woelen
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Demo of old photographic process
The experiment I did today is something very different from the other experiments I did. It is a demonstration of the principle behind one of the old
photographic processes of 150 to 200 years ago. A lot can be improved, but the main principle easily is demonstrated with fairly benign chemicals.
http://woelen.homescience.net/science/chem/exps/cyanotype/in...
The ferric ammonium oxalate chemical can be replaced by ferric ammonium citrate. You can also make ferric ammonium oxalate easily by dissolving
freshly precipitated and rinsed Fe(OH)3 in just enough oxalic acid to which also some ammonia is added. No need to isolate the chemicals, just use a
solution, which is near neutral (faintly acidic is best, pH = 5 or something like that).
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a_bab
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That's an interesting application, and moreover it can also used to create holorams (with green light, and gelatin layer). It's not sensitive thought,
as it takes long exposures.
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unionised
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I knew you could use bichromated gelatin for holography but I didn't know that "blueprints" would work. Do you have a reference?
I played with this cyanoferrate reaction a while ago using a thin layer chromatography plate rather than paper. I also used a lens and I got an image
of the hous across the street. It wasn't very good but it proved that the technique worked.
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JohnWW
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How would that have compared with the Daguerrotype photographic process, invented by Daguerre in France in 1839? It involved the use of mercury vapor,
which would have been at least as hazardous as that cyanoferrate method.
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crazyboy
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I conducted a similar experiment but I painted the paper in silver chloride soln. then placed a piece of glass over it and put a paper "snow flake" on
top let it sit in the sun then rinse off the silver chloride.
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Sedit
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Woelen This is pretty cool.
Just out of curiosity what would result from the projection of a rainbow from a prism on the paper. Would it show a gradiant as the various
wavelenghts reacted or would you just get flat exposure?
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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UnintentionalChaos
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Quote: Originally posted by Sedit  | Woelen This is pretty cool.
Just out of curiosity what would result from the projection of a rainbow from a prism on the paper. Would it show a gradiant as the various
wavelenghts reacted or would you just get flat exposure? |
no, If you read the discussion section, you'd know that the reaction is triggered by short wavelength (which usually means hv, and possibly blue)
light. In this case, you would get flat exposure when you reached the proper wavelength and above.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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a_bab
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| Quote: Originally posted by unionised | I knew you could use bichromated gelatin for holography but I didn't know that "blueprints" would work. Do you have a reference?
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Here you go: http://spitbite.org/carbon/papers/TheChibaSystem.pdf
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unionised
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Thanks, but the link seems to be down.
Is this the sort of thing you mean?
http://www.holographyforum.org/phpBB2/viewtopic.php?f=2&...
It certainly looks interesting (and avoiding carcinogenic Cr(VI) compounds is a bonus)
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12AX7
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Cool!
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a_bab
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Yes, that's where I got the link and the info, too. If you need the doc, i got it, but as it's fairly big (5 megs) U2U me if you need it.
As about Cr+3 carcinogenity, I'd say it's overrated, but definately not something to drink. These holographer have been working with K2Cr3O7 since the
'70 for some, and yet they have not developed cancers of some sort. There are many things to discuss on this matter though.
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unionised
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I did some holography years ago. I was interested in the DCG because it gives good effects but I never really got round to anything because I never
had a blue /UV laser.
This would save me having to worry about Cr(VI) (and, BTW I have used it for other things since the 70s too) but I still need the laser.
Maybe I will look at blu ray players.
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a_bab
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Nowadays you can find easily with around 1500 bucks if you are lucky a good laser from the Coherent series. Just read the mentioned forum. With a
coherence of tens of meters, the 532 nm will work for DCG like a charm. Will do silver halide too obviously.
With "ferric gelatine" the exposures are too long (10's of minutes).
There are plenty of blueray threads of the holography forum; it looks like the diode can be stabilized with a good TEC and hopping it comes from a
"good batch", it'll work for holography. However, at this frequence (405 nm) some objects start to have fluorescence.
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