Experiments with RGB-colored screens... a la Dufaycolor & Autochrome

[Photo Engineer]

You have not necessarily added a sensitizing dye. In fact, none of the components you describe should adsorb to the silver halide, but it could wash out any soluble organic preservatives. So, there may be a problem, but not the one you describe.

PE

 

[holmburgers]

Welll, no, I didn't mean to say that I added a sensitizing dye. My understanding of that passage was that the washing or wetting had something to do with losing keeping qualities. Or does water alone not have the same effect?

Anyways, I'm definitely abandoning the gelatin route and going for carboxymethylcellulose (CMC gum). It sounds like that will require no "wet" step for the release, just the initial coating/binding.

 

[Photo Engineer]

Films contain soluble metal salts and soluble organics. Washing and keeping may cause increased fog, but that would LIGHTEN the reversal photo. So, you see why I hesitate to give an answer. Things went the wrong way. Unless a development accelerator was washed out causing severe underdevelopment in the first developer. So, you see, I can't solve this except by extensive experimentation.

PE

 

[holmburgers]

I'm not expecting you to solve the problem for me PE, but let's just keep talking about it, because every sentence you write tells me something new that I didn't know before.

Interesting about development accelerators... perhaps a PM to Ilford-Simon is in order.

 

[Photo Engineer]

Chris;

I know I am not expected to solve it. Poor choice of words on my part. Sorry. I'm having trouble making intelligent guesses!

One relatively easy experiment is to cut 1 sheet in half and treat one half in your glop and etc, then expose both halves at the same time and process at the same time.

PE

 

[holmburgers]

Ilford's PDF on Delta 100 has this to say, "A pre-rinse is not recommended as it can lead to uneven processing."

++ Thank you Ron, I will certainly admit that your expertise and knowledge is far beyond anyone else who is so willing to give advice and help.. so in that respect, you are "crucial" in helping me, but to really solve it, I'd have to pay you a consulting fee or something...

Yeah right! (hehehe)

And the test is a good one. I'm reluctant to waste anymore time time on my glop though, as there are other problems involved. I should test it though, for the sake of knowing what the heck happened...

 

[Gerald C Koch]

I have read that the Autochrome process only worked because the spectra of each of the dyes was imperfect. Theoretically, the dyes should have no overlap in their spectra. But this was not the case for Autochrome. Unless you can get the same dyes used by Lumiere I think there is no chance for success. I fear that this holds whether you try to duplicate the original process or try something with todays color emulsions.

 

[holmburgers]

Err....

There most certainly is a chance for success. There's nothing that magical or mysterious about the basic principles involved here. Something only working because it was imperfect doesn't make sense to me. I think it's amazing that the color was so good in spite of that, and with purer spectra the results should only get better. Any combination of dye-colors will make 'approaches' at reproducing other hues, but good saturation is completely dependent on using the appropriate reproduction colors. At least, that's my understanding.

 

[holmburgers]

Example of Laminating with CMC Gum

This is a transmitted-scan of two fixed out sheets of b&w film, laminated together with 4% CMC gum.

The bubbles are what I'm trying to eliminate, and the main area of distress in the gum layer is due to some separation at that point.

The upper left half is what I'm striving for.

After scanning, I pulled the sheets apart without water and without much difficulty. It had been about 6 days since they'd been laminated and the inside was still slightly moist. I have no idea how long it might take until the CMC gum dries out, or what affect that would have upon the ability to easily separate them. Time will tell, but at the moment I'm having trouble getting all the gum to come off the sheets in a water wash... and I want to avoid as much abuse as possible to the undeveloped film, sooo damnitalltohell at the moment...



To be continued...

 

[holmburgers]

Keep It Simple

Ok, I can say with some certainty that I've found the perfect binding agent.

GLYCERIN

The problem with CMC-gum & gelatin was simply that it dried up and became an excellent glue. This made it incredibly difficult to separate the sheets and remove all residue.

Glycerin doesn't dry out it seems. It's sticky enough that it holds the sheets together and is also incredibly easy to wipe off. So far I've laminated just one sandwich of fixed out film, but the coating is clear and 99% bubble-free. The front of the screen wiped clean quite effortlessly with a wet sponge. Instead of hanging it up to dry, I just stuck it in my film holder.

The one caveat now is that if you're using a permanganate bleach for your reversal processing, the glycerin will need to be completely absent. Apparently permanganate & glycerin explode, or something. Luckily I use dichromate, but definitely something to be aware of.

It seems that the best solution is always the simplest one.

I plan to laminate at least 1 real screen-plate sandwich tonight; processing might be a matter of weeks, but who knows, maybe sooner.

Stay tuned...

 

[Photo Engineer]

Occam's razor!



PE

 

[holmburgers]

I just hope I don't cut myself....

 

[Photo Engineer]

Avoid Sweeny Todd!

PE

 

[holmburgers]

Oh yeah, that's a gruesome movie!

So PE, it seems that glycerin is really soluble in water. Would you 2nd that opinion? I'm thinking that a quick pre-wash at 20°C and a wipe of the sponge will be all the cleaning that is necessary... woohoo!

 

[Photo Engineer]

Glycerin is indeed soluble in water so you should not have any problem removing it. I did not know that it had enough adhesive properties to really stick the two films together all by itself.

