Exposure time was 5 minutes with a TEC controlled laser diode.
I have made some new discoveries and some small adjustments in the formula that I will post on the Wiki tonight or tomorrow.
Little MBDCG Holo
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Hans
Little MBDCG Holo
Here is a sample of a MBDCG that I just made with my adjustments to the original MBDCG. Due to temperature/moisture in my garage, I would never have been able to do this in my garage with classical MBDCG as was invented by Jeff Blyth because of fading (crystallizing) of the MB in the plate.
Exposure time was 5 minutes with a TEC controlled laser diode.
I have made some new discoveries and some small adjustments in the formula that I will post on the Wiki tonight or tomorrow.
Exposure time was 5 minutes with a TEC controlled laser diode.
I have made some new discoveries and some small adjustments in the formula that I will post on the Wiki tonight or tomorrow.
Last edited by Hans on Wed Jun 13, 2007 4:36 pm, edited 1 time in total.
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Hans
Little MBDCG Holo
And here is another hologram. Also 5 minutes exposure, but with a hardening post exposure of 42 seconds (according to the post-exposure 1:7 rule I described in the Wiki). I believe that the post exposure has the same effect as a hardener in the fix for a normal DCG hologram.
This hologram is much brighter than the previous one. It is so bright that I could not make any good photo of it. Both holograms appear milky in the photo's, but they are not. Both are pre-swollen to the point at which maximum brightness was achieved.
Another advantage about the post exposure method is that the holograms are much easier to develop. The colour variations that sometimes appear, contrasting area's with a lot and a little exposure energy, smoothen out and don't appear when using this method.
I wonder if the post-exposure method would enable a normal DCG to be developed in SM only (without a hardener).
This hologram is much brighter than the previous one. It is so bright that I could not make any good photo of it. Both holograms appear milky in the photo's, but they are not. Both are pre-swollen to the point at which maximum brightness was achieved.
Another advantage about the post exposure method is that the holograms are much easier to develop. The colour variations that sometimes appear, contrasting area's with a lot and a little exposure energy, smoothen out and don't appear when using this method.
I wonder if the post-exposure method would enable a normal DCG to be developed in SM only (without a hardener).
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JohnFP
Little MBDCG Holo
WOW!!! Great hologram Hans!!!
Yes, a post hardening with light or heat can replace a chemical hardener in the standard DCG process.
What is a little puzzling is the the light hardened hologram seems to be more broadband when I would think the more hardening the more narrow band.
May I ask, how did you process the first hologram (hardening wise)? Did you use fixer with hardener? Then how did you process the light hardened hologram, that is, did you light harden it and then process it the same (with fixer with hardener) or did you elliminate the chemical hardening?
Yes, a post hardening with light or heat can replace a chemical hardener in the standard DCG process.
What is a little puzzling is the the light hardened hologram seems to be more broadband when I would think the more hardening the more narrow band.
May I ask, how did you process the first hologram (hardening wise)? Did you use fixer with hardener? Then how did you process the light hardened hologram, that is, did you light harden it and then process it the same (with fixer with hardener) or did you elliminate the chemical hardening?
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Hans
Little MBDCG Holo
Both holograms were processed equally.
- First a long wash (10 minutes) in cold water to wash out the chemicals.
- A swelling bath at 26C. I found that for thick coatings, this bath needs to be at least one minute. Otherwise dim area's will appear on the hologram.
- 35% IPA at 25C, two minutes
- 70% IPA at 25C, two minutes
- 99% IPA at 25C, three minutes
I use no fixer.
Remember that in classic DCG, the fixer is needed to convert the Cr(V) to Cr(III). It is the Cr(III) that hardens the fringes in the gelatin. With MBDCG it is the Methylene Blue that does that job. Cr(VI) is converted directly to Cr(III) upon illumination, and thus elliminating the need for a fixer.
In previous experiments I found a great benifit in using a hardener before the swelling baths. But because my hardener was getting old so fast, I started to experiment with post exposures. I found the effect to be similar. I prefer the post exposure method over a hardening bath because it cancels out two big variables: Temperature of the hardening bath and age of the hardening chemicals.
