks at room temperature, beyond which they may lose effectiveness for other reasons). As you pointed out, chromate is less reactive compared to dichromate, plus the concentration is very low, and the pH is quite high (9.0 to 9.5). I think a harder layer before exposure will help preserve fringe integrity.

[quote="Joe Farina"]I was wondering if this need to swell is the same for narrowband as opposed to broadband DCG.[/quote]

A broadband regime definitely requires increased swelling in my opinion. In that case you'd want to introduce more "non-linearities" into the layer resulting in much greater variety of microvoid size. Perhaps this has also an impact on the location of the microvoids within the layer according to their size. I'd expect the larger ones to be closer to the surface. That's probably valid for SHSG, FEG, monomer sensitized gelatin, diazo gelatin and similar systems as well.

It seems that exposed DCG needs to swell to a certain degree in water, before dehydration in alcohol, to produce the right kind of air-voids (to make a good DCG hologram).

I was wondering if this need to swell is the same for narrowband as opposed to broadband DCG.

Narrowband DCG is associated with thicker layers and cooler processing temperatures, while broadband tends to suggest thinner layers and warmer processing (at least to me).

It would seem that harder gelatin could be better in narrowband processing (thicker layers, cooler processing). If anyone can shed light on this, I would appreciate it.