Hello everybody!
Finally I had some more time and patience and made some new mold coated plates, using
culinary gelatin, and AmDi. using and aproximate ratio of 100:13:4, the water used was tap water! =)
The emulsion was mold coated without any spacers so I guess it got very very thin, the plates
are light yellow. I had a thicker plate that partially melted after I separated it from the mold and left it to dry...
Usually I have to make quite long exposures to get nice images with my coherent 215 30mw.
For my surprise this time when I exposed 5 minutes I got a very very blue/purple image,
I did several shots, this time reducing exposure time as low as 30 seconds so I could get a result shifted as
much as possible to the red, the resulting holograms were still blueish, but more broadband, having also a brownish
hue mixed with the blue, which was very nice.
Developing was done using a metabissulfite and alum bath for washing, then a water bath, and then 50% cold IPA, and 100% hot bath followed by hot air blow drying.
The plates are only 1 day old so they get a bit milky still.
I wonder why they are so sensitive? Could it be the very small thickness of the emulsion?
Unfortunatelly the resulting holograms never get too bright, and they are very sensitive to moisture, so I have to seal them imediatelly,
if I reprocess them they get so blueshifted that they get really dim and purple...
What could I do to be able to process them in a way that I can get at least some tiny redshift?
What do you think will happen when plates age a bit? I hope they don't get hopelessly blue as I made so many of them...
I'll post some pictures tommorrow if I can...
Best regards
Filipe Alves
Very sensitive DCG
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Joe Farina
- Posts: 805
- Joined: Wed Jan 07, 2015 2:10 pm
Very sensitive DCG
The fact that you were able to get a hologram with a 30 second exposure with 30mW at 532nm is interesting. What gelatin are you using? Or maybe there's something in your tap water 
If your existing film formula can make a hologram with only 30 seconds, the first thing I would do is decrease the dichromate concentration (and increase the exposure time to compensate) to get a red shift. If your emulsion contains a lower percentage of dichromate, there's less material to wash out of the layer, and it will shrink less.
If your existing film formula can make a hologram with only 30 seconds, the first thing I would do is decrease the dichromate concentration (and increase the exposure time to compensate) to get a red shift. If your emulsion contains a lower percentage of dichromate, there's less material to wash out of the layer, and it will shrink less.
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Tony
Very sensitive DCG
Heat and humidity will do two things.
Increase the exposure sensitivity (sometimes by a lot) and cause ut to go blue.
Can you tell us in what manner the film was stored?
The AmDi ratio looks about right for green IMO.
I would also be wary of your metabissulfite and alum bath. I am not sure how well that is controled. Has the ratio of these two chemicals changed?
Best of luck
T
Increase the exposure sensitivity (sometimes by a lot) and cause ut to go blue.
Can you tell us in what manner the film was stored?
The AmDi ratio looks about right for green IMO.
I would also be wary of your metabissulfite and alum bath. I am not sure how well that is controled. Has the ratio of these two chemicals changed?
Best of luck
T
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manalokos
Very sensitive DCG
Hello Tony, Joe,
Tony, my house is a bit humid right now as it has been rainy for two weeks now...
I store my plates in a closed box with one of those desiccant containers that have some
kind of crystals that turn into a liquid on the bottom... The "fixing" bath I use mostly to get rid of the yellow
as I don't notice any great difference between that and an plain tap water bath... so I have an arbitrary
ration of meta and alum in it...
The ratio looks nice, but maybe things may get strange when the emulsion is too thin, I notice
that the dynamic range of the plates is quite less, if the beam is narrower I can see very underexposed edges,
a nice brownish rim and a blue or purple and very dim center, usually the plates are more tolerant
to exposure time... could be the emulsion too thin?? Is there a limit for the thickness of the emulsion?
Joe, I use some culinary gelatin I bought in the supermarket for 50 cents a package! =)
30 seconds is enough to see an hologram but it is underexposed...
Maybe there is really something in my tap water, which is great, I can start a business selling "holographic water"!!
Best regards
Filipe
Tony, my house is a bit humid right now as it has been rainy for two weeks now...
I store my plates in a closed box with one of those desiccant containers that have some
kind of crystals that turn into a liquid on the bottom... The "fixing" bath I use mostly to get rid of the yellow
as I don't notice any great difference between that and an plain tap water bath... so I have an arbitrary
ration of meta and alum in it...
The ratio looks nice, but maybe things may get strange when the emulsion is too thin, I notice
that the dynamic range of the plates is quite less, if the beam is narrower I can see very underexposed edges,
a nice brownish rim and a blue or purple and very dim center, usually the plates are more tolerant
to exposure time... could be the emulsion too thin?? Is there a limit for the thickness of the emulsion?
Joe, I use some culinary gelatin I bought in the supermarket for 50 cents a package! =)
30 seconds is enough to see an hologram but it is underexposed...
Maybe there is really something in my tap water, which is great, I can start a business selling "holographic water"!!
Best regards
Filipe