Subtractive 3 color: Monopack silver dye-bleach, still photography
Karl Schinzel proposed a multi-layered monopack for still photography, based on the principle of the dye-bleach process which was later elaborated to a practical application with Gasparcolor.
Original Technical Papers and Primary Sources
Anonymous (1905): Schinzel: One-Plate Colour Photography. In: The British Journal of Photography, 52, August, pp. 608-609.
Aust. P. 42478/08
Coe, Brian (1978): Colour Photography. The First Hundred Years 1840-1940. London: Ash & Grant, pp. 120-121.
Cornwell-Clyne, Adrian (1951): Colour Cinematography. London: Chapman & Hall, pp. 23, 419-420, 668, 669, 698, 739.
Friedman, Joseph Solomon (1945): History of Color Photography. Boston: The American Photographic Publishing Company, pp. 94-95, 406.
“HERR SCHINZEL describes, in the current number of the “Photographisches Wochenblatt,” the following process for producing photographs in natural colours, which, he states, differs from all previous processes, in that separate component pictures are not required, but that with one plate a single exposure is made, and on this one plate the multi-coloured image is produced.
The plate is coated with a number of coloured gelatino-bromide films, which are separated by films of plain gelatine. The individual films are so coloured that a part of the incident light is. absorbed in each film, and by the addition of suitable sensitisers the absorption of the coloured rays is made as perfect as possible. For example, in using three films, the top one will be coloured yellow or orange, and obviously be sensitised for the blue violet rays; the middle one will be coloured blue or blue-green, and be sensitised for reddish orange; whilst the bottom one will be coloured red and sensitised for yellowish green. If a plate thus prepared is exposed on any subject, as part of the rays will be absorbed by each film, and by development and fixing the corresponding component parts of the picture will be produced. The development of the polychromatic picture is founded on the catalytic property of metallic silver. If a developed and fixed plate is immersed in a 2 per cent, aqueous solution of hydrogen peroxide, this will be decomposed where there is metallic silver, and oxygen set free. If, now, such dyes have been chosen for colouring the gelatino-bromide films, that they, by oxidation, are easily converted into colourless compounds, they will be bleached out where there is metallic silver. It is easy to conceive that after the removal of the silver, coloured pictures will be obtained, which will be not complimentary to, but according to, the colours of Nature.
The preparation of the plates here described naturally recalls the “three-colour plate” of Dr. Smith, of Zurich (see B.J.P., May 5,1905). Moreover, it is not essential that the oxidation products of the dyes should .be colourless. It will be quite enough if the power of the pigments to stain the gelatine is destroyed by the oxidation, and that they become soluble in water. Hence it would be possible to use comparatively stable dyes, so that the coloured images would bleach with difficulty in sun or daylight.
The polychrome image can be printed from the plate on to a sheet of white paper, prepared in the same way, but the picture will appear less brilliant than when observed as a transparency. As regards the practical working of the process,’ it should be noted that the gelatino-bromide of silver films must be “wasserecht” stained—that is to say, that the dyes must not be soluble in water— and that they must not be affected by development and fixation, or, if this the case, they must be reformed before the treatment with the peroxide. At the same time, any sensitisers that may be used which will not bleach, and whose colour does not agree with that of the films, can be removed.
The films of plain gelatine between the individual coloured films have the effect of preventing the action of the nascent oxygen developed in one film from acting on the others, and of confining the gas as far as possible to the requisite coloured film. For this last reason the top film is also coated with a transparent gelatine film. It is advisable, before treating the gelatine with peroxide, to harden it, but not so that the diffusion of the peroxide solution is rendered too difficult. It is well known that peroxide has the property of dissolving metallic silver, and that the oxidation would be brought to a premature stop. This disadvantage is obviated by the addition of a small quantity of soda to the peroxide solution. As, however, many dyes are altered by the alkalinity of this solution, it is necessary to regenerate them by immersion in an acid solution.
Briefly, the essential advantages of this process are that only one exposure is made, and the printable and more or less true-to-nature picture is produced on the negative plate. The preparation of the pictures is extremely simple, no more solutions are necessary than in the production of pictures on bromide paper—namely, developer, fixing, and instead of the toning bath the peroxide solution—for if the latter, when the oxidation process has continued long enough, is acidified, the solution of the silver is effected.
