First DCG, Please, Help me find the problem.

This is a forum to share experiences and ideas about holography.
Kiffdino

First DCG, Please, Help me find the problem.

Post by Kiffdino » Sun Mar 08, 2009 7:02 pm

hi Dutchelm05,
i dont think it was oversatuaration cause i didnt change anything in the process
and last time it worked
still 5% potassium dichromate solution, sensitizing for 30 sec
but temperature might have been an issue.
i did the sensetizing on my balkony in the dark at about 5°C "roomtemperature!" :lol:
and i wanted to incorporate Dave's advice to put the plates on a sponge for 20 minutes and leftg them in the cold. before moving them inside the drying box. It might have been another mistake to put the dryingbox next to a heater for another hour. Maybe the temperature switch was too fast.
And again the soap might have had a bad formulation.

But anyway, next time i mix the dichromate in the gelatin from the beginning on.
I'll give you an update as soon as i get it done. Don't worry ill hang in there...

Kiffdino

First DCG, Please, Help me find the problem.

Post by Kiffdino » Sat Sep 04, 2010 12:08 pm

Hey guys, been some time, here is an update.
I paused with DCG for a while cause I was looking for a new location for my lab.
Now I've set up a new one in an old bunker.

Past two weeks I made a few tests and thanks to Dave answering many questions over skype, things are starting to improve.
Anyway I'm still not content with the outcome.

The hologram is made with the c315 m at max output ( i dont know if thats 100mw).

I veil coated the plates 3:12:100. So after 12grams of gelatine dissolved in 100 ml of water I added 3 grams of potassium dichromate.
Plates were dried for 4 hours and then put in the fridge.
This plate has been 1 day in the fridge in an airtight box.
When I took it out, I blow dried the emulsion side for about 30 seconds to stop condesation.

Exposure 1min
Dark reaction 5 min
Light fix under 50watt halogen light at about 1 meter distance 2.5 min
Fixer "Tetenal" 30 sec (I've got the kodak rapid fixer aswell, but everytime I use it I get bad results)
1 water bath 60 seconds
2 water bath 60 seconds
ISO 70% 30 seconds
ISO 90% 30 seconds
ISO 100% at about 35°C for 45 seconds
Blowdrying 5 min
Oven at 100°C for 10 min

Video: http://www.youtube.com/watch?v=qmqk8hu34yI

Why ist the holgram white? I wanted a green crocodile eye :D .
This was the first time i coated the glass plates with gelatin and dichromate directly.
All the times before I first coated with gelatin, then put it in the fridge and when I needed them i sensetized them with 5g of dichromate in 200ml of water.
The plates from those tests seemed to be more sensetive and brighter, but i also had massive cristilization problems.

One more thing. The holograms I made are not really sharp. I have made the same hologram (croc eye) on a silver plate, and you could see way more detail in it.

Please help me to get better results, should i increase the dichromate in the gelatine ?
Dave recommended kicker mirrors, it did that on a few shots, but i only got massive internal reflections in the holograms.
Attachments
eye.jpg
eye.jpg (111.85 KiB) Viewed 2659 times
setup.jpg
setup.jpg (174.35 KiB) Viewed 2659 times

Joe Farina

First DCG, Please, Help me find the problem.

Post by Joe Farina » Sat Sep 04, 2010 1:24 pm

Hello Kiffdino. Dave would be the person to ask about the percentage of dichromate for DCG when exposing with a 315M, I've never done it.

With plates stored in the fridge, I've gotten better results when the plates had aged for a while. But I was using different exposure/processing than you. Four hours drying is good, preferably under a gentle air flow (a fan). Airtight box and blow-drying to prevent condensation are good. Exposure -- ask Dave. It would help to know what the actual output of your laser is. Dark reaction 5 minutes is good. I see you're using both the light builb and fixer for the "development" step. Is there a reason for that? With the light bulb, I did not use a halogen light at 1 meter. I used an ordinary frosted 100W light bulb at 6 inches. I doubt that 50W halogen at 1 meter is doing much. I would try everything without the Tetenal (or Kodak) fixer and try to get things to work. If not then go back to using fixer, if that seems to help.

