Mottled holograms

[jsfisher]

I'm having a problem. My post recent attempts to produce simple Denisyuk reflection holograms have yielded very poor results. It is as if you are looking through a scummy window when viewing the image. The image is well-formed, but partially obscured by a mottled cloud.

My setup is stable according to an interferometer. I suppose the exposure times could be off, but my simple solar-cell light meter disagrees. PFG-01 plates and JD-2 chemistry, if that matters.

[holorefugee]

Whenever I have had problems I would describe as mottled I look at processing. Is my squeegee good, am I stirring my chemistry...

[jsfisher]

Whenever I have had problems I would describe as mottled I look at processing. Is my squeegee good, am I stirring my chemistry...

I fall into the "doesn't squeegee at all" camp. I tried it a couple of times with PFG-03. I didn't realize how soft the gelatin was. What a disaster. My understanding was that squeegeeing was to speed drying and reduce water spots. I can believe bad squeegeeing could cause interesting image problems, but I wouldn't think not doing it at all would cause the problem I'm having, would it?

[Joe Farina]

I would agree with Holorefugee, "mottled" sounds like a processing or chemistry problem. It might help if a photo is posted, some of the people with experience with PFG-01 might be able to help. I've only used PFG-03, and I know how soft the emulsion is, and how sensitive it is to warm water. I seem to recall that PFG-01 is considerably harder, so maybe a squeege is OK? It might also help to look at the Slavich website, and see what they have to say, if you haven't done that already.

[Viking]

I use PFG-01. I always squeegee. And not very carefully / softly. Nothing bad ever happened.

[Hugo_C]

I have use PFG-01 and always squeegee, the emulsion in this harder enought, I wouldn't recomend that with PFG-03, thtats kinda soft emulsion, I picture will help a lot, but sounds more like a chemistry issue.

[jsfisher]

The attached photos are of a hologram i made of color push pins in a plastic cup. As with most attempts at photographing holograms, the actual is much better than the pictures. Still, though, I think you can see that it is looking through a scummed up window at the pins.

[jsfisher]

I retried shooting the push pins, but used the bleach from the JD-4 chemistry in place of the JD-2 bleach. The result was a little bit of blue fogging on the plate, and still something of a mottled, scummy view through the plate, but the image itself is much brighter than the JD-2 bleach version. It makes the "dirty window" much less noticeable.

[Joe Farina]

Well, you're getting images, so that's a good thing. I assume that if you put a white card in front of the plate, and shine your expanded laser on that, it's a reasonably clean beam (you're not seeing swirls and patterns in the expanded beam). If the beam is clean, and you're certain that the mottling is on the emulsion (i.e. the "surface" of the hologram), then there must be something happening with the processing (the chemistry or technique).

I have a couple suggestions when starting out with silver halide plates. First, choose a good object that is white or silver, and make sure it's stable. Metal or ceramic objects are good. Plastic is not so good. Second, make sure your plate doesn't wobble. Use a good, solid plateholder, or some other means to keep the plate very stable in relation to the object. If you are resting the plate directly on top of the plastic cup, that's not good at all. Finally, after you get the mottling problem worked out, split the beam and use one beam for reference, and the other for side-lighting of the object. You don't need an expensive variable beamsplitter, just a 70/30, 50/50, or something like that. The brightness of the holograms will increase dramatically.