Making a Color Emulsion
I'm creating this thread to raise interest and cull resources for hobbyists interested in creating color emulsions. That is, a color film.
Now, I realize that this is a bodacious task, and not one to be taken lightly. I make no bones about it, I've never even made a black & white emulsion! I have however, done a fair bit of reading & research and as they say, it's not the size of the dog in the fight, but the size of fight in the dog!
So the point of this thread is to start thinking about the best approaches, the availability of certain chemicals and how that might affect a hobbyist's choice of process, and generally to act as a clearing house for information regarding color emulsions.
So, first question. Is anyone out there making color emulsions?
Read post #166 of this thread.... http://www.apug.org/forums/forum205/...-flickr-5.html
Quote, "Since the last post, additional equipment has been installed (multi emulsion delivery system, new drive and pumps etc), this together with much emulsion research to produce the emulsions and blends, interlayers etc for the color reversal film (Kodachrome type) that I am working on has, and still is occupying virtually all my time."
Based off this, it'd be worth getting in touch with PR. (uh oh, PE and now PR!)
If Mannes & Godowsky could do it....
So what are the necessary conditions of a color film?
- A blue sensitive emulsion
- A blue-green sensitive emulsion
- A blue-red sensitive emulsion
Stacked in this order; blue sensitive layer facing lens.
- Dye layer
Yellow layer beneath the first blue-sensitive layer, cuts out the blue so the blue-green sensitive emulsion only records the green, same with the blue-red sensitive layer.
- A means to turn the silver-halide images to color.
The last condition has been accomplished two ways in recent history. The chromogenic (C-41/E6) method and the Kodachrome method. Using dye-couplers incorporated in the emulsion that are activated by the developer and controlled diffusion of dyes, respectively.
There are other methods of producing color from silver halide images, such as chemical toning. Several books exist that cover these methods extensively.
Emulsion makers, where do your sensitivities lie? Could you, if charged, create the necessary sensitivities?
The yellow dye later must be eradicated during processing, right?
What kind of color film? Reversal chromogenic, negative chromogenic or reversal dye bleach are all of the common types. Within those, the dye forming materials may be oil or water based. So lets try to get more specific.
I have already posted the results of a single layer dye bleach based color coating. It requires a sliver halide emulsion with a green sensitizer and a magenta azo dye. The dye must be mordanted in place by some means, or be ballasted in place.
I have also posted generic and specific methods for making the oil soluble dispersions for use in color chromogenic coatings.
You need the coupler and the silver halide in that case. If you go with water soluble couplers you need either a ballasted coupler or a mordant.
I can create all 3 color imaging layers but cannot make yellow filter layer as of yet. I have no couplers, but I do have yellow and magenta azo dyes. I have no cyan azo dye.
The real problem will be coating the required layers by hand. This will nominally be 6 layers or more for any decent imaging. My yield handcoating multilayers at EK was on the order of 30% or less due to defects in the coating process, but those that I got imaged very well. Any given single layer gave a yield of 90% or more.
The most doable. I'm of the opinion that it doesn't matter as long as you can expose it in a normal camera and have a record of the scene, in color. Whether that's negative or positive I don't think it matters; as long as it can be scanned, it can be shared with millions of people. That's what a 21st century analog product has to recognize.
Originally Posted by Photo Engineer
I hate to ask too many questions before reading all your emulsion threads, for fear of asking already-answered questions, so I'll hold off for now. But it's true that a project like this wouldn't be possible without the willingness of people like you to share your vast knowledge and experience on the topic. And I thank you!
What products utilize dye-bleach? Is this like Gasparcolor and Ilfochrome, the original Kodachrome? Forgive my ignorance.
All is not equal but you really need to see what the late Bob Carlos Clarke could do with a Black & White original. Toners and Chromogenic developers/couplers and retouching dyes. Much help from Agfa & Tetanal. His exhibition and book Dark Summer are the best example as a reference point.
But the use of chromogenic techniques & dye couplers is relevant here as that's the basis of all but Ilfo(Ciba)chrome. Ron's taken the Ciba (Ilford) route of Dye destruction, this had potential that was never fully realised, it could have yielded films the equal of or far better than Kodachrome. But the companies were complacent and didn't follow through.
So is this where the talk of azo dyes come in?
Originally Posted by Ian Grant
Ron, could you explain why you've decided to take this route over another, or wax eloquent on what you see as the best approach for a hobbyist in this day and age.
Something of real concern is the cost of these chemicals/dyes. What's the secret to obtaining these at reasonable prices and what processes can avoid the most expensive and impractical of them all?
Chemical toning is something to think about. I'm also kind of intrigued by the idea of duplitized film, that is, emulsions on both sides. Each side can be developed by floating it on the surface of a developer, and in this way the two can be different. Completely impractical?, yes probably, but intriguing?, certainly!
IDK, just thinking aloud.
Dye bleach is the most do-able of all of them and most of the materials (dyes and chemicals) are commercially available.
You will need Solantine Yellow, Solantine Pink and Chicago Blue as your 3 dyes for starters. The Chicago Blue is too short in wavelength but will make a respectable picture. You will need the 3 emulsions with 3 sensitizers. You will need a special yellow dye for the filter layer or you will need to make Cary Lea Silver as the yellow filter. You will need a mordant or a method of mordanting. I am working on this.
You will need an interlayer scavenger, and I'm working on this problem right now. It is also an chemical used in the layers and in the bleach to sharpen the image and reduce crosstalk.
You will need Ammonium Bromide, Sulfuric Acid, Thiourea and Phenazine for the dye bleach or variations on this mix.
You work from the bottom up coating and refining the cyan layer first, then the magenta + interlayer. Then you add the CLS layer on top to insure that there is no blue light exposure, and finally you coat the yellow imaging layer. You will find that due to the peculiarities of Dye Bleach that the image is sharp but very grainy and the grain pattern is the opposite of E6 films.
This is similar to Gasparcolor and Ilfochrome. Kodachrome did not use a dye bleach per se, but rather a dye formation / destruction process in the first version that was not imagewise in the bleach step.
Ron (PE) say's Dye bleach.
This is where the dye's already present and is destroyed during processing,
In a normal dye coupler process the dye is created as part of the development process, Ron (PE) has suggested a method for this as well. But as he's said you need more than hand coatings.
Getting specialist chemistry has always been an issue, you need to be a company these days with an account to get some items.
What conditions do the yellow filter layer need to meet? Again, it needs to disappear in processing, right?
Gasparcolor was only printed from color seps as I understand. Was there a reason for this? Why couldn't it be shot in camera?
I need to reread the chapter on Dye-bleach!
Dye bleach, with dyes present from the start, will require high speed emulsions to get any speed at all out of the system. This will further increase grain. I forgot that above.
This is a positive working system. You will need an aim gamma of about 1.7 for the camera original and about a 0.9 gamma for a print material. You will need up to 9 blended emulsions to achieve the right latitude for the print material to be useful.
I'm remembering these things as I go, so I may need a few posts to get things all together here. When I work in the lab things kind of "gel" for me (hahah Pun intended) but writing here, on things that are ancient (1975?) slows me down. I'm on autopilot in the lab though.