I strongly discourage using hot IPA. I really don't think it's necessary. But I would vary the temperature of the first water bath, this will determine the amount of swelling. Why are you using two water baths? I would have all the liquids at room temperature, and raise the temp of the water soak only as needed.

The photo looks like a broadband milky result, which I associate with soft gelatin or warmer soaking water. If the plate has only been in the fridge for a day, then it might be quite soft. You might want to give those younger plates more exposure to the 100W light bulb at 6 inches. Everything else looks OK. One last thing, there's no substitute for making lots of exposures and tests. I would make a batch of about 20 plates at a time. Be prepared for lots of rejects after processing. I could judge my own progress by looking at my "rejects" box of DCG plates, which gradually showed more and more diffraction.

Joe Farina

First DCG, Please, Help me find the problem.

Post by Joe Farina » Sat Sep 04, 2010 1:51 pm

After looking at your description and photo some more, maybe your plate is underexposed. I would definitely ask Dave about the dichromate and exposure time. I think 1 minute may be too short of an exposure, from what I remember. 3 grams of dichromate may be too little for 532nm. Hopefully Dave will chime in here. When Rallison defines the result from an underexposed/underdeveloped plate he calls it "bad fog, dim, weak."

Thieu

First DCG, Please, Help me find the problem.

Post by Thieu » Sat Sep 04, 2010 3:50 pm

Hi Kiffdino, I'm a beginner as well with DCG, but I've been going along the same path. I'd definitely say underexposed and underhardened. When there's milkiness, you can decrease the temperature of your developing bath, but somehow the effect is not the same as exposing and hardening more and developing at a higher temperature. What gelatin do you use? I used dr Oetker, it must be available in Germany as well, maybe it's the one you used. It's quite a soft gelatin and needs quite a bit of hardening. For the hologram that I posted to the gallery, these were my exact parameters:

-age of plate, 3 days before being sensitized with dip 'n shoot.
- exposure 5 minutes with about 20-30 mW of 445nm spread out to a 15x100cm beam. You probably need a lot more at 532. You have to try how much.
- hardening with 70W philips eco classic lamp at 20 cm distance for 2 minutes.
- dark reaction 5 minutes
- rinse in a bucket of room temp water to get the dichro out.
- develop at 32 C for 1minute.
- flood it quickly and completely with room temp 100% ipa. So no gentle increase of ipa conc, more like an ipa shock.
- dry close up with blow dryer.

I'd say try to harden the same way and amount of time and increase your exposure time in steps.

I'm just a beginner compared to the people here, so I'm in no way claiming this is the "right" way to do it. And my exposure time is very long, considering it's 445nm. I hope with Joe's gelatin this will improve. But the hologram I made is about the same brightness as the object itself in the same light, so I must be doing something right :-)

Joe Farina

First DCG, Please, Help me find the problem.

Post by Joe Farina » Sat Sep 04, 2010 6:27 pm

Thieu wrote:- dark reaction 5 minutes
- rinse in a bucket of room temp water to get the dichro out.
- develop at 32 C for 1minute.
Hi Thieu, after reading this, I was wondering if you tried reversing Steps 2 and 3. In other words, develop with light bulb or fixer, then rinse in the bucket afterwards (assuming you're using the light bulb, if you're using fixer, the dichro would wash out in that). I think rinsing prior to "developing" is contrary to normal practice. Not that there's anything wrong with being contrary :wink: , but I would try reversing those steps if you haven't done it already.

Kiffdino, the following quote from Rallison may help:

"Developing is simply a process of reducing the reamining chromate ions and thereby uniformly hardening the gelatin. Too much hardening will give a clean, clear but weak and green result. Too little hardening will leave the hologram milky and weak and reddish or yellowish. Development is done either optically or chemically using fluorescent or incandescent lamps or any suitable reducing agent or tanning solution."