PE

 

[holmburgers]

Yes, it's doing surprisingly well. It's kind of oily feeling, and just viscous enough that it doesn't spread too thin. Something to do with surface tension perhaps?

 

[Photo Engineer]

Chris;

If you want glycerin with different viscosities propylene glycol is a close approximation in polymer form. You can get it with different molecular weights and thus different viscosity values. Carbowax is a similar item that can be gotten as a liquid or a solid depending on MW, and the solids dissolve in water to give different viscosity solutions.

PE

 

[holmburgers]

Thanks PE,

That's very interesting indeed and I seem to recall you mentioning carbowax in the past.

But I must admit that I'm glad to (hopefully) be done experimenting with binding agents... :joyful: ...for the time being.

 

[holmburgers]

Last night I took a picture with the glycerin screen-plate and proceeded to develop it as a negative (much easier for a quick test)

Success! There is some slight unevenness around one of the edges where contact might not have been perfect, but that's all in the technique and that's going to get better.

The good news is that the glycerin binding separated very easily in water and appeared to have no effect on the processing, though a "dry-peel" is still not an option (even glycerin seemed to dry out a bit and act like a glue). Good news is, there was negligible damage to the emulsion of either sheet of film.

If you recall, when I laminted the sheets with hot gelatin, a large portion of dye was left on my registration board, suggesting some unpleaseant leaching had occurred. The glycerin though, left very little dye on the board, and a lot came out in the pre-soak, so that's good too; no lost acutance dyes.

I haven't register the two sheets yet since this was late last night and I went to bed right after cleaning up. I'll hopefully get a scan soon and post it post-haste!

 

[holmburgers]

Quick update.

So I attempted to register the negative and obtain good color. It was a challenge for 2 reasons I believe. 1 of course was simply registration in general. What I discovered was that my current registration method is flawed.

I punch the sandwich while dry. Then, I've got a board with pins, and I'm putting glycerin on the screen, turning out the lights, and then putting the b&w film on the pins in contact with the screen. The problem is that glycerin doesn't dry (of course this is good for other reasons) and when I take the sandwich off the pins, which hold onto the sandiwch a little too tightly, the sheets slide a bit and I lose registration with the punch holes. Really thin registration pins that would fit in a film holder would fix this.

SO, the obvious solution is to bind the sheets w/o registration pins, attempting to get good placement (no overlapping allowable, otherwise it won't fit in the film holder) and then punch them. In theory, this should work better, but we'll see.... I can imagine a host of new problems from this method.

The other problem was my negative, which was under exposed or under developed. At any rate it was too thin, and thus the colors are incredibly desaturated. Pastel extraordinaire! This could be a function of overall density, and/or inherent contrast.

So with my registration method being flawed, with this example at least, getting the color right was very difficult, compounded by the fact that it was a negative and I was having trouble telling when it was right. I taped the negative onto my light table and then tried to manipulate the screen until it looked right. This is an exercise in patience, believe you me...

However, there was one moment when it totally popped and I could see no moire and the color was quite good. Of course, as soon as I moved in the slightest it was lost, and so I really have no idea how to get registration and keep it.

Grr...

Oh well, discouragement is for the birds. Onwards & upwards!

 

[holmburgers]

Here is how I will create screen plates when E6 is discontinued.... gulp... (hopefully never!)

From J.S. Friedman's History of Color Photography, p. 154, ch. 'Formation of the Screen'

The ability of the photographic emulsion, be it sensitized either with dichromated gelatin or silver halide salts, to reproduce fine details, was quickly seized upon for the formation o fscreens. It was first suggested by du Hauron ("Les Couleurs en Photographie Solution du Problem," 1869, p. 54; "La Triplice photographique et l'Imprimerie," (1987), p. 336). A gelatin layer, dyed primary red, and sensitized with dichromate, was exposed through a black & white line screen, the blacks having twice the width of the whites. The action of the light tanned the gelatin that corresponded to the transparent areas of the master screen. The soft gelatin was removed by a hot water etch. This left a series of red lines, separated by transparent portions whose width was twice that of the reds. The plate was next recoated with gelatin dyed green, and sensitized with dichromate. The second exposure was also through a black & white screen, but this time the width of the two was the same, and their direction was at right angles to the red lines. [and exposed through the base] Since the red portions passed no light that was effective upon the dichromated gelatin, only the gelatin lying between the previously formed lines was affected, and of this, only one half of the total area became tanned. Hot water treatment removed the unaffected gelatin, which was finally replaced with new gelatin dyed a primary blue, and as before, sensitized with dichromate. The last exposure was made without any master screen, only through the red and green areas formed previously. These acted as opaque lines for the blue rays to which the gelatin was sensitive. Between all coatings, it was desirable to further treat the plate to thoroughly fix the dyes or coloring matter in the tanned gelatin. Hence no diffusion of colors was possible.

Brilliant!

 

[Photo Engineer]

Unfortunately, you still need a method to take panchromatic photographs.

PE

 

[holmburgers]

Of course, but I'm guessing that b&w film will be around for a lot longer than slide film.

 

[holmburgers]

But you're right Ron, I need to learn how to make a panchro emulsion!

 

[Photo Engineer]

Yes, you cannot count on analog for YOUR lifetime! Mine, maybe, but yours? Hmmmmmmm. Soon, my next interview by Scott Sheppard will be up on his site. Give it a listen!

PE