Borup 4x5 nitrate film (internegatives?);
link for preliminary google search results
The same three images taken through red, green and blue filters which are used for additive color synthesis may also be used to produce color prints and transparencies by the subtractive method, in which colors are subtracted from white light by dyes or pigments. In photography, the dye colors are normally cyan, a greenish-blue which absorbs red; magenta, a purplish-pink which absorbs green; and yellow, which absorbs blue. The red-filtered image is used to create a cyan dye image, the green-filtered image to create a magenta dye image, and the blue-filtered image to create a yellow dye image. When the three dye images are superimposed they form a complete color image.
This is also known as the CMYK color model. The "K" is a black component normally added in ink-jet and other mechanical printing processes to compensate for the imperfections of the colored inks used, which ideally should absorb or transmit various parts of the spectrum but not reflect any color, and to improve image definition.
At first it may seem that each image ought to be printed in the color of the filter used in making it, but by following any given color through the process the reason for printing in complimentary colors should become apparent. A red object, for example, will be very pale in the red-filtered image but very dark in the other two images, so the result will be an area with just a trace of cyan, absorbing just a bit of red light, but a large amount of magenta and yellow, which together absorb most of the green and blue light, leaving mainly red light to be reflected back from the white paper in the case of a print, or transmitted through a clear support in the case of a transparency.
Before the technical innovations of the years 1935 to 1942, the only way to create a subtractive full-color print or transparency was by means of one of several labor-intensive and time-consuming procedures. Most commonly, three pigment images were first created separately by the so-called carbon process and then carefully combined in register. Sometimes, related processes were used to make three gelatin matrices which were dyed and assembled or used to transfer the three dye images into a single layer of gelatin coated on a final support. Chemical toning could be used to convert three black-and-white silver images into cyan, magenta and yellow images which were then assembled. In a few processes, the three images were created one on top of another by repeated coating or re-sensitizing, negative registration, exposure and development operations. A number of variations were devised and marketed during the first half of the 20th century, some of them short-lived, others, such as the Trichrome Carbro process, enduring for several decades. Because some of these processes allow very stable and light-fast coloring matter to be used, yielding images which can remain virtually unchanged for centuries, they are still not quite completely extinct.
A carbon print is a photographic print with an image consisting of pigmented gelatin, rather than of silver or other metallic particles suspended in a uniform layer of gelatin, as in typical black-and-white prints, or of chromogenic dyes, as in typical photographic color prints.
In the original version of the printing process, carbon tissue (a temporary support sheet coated with a layer of gelatin mixed with a pigment—originally carbon black, from which the name derives) is bathed in a potassium dichromate sensitizing solution, dried, then exposed to strong ultraviolet light through a photographic negative, hardening the gelatin in proportion to the amount of light reaching it. The tissue is then developed by treatment with warm water, which dissolves the unhardened gelatin. The resulting pigment image is physically transferred to a final support surface, either directly or indirectly. In an important early 20th century variation of the process, contact with a conventional silver bromide paper print, rather than exposure to light, was used to selectively harden the gelatin. A wide variety of colored pigments can be used instead of carbon black.
The process can produce images of very high quality which are exceptionally resistant to fading and other deterioration. It was developed in the mid-19th century in response to concerns about the fading of early types of silver-based black-and-white prints, which was already becoming apparent within a relatively few years of their introduction.
...
Carbon printing is based on the fact that gelatin, when sensitized to light by a dichromate, is hardened and made insoluble in water when exposed to ultraviolet light. Because of the comparative insensitivity of the material, sunlight or another strong source of UV light is normally used in order to minimize the required exposure time. To make a full-color print, three negatives photographed through red, green and blue filters are printed on dichromate-sensitized sheets of pigmented gelatin (traditionally called "carbon tissue" regardless of the pigment incorporated) containing, respectively, cyan, magenta and yellow pigments.
...
Yellow dyed copy negatives & positives, motion picture film circa 1923-1933
http://books.google.com/books?id=86JXA-G2ovsC&lpg=PA127&ots=KoatUU1NS5&dq=yellow%20nitrate%20negatives&pg=PA127#v=onepage&q=yellow%20nitrate%20negatives&f=false
From: General nitrate negative info
https://www.imagepermanenceinstitute.org/webfm_send/302
Retouching
Retouching was sometimes done on larger sheet film formats, but not on 35mm or 120 roll films due to their small image size.
Gum dammar was used as retouching medium for imparting the necessary “tooth” onto which pencil was applied.57 Blocking out part of the image was done with red or yellow dyes like Neo-coccin or Vanguard yellow, which filtered some of the light passing through the negative.
Wikipedia - Technicolor process details (may provide leads/clues)
process 2, 1922-1928
Unlike tinting, which adds a uniform veil of color to the entire image, toning chemically replaces the black and white silver image with transparent coloring matter, so that the highlights remain clear (or nearly so), dark areas are strongly colored, and intermediate tones are colored proportionally.
process 4, 1932-1955
A single clear strip of black and white film with the soundtrack and frame lines printed in advance was first treated with a mordant solution and then brought in contact with each of the three dye-soaked colored strips in turn, building up the complete color image. This process is referred to as "dye imbibition", a technique which was commonly used in conventional offset printing or lithography but which the Technicolor process utilized on film. The final strip of film would have the dyes soaked into its emulsion and not simply printed onto its surface. The end result was a bright and clear representation of natural color.
CHROMOGENIC COLOR PRINT (C-PRINT) (may provide leads/clues)
http://www.theemptyquarter.com/index.php?p=glossary
Also known as a "dye coupler print," this process was developed in the 1930's. Colored dyes are put on the emulsion in multiple layers and are sensitized to different wavelengths of light. During development, the silver image is bleached out, leaving only the dye image. This type of print uses Type-C paper.
Color-internegatives?
books.google.com/books?isbn=0240515749...R. E. Jacobson - 2000 - Computers - 459 pages
In the former, a colour negative is printed on to colour-print material which is ... matrices for dye imbibition printing, and the production of colour inter-negatives. ... which respectively yield cyan, magenta and yellow dyes, colour reproduction ...
Portal for many digitized collections of WI historical material, hub for state digitization and dissemination effort
wow, look at all the useful info/tools these educators are willing to share!
"tile" text-image linking web-based tool
job posting for digitization specialist
coffee, **prestigious