Lionel1972
Member
Great to know you're about to try it for real Holmburgers! Goodluck and let us see what you get.
Exposure: 2min @ f/8 bright sun
Processing:
9min soak in Glyaxol @ 65deg ( prev. was 6min, did not check end temp )
3min development @ 65deg ( actually I used drift 63deg start - 66deg end )
rinse 10min @ 66deg
30s soak in 2% glycerin + 3 drop LFN @ 66 deg ( 375ml total )
Hey Mssr. Shaffer, I forget now as it's been so long, but what are the possible substitutes for glyaxol. It's purpose is to harden the emulsion, right? Do you think chrome alum would do the trick?
Also, I forget the purpose of the glycerin and potential substitues. Not that it's a chore to get glycerin (http://www.walgreens.com/store/c/africare-100-glycerin-oil/ID=prod4118523-product) but I'm getting some Sorbitol for my screen plate stuff and I'm curious if that would work.
Long live Lippmann!
I would think that chrom alum would work, however you'll need to figure out what dilution and time to get sufficient hardening.
I believe that the idea of the glycerin is to re-swell the emulsion. I don't know what sorbitol is, so I can't help there.
Both of these steps are an attempt to keep the developed & dried emulsion the same thickness as the exposed emulsion. The shrinking emulsion will cause color shift or loss color image all together.
There may be better ways of post-swelling the emulsion. A while ago Jeff Blyth put some interesting posts on the now no longer existing holographyforum.org. Fortunately, two of them can be found here again: http://holoforum.org/forum/viewtopic.php?f=7&t=67&start=0
(Incidentally, all former holographyforum.org posts will soon become available on http://holoforum.org/ as well.)
The new swelling agents Jeff Blyth advocated for, are citric acid and succinic acid. They require a well hardened layer. Keep in mind that their efficiency may depend on the kind of hardening agents involved: aldehyde hardening seems to do better with these acids than say, chrome alum.
Hello
When I made Lippmann plates, I would add 2 ml of a 1% solution of chrome alum to about 100 ml of emulsion just before I was ready to make the plates. The glycerin was used in a 1-2 % solution to soak the plates in after processing. It would swell up the gelatin to bring the colors where they should be. If you left it too long the whole plate would go off,and the reflection would be godawful. But soaking it in distilled water and letting it dry would bring it back to what it was before. I started with 1% and maybe a 30sec dip
Glad to see someone else tilting at the windmill too. I spent about two years of making Lippmann plates before I got two that actually gave me something close to the actual colors in the scene. How are you developing your plates? Did you know you can produce holograms with these plates as well?
hope this helps
rob
But that is interesting about citric acid. How is it that citric acid will swell the emulsion?
to R Shaffer
Yes I liked gp-2 myself. Ascobate developers worked but the images faded out after 2-4 months. Also found that two isopropyl alcohol baths one at 70% and one at 90+% for two minutes each after developing really helped bring out the image.
The recipe I use came from Darran Green, who is really great about helping curious but clueless people like myself get a handle on this. I can PM it to you if you like.
There are modern papers written on Lippman photography, naturally I can't recall any now except the SPIE (society of photonics ,imaging and light) had a few. I would have to go and dig them up to see what I have
rob
Here's Jeff' Blyth's explanation (http://holoforum.org/forum/viewtopic.php?f=7&t=67&start=0):
However in the case of hologram treated with citric acid and then blow dried at room temperature we are left with a swollen gelatin which is different from the case of one swollen with water plus sorbitol or glycerol. In citric acid we have in effect the line of 3 carbons ins glycerol now with their alcohol groups (-OH) replaced by carboxylic acid groups (-COOH) except for the central carbon which has the (-COOH) added in place of H leaving one alcohol OH still there (mor on this later). These -COOH groups introduce a different effect to cause the swelling of the gelatin. This time the citric acid (-COOH) groups can partially displace the original internal (-COOH) groups from their attraction to the amino groups. Thse displaced (-COOH) groups are still firmly attached to the gelatin biopolymer of course and are not free to wander off in solution so the rest of the citric acid molecules is forced to be accomodated into the gelatin structureas most of the surrounding water is now evaporated off thus leaving the gelatin in a swollen state when it is left to equilibrate with ambient humidity.-- Fortunately it is a chemically weak arrangement easily completely reversed by plenty of fresh water so that it becomes energetically more favourable for all the ions involved to go back to surrounding themselves with water-molecule clouds again. The upshot of this is that if you are not satisified with the color of your treated hologram you can go back to square one without any difficulty.
One might add that the citric/succinic acid treatment is muss less aggressive to the emulsion than chemicals like urea for example.
The action of Urea is reversible, but it depends on hardness, hardening (type of hardener) and a number of other conditions.
Now, type of hardener is important as chrome and alum type hardeners can be undone but aldehyde hardeners generally cannot be undone. So, you see my point I hope. (it depends)
Sorry I cannot be more specific.
PE
I think citric and succinic acids were used with dichromated gelatin holograms, not silver halide.
The one time I tried citric acid with DCG it melted the coating right off the plate, so I never tried it again..
As for fixing lippmanns, I never did ,except for the backwards one I mentioned earlier . Just gp-2 , two alcohol baths and done. I haven't noticed any darkening in the older ones (2006).
In any event, citrates are not known as softening/swelling agents. The only one I can think of OTOMH is Urea, as I mentioned before. I might also add that there are reported cases of amino acids causing swelling or softening of gelatin.
I'm sure that Citric Acid acts as you say. I'm just saying that I am unaware of any use of it as a swelling agent.
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