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After some more tests this morning, I think the reason for the slightly yellower appearance of the one sample (non-de-aired) is simply because it's volume looks darker, due to the presence of more air/bubbles scattering more light. This would seem to be confirmed by the apparent increase in total in...

Not clearly visible in the photo, but the beam going through the lower (non-de-aired) sample had a blue-green appearance, unlike the upper de-aired sample, where the beam appeared more colorless. P1010071.JPG Edit: After more tests later this day, this effect should be probably ignored, because I fo...

Thanks Din for your helpful comments. Today I did another test of de-aired vs. non-de-aired gelatin. This is 280 bloom Gelita photographic gelatin (6 grams gelatin + 47ml water). One test was de-aired at 26 inches mercury, the other one was agitated w/magnetic stirring to introduce bubbles (although...

Just a note about gelatin gelling and drying. After a few days in the fridge, the gelatin (no dichromate) dried, and became like a hard plastic, almost like acrylic. Didn't realize how hard it gets. Also, it shrinks enormously, compared to the gel state. The photo below shows the same gelled cubes I...

From prior discussions on the forum, I've gathered that increasing exposure is not the best way to produce better DCG holograms. Besides increased risk of object movement, laser instability, etc., there are other factors. One thing which Din had pointed out was that DCG does not have an exposure thr...

Thanks Martin. I've printed a copy of that paper, and will be taking a closer look. Once, I did a test using a hot-dried DCG plate. The gelatin never got the chance to gel (which was intentional). It produced a weak hologram, so I didn't pursue it further. I have an old paper which talks about hot-d...

Thank you, Din, I'm grateful for your help. The method you illustrated would be a precise way of determining scattering, I will keep it in mind. Since the silicone molds produce cubes of the same size, I was also thinking of measuring the simple transmittance of different cubes of gelatin. I'll have...

Did two tests regarding noise (scattering) in gelatin. The first one was to compare possible noise due to lower-temperature heating of the mixed emulsion (40C for 30 minutes) as opposed to 50C for 2 hours. I used silicone cube molds (for making candy, available on Amazon). The gelatin was pure, with...

The first thing that occurred to me was the size of the reproduction source. But, you say you can get sharp holograms with silver, so this does not appear to be the problem. Joy asked if you used the same source, at the same distance, for the sharp hologram as the blurred ones. I forgot to reply to...