With a post exposure there is only one variable: Post exposure time. Experimentally, a post exposure time of 1/7 of the normal exposure time seems to work fine. I just wiggle the plate in the expanded laser beam at about the same distance where the plate was when the hologram was exposed.
I have not found a little difference in bandwith between post exposed plates and chemically hardened plates. Post exposed plates indeed are a little bit more broadband. But that to me is a benifit.
- First a long wash (10 minutes) in cold water to wash out the chemicals.
- A swelling bath at 26C. I found that for thick coatings, this bath needs to be at least one minute. Otherwise dim area's will appear on the hologram.
- 35% IPA at 25C, two minutes
- 70% IPA at 25C, two minutes
- 99% IPA at 25C, three minutes
I use no fixer.
Remember that in classic DCG, the fixer is needed to convert the Cr(V) to Cr(III). It is the Cr(III) that hardens the fringes in the gelatin. With MBDCG it is the Methylene Blue that does that job. Cr(VI) is converted directly to Cr(III) upon illumination, and thus elliminating the need for a fixer.
In previous experiments I found a great benifit in using a hardener before the swelling baths. But because my hardener was getting old so fast, I started to experiment with post exposures. I found the effect to be similar. I prefer the post exposure method over a hardening bath because it cancels out two big variables: Temperature of the hardening bath and age of the hardening chemicals.
With a post exposure there is only one variable: Post exposure time. Experimentally, a post exposure time of 1/7 of the normal exposure time seems to work fine. I just wiggle the plate in the expanded laser beam at about the same distance where the plate was when the hologram was exposed.
I have not found a little difference in bandwith between post exposed plates and chemically hardened plates. Post exposed plates indeed are a little bit more broadband. But that to me is a benifit.
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JohnFP
Little MBDCG Holo
Thanks Hans!
It sounds like you have experimented with the hardening times. What happens if you harden longer? Say 1/2 the exposure time or even the same as exposure time?
It sounds like you have experimented with the hardening times. What happens if you harden longer? Say 1/2 the exposure time or even the same as exposure time?
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Hans
Little MBDCG Holo
I have never post exposed that long. I experimentally increased the post exposure time until I had no random colour changes in the final hologram. I found the following effects without post hardening/exposure:
- With varying film thicknesses, colour changes occur in the final hologram.
- With varying exposure intensities/beam ratio's, colour changes occur.
- The only way to minimize those colour changes was to increase the swelling temperature and make the hologram broadband (higher pre-swell temperature).
- But with making the hologram broadband, the area's that received less exposure , such as the edges of the plate, those area's often became noisy and milky before the area's with sufficient exposure became broad band. I found that there was a very narrow pre-swell temperature range where it was sometimes possible to make very contasty subjects appear in a smooth colour in the hologram. If you even go .5C over this temperature range and BOOM, the hologram becomes milky and noisy.
- So, after I found out that a hardening fix resolved this problem, I started experimenting with varying post exposure times (without chemical hardening).
- I increased the post exposure times between test plates until I got a good result. That is how I found the 1:7 rule. However, this value might differ between techniques and chemicals.
- With varying film thicknesses, colour changes occur in the final hologram.
- With varying exposure intensities/beam ratio's, colour changes occur.
- The only way to minimize those colour changes was to increase the swelling temperature and make the hologram broadband (higher pre-swell temperature).
- But with making the hologram broadband, the area's that received less exposure , such as the edges of the plate, those area's often became noisy and milky before the area's with sufficient exposure became broad band. I found that there was a very narrow pre-swell temperature range where it was sometimes possible to make very contasty subjects appear in a smooth colour in the hologram. If you even go .5C over this temperature range and BOOM, the hologram becomes milky and noisy.
- So, after I found out that a hardening fix resolved this problem, I started experimenting with varying post exposure times (without chemical hardening).
- I increased the post exposure times between test plates until I got a good result. That is how I found the 1:7 rule. However, this value might differ between techniques and chemicals.