preparation of photosensitive coatings for Lippmann photogra

This is a forum exploring Lippmann photography.
Martin

preparation of photosensitive coatings for Lippmann photogra

Post by Martin » Wed Jul 16, 2008 11:17 am

laywomen wrote:At the moment , we read a lot of literature and also old threads.
Can sombody tell us, what does "TEA" mean? Is somewhere, here in the forum, a page with all the used abbreviations?
I don't know if there's a page about these abbreviations but it might be useful (I've to admit to consider myself equally a „victim“ of the sometimes cryptic abbreviations).
Here, TEA usually refers to triethanolamine.
Are the developer (e.g. GP-2, CW-C2) commerially available or do we have to mix it on our own?
You've to mix them on your own.
For Lippmann photography process, is there a bleaching step also necessary?
Little success has been reported from bleaching.
What does the bleaching process effect?
It transforms a black metallic silver into a transparent layer of AgX crystals.
Can we use a standard fixing solution for black and white photography?
No, I don't think so. Fixing will remove too much silver salts, leading to layer collapse and hence to a large wavelength shift when reconstructing the image.
Note, the GP-type of development already includes a „fixing“ agent: e.g. ammonium thiocyanate. To some degree you can replace the ammonium thiocyante with thiosulfate („hypo“).

d paul

preparation of photosensitive coatings for Lippmann photogra

Post by d paul » Thu Jul 24, 2008 11:07 pm

Hello
There have a couple of papers published that state there is no need for the mirror coating to shoot a Lippmann photo. In short you would take your plate and load it into your plate holder with the emulsion side facing towards the back of the plate holder which is covered in black velvet to reduce reflections. Then the first silver layer is at the surface of the emulsion,rather than 1/4wavelength into the emulsion when a reflector is used.
"Lippmann photography; it's history and recent development" by Hans I Bjelkhagen is the easiest refrence ; "Silver halide emulsions for Lippmann photography and holography " by the same author is a nice overview of emulsion types and making.
I have been working at Lippmann photography for a couple of years now, with a great deal of help from Darren Green, and I haven't got to the point yet where I get good color rendition. At times it seems almost a black art rather than science, and I will follow your work with great interest
Rob

Hans

preparation of photosensitive coatings for Lippmann photogra

Post by Hans » Fri Jul 25, 2008 11:02 am

What is the coherence length of sun light? It's bigger than 7um right?

Is it not just possible to index match a plate to a front surface mirror and clamp it tightly onto it? If the emulsion is flat I would think that in that case the distance between the emulsion and the mirror is much smaller than the thickness of the emulsion.

Perhaps in the old days a preference was present for using mercury because most front surface mirrors were made with silver coatings that were not very scratch resistant and were not able to cope easily with the water required for cleaning the mirror after the lippmann plate was separated from it? But nowadays one can buy alluminized front surface mirrors.

Martin

preparation of photosensitive coatings for Lippmann photogra

Post by Martin » Sun Jul 27, 2008 8:08 am

Hans wrote:What is the coherence length of sun light? It's bigger than 7um right?
I don't know exactly but it's certainly much lower than that.
I vaguely recall the whole thing gettting more complicated when broadband sources are involved. For example, the red part of the spectrum has a longer coherence length than the violet part.
Is it not just possible to index match a plate to a front surface mirror and clamp it tightly onto it? If the emulsion is flat I would think that in that case the distance between the emulsion and the mirror is much smaller than the thickness of the emulsion.
Right. One issue though is that by index matching you're again losing precious coherence length (the light has to travel twice through the index matching layer).

Sogokon'A

preparation of photosensitive coatings for Lippmann photogra

Post by Sogokon'A » Sun Jul 27, 2008 2:17 pm

d paul wrote:At times it seems almost a black art rather than science
What fine epigraph for the chapter devoted by photographic emulsion!

In order the initial substances have to turn to products of the reaction, the reaction system should break some power barrier.
путь реакции1.jpg
путь реакции1.jpg (52.51 KiB) Viewed 7284 times
Process of ripening emulsion occurs at a room temperature (or close to it) and at atmospheric pressure. If temperatures of process all have got used to supervise carefully to variations of atmospheric pressure do not pay attention, including its influence insignificant. But in this case, when very small the power barrier, influence of pressure can appear very essential.

