Autochromes...

I'm not a snob -- if use of a regular screen makes the result a Dufay instead of an Autochrome, it's still (assuming it works) a means of making color images on film after only B&W film is available (a situation I now believe will occur within my lifetime, if not within the next decade). I might point out, however, that it should be possible to simulate a random-dot stochastic screen with a printed output. There may be some advantage to a random pattern, in that it will avoid moire and similar artifacts when regular patterns are photographed with a system that uses a regular screen (why do directors still allow striped suits on television?).

Speed loss may be slightly mitigated by the fact that the black matrix needn't cover as much (if any) of the film area as it did with original Autochromes (the example posted must be one of the later varieties; earlier ones were about 30% black, from images I've seen). If one can tailor the dye droplet size (as in fact some enhanced resolution printers do), it might be possible to arrange for 100% coverage of the working surface without requiring any black ink/dye at all.

I think Ole meant to use the emulsion lifted from the film as a permanent coating on the glass -- essentially a means to use modern high speed pan emulsions to recreate Dufay or autochrome with the filter layer under the sensitive layer. Water would be a bad way to approach this, as it tends to dissove out the sensitizing and panchromatizing dyes (film that's been damp before exposure will show dark and light areas where the dyes have dissolved away and redeposited, changing the film speed locally). From the description, I won't want takamine anywhere near me; I'd rather grind pyro by hand in a closed room.

Donald, I agree with your comments completely.

I would add that my only concern with an irregular screen is the difficulty of creating a removable screen that can easily be reregistered. A regular screen can be registered in any number of positions.

Also, I find that lenticular screens are available for some applications such as 3D imaging of printed images, and these might be applied to the project in the fashion of the old Kodacolor lenticular film. A less elegant approach, but materials might be purchasable from the right source that would do the job right off. And, speed loss is minimal.

PE

Pe has a good point, as a lenticular screen would work.However, i do not think that this is the direction that we necessarily want to go at first, although we can go there second...

Would it be possible to put a gelatine coating over the emulsion on existing film without significant effects on the current emulsion, before exposure?

Placing a gelatin coating over a current emulsion would be a trivial exercise and would not harm the film in any way as long as it is done uniformly and the film is dried under the proper conditions to prevent water marks and migration of chemicals. I have actually done this.

You will need gelatin (about 10% of BI ~175 at a guess) with a hardener such as formalin or glyoxal at 3 - 10% (about 1 ml / 100 ml of gelatin solution) and surfactant (TX200 about 0.1 ml / 100 ml of gelatin adjusted to get good spread without repellancy - this will vary with film type). I would use a spread level of about 2 mil thickness to start and I would coat at about 40 deg C. As BI goes down, use less hardener, and as BI goes up, use more hardener.

PE

My question about the gelatine stems from this:

I was thinking that if dyed starch particles could be suspended into the gelatine, they could be easily coated onto the film. I'm not sure how feasible this is, though I see no reasin that it wouldn't work. I'll try to hack something together between now and this weekend.

Any feedback on this idea?

What you suggest would require a thicker layer than I describe above, at least as a guess, but it could work. Development rate would probably be slowed down by a large amount as well.

Give it a try.

I can coat a 4x5 overcoat on a 5x7 sheet of film in this manner with good uniformity, and that might be in the league you are talking about. You would have a 'good' 4x5 center on a 5x7 sheet. The leading and trailing ends of the coating would have startup and end defects. That would be average for this type of hand coating operation.

Another option is to coat a 3 inch wide overcoat on a 4x5 sheet of film. This would give you a 3x4 section of good overcoated film.

I have equipment to do either.

Soon, if things go as planned I will be able to do up to 8x10.

PE

PE, I really think a removable screen, to be reregistered after processing, is severely violating the KISS principle for this goal -- but the real rule (as stated by none other than Dr. Who) is: "Make things as simple as possible -- but no simpler!" I think registration is a solvable problem using the systems (still obtainable, new!) used for registering overlays and masks -- I think their original market is for cel overlays in animation, but they're used in B&W and color darkrooms for contrast masks, unsharp masks, dodging masks, etc., to ensure that the mask film is returned to precisely the same position relative to the original that it had during mask exposure.

That done, the "lenticular' overlay might need be nothing more than an acetate OHP transparency with a suitable pattern printed on it, and need no longer be water resistant (since it will be separated during processing); this would, however, require a registration system in the film holders.