Thieu

First DCG, Please, Help me find the problem.

Post by Thieu » Sat Sep 04, 2010 7:25 pm

Hi Joe,

The reason I do it this way is mainly because of the environment. I do the "developing" (we should find a better word for that) in a tray in the sink, and I mix some hot and cold tap water until the temperature is right. I have to drain this water, cause after the "developing" it's cold again. So I rather not have any dichromate in it. That's why I use the bucket first. It can be reused many times, and reduced with metabisulphite and discarded if it becomes too yellow. And there's virtually no dichromate in subsequent baths. It was not my idea to do it this way, I found it somewhere in the literature, not sure where. It makes sense that it works though, because if "developing" at 32 C then rinsing at 20 doesn't do much to the gelatin, but it does get the dichromate out. I never use chemical fixer. To be honest, I never really bothered to check if it's available here. I'll see if I can find the article where I read it. And maybe if, to quote Rallison: "the rest is a snap" one day, I'll do the reverse to check out if it *really* doesn't make a difference. :-)

Thieu

First DCG, Please, Help me find the problem.

Post by Thieu » Sat Sep 04, 2010 7:45 pm

Hi Joe, after reading your post again, I realized that the term "developing" is the cause of the confusion here. I use it to describe the step where you put the plate in a bath of precise temperature, to wash the gelatin out that's not hardened enough to resist dissolving at that temperature. I would call that developing because it mostly resembles the equivalent in silver chemistry, a latent image (invisible differences in hardness) is transformed into a real one, be it through a completely different mechanism. But it looks like what many other ppl call developing is really the chemical hardening. Indeed it doesn't make any sense to do that after the rinsing, cause with the light bulb there's not much to harden with if the dichro is out. :-)

To sum it up, I do: expose, light bulb, dark reaction, rinse, "the magical step in a controlled temperature bath that I promise to never call developing again", IPA, dry. :-)

Kiffdino

First DCG, Please, Help me find the problem.

Post by Kiffdino » Sun Sep 05, 2010 6:57 am

Hi.
Thankyou for the response.
Well the gelatin is from Gelatia, 220 bloom. It says ultra high quality or something on the box.
That stuff must be good. :wink:
Okay, well i used 2 water baths cause thats what I read in the Holo Wiki.

I might have made a mistake there because I exposed for 1 minute, then I did the dark reaction for 5 minutes and AFTER that I did the light fixing.

If I read your posts correctly you do the fixing instantly after the exposure and then keep it for 5 minutes in the dark.
I will try that.

I will also do tests without the chemical fixer.

Thieu

First DCG, Please, Help me find the problem.

Post by Thieu » Sun Sep 05, 2010 9:59 am

Kiffdino wrote:Hi.
If I read your posts correctly you do the fixing instantly after the exposure and then keep it for 5 minutes in the dark.
That's correct. It allows the exposure from the fixing to reach its full effect.

By the way, you didn't mention the temperatures of your two water baths, the ones after the fixer and before the first ipa. The exact temperature of those is very important. A couple of degrees higher or lower can mean the difference between milky and good. My first holograms looked very much like yours, and the transition point was around 25 degrees. Now that I lamp fix more, it's risen to 32 degrees. The temperature of the transition point is a good measure of how hard your gelatin has become by the baseline fixing exposure and/or chemical fixer and its intrinsic hardness. A couple of times I tried the G307 process with a very long exposure and baking step, and the transition temperature had risen to >80 degrees :-). It was impossible to get the gelatin off the plates using tap water...

I also found that you can reprocess quite a lot of times, increasing the temperature of you water baths a degree at a time. It allows you to find the transition point of a plate quite nicely. However, when you go over the point and it turns milky there's no way back. But a new exposure with the same parameters will be fine with one "water step" at the last temperature you tried or slightly below. So there doesn't seem to be a cumulative effect.

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