It is interesting, whether marked Neuhauss in the laboratory magazine the size of atmospheric pressure those days when Lippmann’s emulsion prepared? And Daren Green?
If it will be found out that fluctuation of atmospheric pressure can not explain not reproducibility of results then it is necessary to call to the aid «black art» and other "magic’s".

Martin

preparation of photosensitive coatings for Lippmann photogra

Post by Martin » Mon Jul 28, 2008 4:27 am

Sogokon'A wrote:It is interesting, whether marked Neuhauss in the laboratory magazine the size of atmospheric pressure those days when Lippmann’s emulsion prepared?
Neuhauss' journal is indeed full of hints to weather conditions during emulsion preparation.

Sogokon'A

preparation of photosensitive coatings for Lippmann photogra

Post by Sogokon'A » Mon Jul 28, 2008 9:23 am

Martin wrote:
Sogokon'A wrote:It is interesting, whether marked Neuhauss in the laboratory magazine the size of atmospheric pressure those days when Lippmann’s emulsion prepared?
Neuhauss' journal is indeed full of hints to weather conditions during emulsion preparation.
Hints it very well, but actual figures – is better … From hints scientific result you "will not squeeze out".

Hans

preparation of photosensitive coatings for Lippmann photogra

Post by Hans » Tue Aug 12, 2008 3:25 pm

Martin wrote:
Hans wrote:What is the coherence length of sun light? It's bigger than 7um right?
I don't know exactly but it's certainly much lower than that.
I vaguely recall the whole thing gettting more complicated when broadband sources are involved. For example, the red part of the spectrum has a longer coherence length than the violet part.
Is it not just possible to index match a plate to a front surface mirror and clamp it tightly onto it? If the emulsion is flat I would think that in that case the distance between the emulsion and the mirror is much smaller than the thickness of the emulsion.
Right. One issue though is that by index matching you're again losing precious coherence length (the light has to travel twice through the index matching layer).
Concerning coherence length: If I hold two clean pieces of glass together with 60um pieces of Scotch tape I can still see clear newton rings under a fluorescent lamp. So, under that type of light the coherence length has to be longer than that for the individual lines.

Would it not be more beneficial to use a index matched front surface mirror to the gelatin side of the film and live with the slight distance between them rather than content with the much lower reflection between the gelatin/air interface?

Martin

preparation of photosensitive coatings for Lippmann photogra

Post by Martin » Wed Aug 13, 2008 3:11 am

Hans wrote:Concerning coherence length: If I hold two clean pieces of glass together with 60um pieces of Scotch tape I can still see clear newton rings under a fluorescent lamp. So, under that type of light the coherence length has to be longer than that for the individual lines.
I don't know what the coherence function of a fluorescent lamp is in respect to all its lines combined.
Looking through a transmission grating, you'll notice these lines to be pretty narrow: if you remove all the lines except for one, you'll get a fairly sharp image.
Would it not be more beneficial to use a index matched front surface mirror to the gelatin side of the film and live with the slight distance between them rather than content with the much lower reflection between the gelatin/air interface?
Due to the short coherence length of white light I assume the latter would be the better solution.

Hans

preparation of photosensitive coatings for Lippmann photogra

Post by Hans » Wed Aug 13, 2008 8:32 am

Martin wrote:
Hans wrote:Concerning coherence length: If I hold two clean pieces of glass together with 60um pieces of Scotch tape I can still see clear newton rings under a fluorescent lamp. So, under that type of light the coherence length has to be longer than that for the individual lines.
I don't know what the coherence function of a fluorescent lamp is in respect to all its lines combined.
Looking through a transmission grating, you'll notice these lines to be pretty narrow: if you remove all the lines except for one, you'll get a fairly sharp image.
Would it not be more beneficial to use a index matched front surface mirror to the gelatin side of the film and live with the slight distance between them rather than content with the much lower reflection between the gelatin/air interface?
Due to the short coherence length of white light I assume the latter would be the better solution.
That begs the question: How thick is an index matching layer? From experience I know that when mold coating a 10x15cm plate with 60um spacers about 5ml of liquid gelatin is needed. But when index matching only a small drop of liquid is needed. How many ml is a small drop? Perhaps we are talking a fraction of a um with index matching. Has anyone ever tried it?

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