A gelatin layer suspending starch grains would need to be coated to a thinness that avoids overlap, something close to the dimension of the average grain -- which varies depending on the type of starch you use (tapioca starch commonly comes in grains as big as baby peas); also, suspending starch grains in a water-based carrier like gelatin would seem prone to dissolving the starch, or at least breaking down the "sharpness" of the grains. In addition, one might need to dye the carrier gelatin black to avoid loss of saturation from unfiltered area on the film, and since both gelatin and starch would normally require water soluble dyes to take the dye well, there are likely to be issues with both dye transfer between starch and gelatin, and with all the dyes washing out during processing.

Ack, another requirement for the dyes, if they're to be applied over an existing emulsion -- they need to stand up to permanganate, dichromate, or copper sulfate reversal bleach (any of those in a 1% or so sulfuric acid solution). I don't know how strong sulfuric acid needs to be to denature starch, but I don't think I'll like the answer. Permanganate and dichromate are likely to be similarly hard on some dyes, though C-41 and E-6 bleach (both dichromate, AFAIK, at least in commercial systems) don't hurt the dyes deposited by the color developers in those processes.

I do agree as to the problem of keeping the dyes in hte starch during porcessing. This may be an issue, along with the fact that the starch may dissolve. THis was not a problem in hte original autochrome plates because the starch grains were protected under a layer of impenetrable varnish...

However, last night I was reading the Lumiere's original US patent for the Autochrome plates. It mentiones in the section about composition of the screen material that many different substances could be used. Besides starch, it suggested "ferments or levens" (yeast), "bacillus" (rod bacteria), or porcelain. The last one interested me. FInely ground glass or porcelain that is precolored may be a good solution. Although it may be problematic to grind it that finely, little pieces of glass / porcelain would solve the dye stability and bleach durability problems, as they are color through a non-dye process, and withstand sulfuric acid, and almost any other chemical substance easily (hence the ubiquitous glassware in laboratories...)

Also, does anyone have a formula for a reversal bleach? I have done reversal processing, but not with bleach that I prepared. Copper sulfate bleach would be preferable, as i have used it before and copper sulfate is quite easy to obtain.

Just a few notes here.

Acid solutions usually will not bleach azo dyes used for colorants, unless there is a catalyst present as in Ilfochrome paper bleach. So, we have no worry there.

Any non-rehalogenizing bleach used for reversal films should work just fine. Types include permanganate, dichromate and copper. Ferricyanide is usually most efficient as a rehalogenizing bleach.

The dye / starch layer has to be a monolayer, of course, or dye grains will obscure each other. Ideally, the layer should be no thicker than 1 grain when dry, or if the grains are 1 micron, then the dry thickness should be 1 micron QED.

IIRC, there was such a thing as 4x5 holders with a provision for registration of more than one sheet of film. Do I remember this right? IDK, it has been a long time.

Lumiere did indeed patent the use of dyed yeast spores and other organisms for use in Autochromes. They never reduced it to a salable produce AFAIK. Friedman describes this in his book, mentioned above.

Colored glass powders can be obtained in rather small sizes. You can also grind your own using a ball mill. In fact, use of a ball mill may be the best way to produce the dry dyed powders, and may even be needed to disperse the particles in the gelatin or varnish before coating. Ball mills are handy things to have for doing this sort of work.

An aqueous overcoat is probably the only way to get a process permeable overcoat. If you do that, the dyes can be mordanted onto the starch grains, or they can be glass beads. There are polystyrene beads in micron sizes that can be dyed with organic dyes. I have worked with some of these. They come packed dry as a fine dust that is to be dispersed in a medium. They can also be expanded like popcorn by heating gently in a microwave. They expand to mm sizes from micron sizes IIRC. I have not worked with them for years though. They would absorb organic dyes from a solvent quite well, I expect, and can be dispersed in gelatin using simple dispersion making techniques such as ultrasonics or a mixer such as made by Polytron.

PE

Use of glass or poly beads as dye filters raises issues with permeability as well as with potentially black-dyed gelatin overlapping onto irregular or spherical filter particles and darkening the matrix unnecessarily (and thus both reducing film speed and raising Dmin on the finished chrome).

The Lumiere process, IIRC, also inolved rolling the matrix after application to the glass, which flattened the starch grains (making them wider than they were thick), forced the black matrix into the interstices and off the surfaces top and bottom, and enforced a monolayer thickness. Doing this with glass filter material over an existing emulsion would be a Very Bad Thing, as it would drive the corners of the glass into the original gelatin and damage the coating exactly where it will be exposed.

There are also issues with all these methods regarding how to get a high enough percentage of the introduced filter material (starch, poly, glass, or whatever) into the gelatin matrix for coating; for best efficiency, the gelatin needs to comprise the smallest practical percentage of the matrix layer (since the more black you have, the lower your film speed and higher your Dmin) -- but the less liquid you have in a liquid-powder mixture, the harder it is to evenly coat and wet all the powder (and I'd expect this to go about 10x for gelatin as a substitute for liquid). I'd be amazed if you could make a practical filter layer with either glass or poly microbeads in gelatin, and it would work with starch (I think) only if you include enough water to soften and swell the starch as well as the gelatin (and then the above mentioned problems with dye crossover and washout recur).

I have to say, of all the ideas I've heard put forward in this thread so far, the only ones that seem at all practicable (to me) using existing film are my original inkjet dye matrix and the overlay screen with pin registration.

You may be right with what you've said, Donald, but the only way we can find out id experimentation. After all, we wouldn not have the advanced photo materials we have today if people didn't experiment with ideas repeatedly. I am working on finding replacement dyes for an inkjet printer that will not wash out of the gelatine.

I once again ask for a reversal bleach formula...

Donald, glass filler materials, properly ball milled, are spherical or nearly spherical particles. This is what the ball milling is for, like milling gems to smooth them. They probably will not penetrate the emulsion layer. In fact, this is the way Titanox and Baryta are made and placed in or on the paper supports we use today.

The carrying power of gelatin is about 1:1 for many materials, ie, for every gram of gelatin, it can carry about 1 gram of suspended solids if they are properly prepared and dispersed.

A layer of about 100 mg/dm sq would carry about 100 mg of gel and 100 mg of suspended materials, but the amount of dye, not the solids would determine the density. Glass might be ideal. IDK.

I agree that the only practical way to approach this is trial and error of as many new ways as possible or duplication of previous methods. The printer approach may very well be the best. It sounds quite interesting to me.

Herewith the official Dufay color bleach:

DF-R-2 permanganate bleach

Water to make 1000 cc
Potassium Permanganate 3.0 g
Sulfuric Acid, conc 10.0 cc

Time of treatment is 4 minutes. The film must be hardened in an alkaline formalin hardener before bleaching, and must be cleared in a clearing bath after bleaching. If you use a bichromate bleach, you may omit the clearing bath.

This is from Dufay processing instructions circa 1941.

PE

A separate color mask could be permanently mounted into a large format camera and then the film sandwiched up against it somehow for the exposure. Perhaps an in-camera vaccuum back to get a good contact. I've seen some astrophotographers that have used battery powered fishtank pumps with drilled out film holders into vaccuum backs. Then you just need to reregister the film with another screen for display after processing.

Kirk - www.keyesphoto.com

If nothing else this would be a good way to test dyes different, dye carriers and exposure.

Oops I promised just to lurk...

I was experimenting with a Dell photo printer this afternoon, printing on some old, completely blank 120 neagitves (leftovers from a previous [failed] experiment). It is quite a trick to get a good, multicolored mask to print onto gelatin. If the gelatin is slightly moistened first, the inks will adhere perfectly. (This is, of course, using standard inks). However, I have not been able to find a way to get the proper color distribution. I'm thinking that disabling the black cartridge will be beneficial to this.

My weekend project will consist of trying to engineer some new inks for my printer, and, hopefully, attempting to dye starch grains.

I was also thinking - why not use Maco IR 820c aura for this? It does not have an anti-halo backing, and, as such, we should be able to coat a mask of anything onto the back, seal it, and expose the film through the base.

What are the red and green sensitivities of the Maco IR 820c? It may just be blue and IR sensitive. Some IR films are built that way. If it has no red and green sensitivity, it will have to be redyed or it will be useless.

PE

Looking at a sensitivity plot, Maco IR's red sensitivity is excellent, as is its blue sensitivity. However, the sensitivity is low in the 450 - 550 range.

The plot is shown here...
Dead Link Removed

I'm not sure if it'll be possible to balance the screen for the deduced green sensitivity because its green sensitivity is so low. The fact that its UV sensitivity is almost as great as its infrared sensitivity might cause a problem, though.

In addition, regardless to the relative sensitivity of the film to certain wavelengths, it is an overall slow film.

In my internet research, it seems that if we want to use a permanent mask on a pre-made film, it would be best to either go inkjet or use one of the maco films with the water-soluable anti-halation backing on the film.

Also, i've been thinking of hte idea of a reregisterable mask. If the mask were to be registered with the film, and its position maked with, say, pinholes / and or notches cut into both film and mask at the time of initial registration, it would not be difficult to properly re-register after processing

I agree. Thats a good IR film, but a bad panchromatic film for this application.

PE

But you could make a nice false color IR film with it. I think the art world is aching for a "new" "handmade" process and this would fit well.

Kirk, a good false color IR film is Green, Red and IR sensitive. This would not fit the requirements for classic false color IR. However, for a real treat try cross processing Ektachrome IR film. That is quite unique and is a real Alternative Process that few have ever seen.

PE

I don't know how you'd make a false color IR film, as you'd have to use different wavelength ranges of IR to do that ... and then you's have to use IR bandpass dyes, which would get expensive, and you wouldn't be able to view the plate with the human eye, as hte dyes would appear black. You may get some IR effect if you were to use dark red grains in some places, though.

It would make a cool false colro non-IR film, though - and that's a great idea.

It might be fun to try this, using the original coating methods (coating, in order, glass, starch, varnish, emulsion) with an orhochromatic or orthopanchromatic (UV, Blue, Green, Yellow, slight orange sensitive) emulsion, which could be a commercial liquid emulsion with added dyes.

Traditional false color IR films use the Green layer to reproduce Yellow, Red to reproduce Magenta, and IR to reproduce Cyan. There is no blue record, as it is filtered out by the yellow-red filter recommended by the manufacturers.

Everything is shifted by about 100 nm bathochromically in reproduction. This is advantageous in detecting man made objects among natural objects as their IR emissions differentiate between them.

Common lenses do not transmit enough UV to make UV films useful unless you have quartz lenses such as made by Nikon. Film has the sensitivity, and gives us a 'haze' from UV, but that is near UV, not the interesting 'far' UV.

But all of what you say would be fun. Well, come to think of it, it is all fun or we wouldn't be doing it, right?

PE

Results of Weekend Experiments

I started timkering this weekend to see what I could do. I was able to do a few things:

1. Extract potato starch from potatoes. Although I was moderately succesfull at this, I learned after two hours of making realld disgusting potato paste in my blender that it is more efficient to buy this starch prepared. It is under $10.00 / pound when purchased prepared; the problem is finding it.

2. Print a screen for a DufayColor - like process. This was quite easy to do, using Photoshop to create a screen (either lines, random noise, or halftones) and balancing it to be a neutral grey. I then printed it on my inket and on a color laser Both should work, if they can be regisered / reregistered to the film. I need to get a roll of 120 film to test this out, as I am completely out of black and white film [arrgghh].

3. It is VERY DIFFICULT to coat a monolayer of tiny particles onto anything, if you want full coverage of the surface. Using glue spread onto a plastic sheet, I attmepted to spread particles of various starches and other substances onto a sheet. If they are mixed into the glue first, and then spread, good coverage of a surface is easy, if not guaranteed. However, the coating is quite far from a monolayer. If the substance is sprinked [for lack of a better technical word] onto the surface, both even converage anf obtainig a monolayer are quite difficult.

4. Ink from fiber markers (sharpies in my testing), dissolved in acetone (nailpolish remover found in medecine cabinet - oh yes for usage of pure chemicals ) ), and deposited on a surface is quite water-fast. However, usage of hte dye from an entire marker is needed to make the inks dar enough to provide significant satuartion with small droplets. In addition, it is alarmingly thin to use in printers, and has little to no surface tension. It is a start though.

5. This process will not, in any way, be anythting close to simple.

This brings me to one question: I am stilll pondering the idea of shooting through the base of a film with removed anti-halation layer. Does anyone know of films that are panchromatic and available in either 120 or large format that have either no anti-halation backing or a water - soluable anti-halation backing? The only films that I have been able to find are some Maco films, which have a water-soluable anti-halation backing and a clear base to boot. However, they are ISO 64, so the speed reduction caused by the screen might make the film uselessly slow. If we get the 40x reduction in speed that the Lumiere's had, that would render the film about ISO 1.5, which come to think of it, isn't that bad....

Ideas / comments / feedback / suggestions / flames [not really] would be highly appreciated.

There's always MACO IR 820c "AURA" - IR sensitive, ISO 100 in "ordinary" light, and no anti-halation backing. With that you'll end up with a ISO 2.5 or so Autochrome, which I think is a bit faster than the Lumiere brothers had...

I have considered the Maco "Aura" Film, and it at first seemed like a good idea.

There are three problems, however:
1.) The base is not clear
2.) The film's sensitivity is high in the UV / Blue / Yellow, and again in the Red / IR area. There is very little yellow green, green and orange sensitivity.
3.) The film is rather expensive, as I can only find it in sheet film form. It is about $65 for 25 4x5 sheets; $2.60 a sheet. This is an awful lot for early experiments. In addition, there is the problem that I do not have a 4x5 camera (other than Pinhole), which I think would be adding an unneeded factor to this.

If, once I figure out how to produce the screen, perhaps I could buy a sheet or two of this film off of someone for experiments...