This method represents, therefore, a direct process of colour photography suitable for instantaneous work, and one in which the printable image is produced on the original plate in body colours. We learn that this process is patented in all civilised countries, and that further details are promised, which, we are sure, will be anxiously awaited. Nevertheless, it is well not to be over-sanguine in regard to the possibilities of such a process in practice. It seems that a composite plate such as that which Herr Schinzel proposes using is necessarily very slow, and instantaneous exposures will be possible only under the very best conditions.”
Anonymous (1905): Schinzel: “One-Plate Colour Photography.” The British Journal of Photography, 52, August, pp. 608-609.
The first suggestion for such a process came from the Austrian Karl Schinzel in 1905. He proposed a plate coated with three emulsions. The top layer was to be sensitive to blue light, and would be dyed yellow. The middle layer should be red-sensitive, and be dyed cyan, while the bottom, green-sensitive layer would be dyed magenta. Schinzel proposed that the exposed plate would be processed to a black and white negative, and then treated with hydrogen peroxide solution. This, he hoped, would bleach the dye in the immediate vicinity of the silver image, and in proportion to it, thus producing a positive dye image in each layer. When the silver image was subsequently chemically removed, a colour transparency would result. Unfortunately, the process did not work effectively, since the peroxide solution did not work selectively, bleaching out the dye not adjacent to the image as well. Nonetheless, Schinzel’s proposed ‘Katachromie’ process did outline the principle of an integral tripack process, and the idea of producing an image by a process of dye destruction did reach a commercial application later.
(Coe, Brian (1978): Colour Photography. The First Hundred Years 1840-1940. London: Ash & Grant, pp. 120–121.)
“History.—K. Schinzel’s “Katachromie” (Brit. Journ. Phot., 52, 1905, p. 608) was almost certainly the first monopack to be fully described.
A plate was to be coated with dyed emulsion layers. The top layer was to be dyed yellow and sensitive to blue light only. The middle layer was to be dyed cyan and sensitized to red, while the magenta-dyed layer was to be placed at the lowest level and made sensitive to green.
The negative after development was to be immersed in hydrogen peroxide, which, being decomposed by the developed silver, resulted in released oxygen which destroyed the dyes. After removal of the silver a positive image in full colour would remain. R. Neuhauss pointed out that it would in fact be next to impossible to prevent bleaching of the dye in the non-image areas (Phot. Rund., 19, 1905, p. 239). Whether workable or not, here is the first suggestion for coloured image making by catalytic dye destruction.”
(Cornwell-Clyne, Adrian (1951): Colour Cinematography. London: Chapman & Hall, pp. 419–420.)
“The first specific disclosure of the use of a monopack for the purposes of color reproduction came from K. Schinzel (Phot. Woch., 1905; Brit. J. Phot., Vol. 52 (1905) p. 608; Aust. P. 42478/08). The plate is coated with three silver-bromide emulsions colored complementary to their spectral sensitivities. The individual layers must be dyed with colors that do not bleed, and which are insoluble in water. The top layer is colored yellow and is sensitive to the blue. The second layer, colored cyan, is sensitized for the red. The bottom layer is colored magenta and is sensitized for the green. This is as clear and as definite a disclosure of a multilayered monopack for color reproduction as it is possible to make.
The pack is exposed, developed, and fixed in the ordinary manner. In this condition each layer contains a silver image of a single primary, imbedded in a layer of a complementary-colored gelatin. Upon treatment with two per cent peroxide, it is claimed that the dye in the immediate vicinity of the silver image will be bleached, and in an amount directly proportional to the image density. Therefore there remains a dye image in each layer which is the negative of the silver image. We will leave a critical discussion of the processing technique to a later chapter where we shall discuss the dye-bleach process of color reproduction. Here it is sufficient to point out that in 1905 there was disclosed completely the use of a Kuhn monopack for color reproduction purposes, thus anticipating Mannes and Godowsky, Troland, Caspar, and a host of other inventors, who have made this system the best answer so far (1943) to the problem of original exposure.
Needless to say neither the state of the photographic art, nor that of the dye industry was sufficiently advanced to allow the Schinzel disclosure to be put to practical use. It remained for Dr. Béla Caspar to accomplish this result. But the interest which it aroused was immediate, and the discussion that followed amplified the procedure. Neuhauss (Phot. Rund., Vol. 19 (1905), p. 239) pointed out that the use of peroxide was not advisable as this chemical would not discriminate very carefully between the dye lying adjacent to a silver deposit, and the dye that lay in non-image portions. Schinzel admitted the fallacy, and suggested the admixture of the emulsion with colorless substances which would afterward give rise to color formation (Chem. Ztg., Vol. 32 (1908) p. 665; Brit. J. Phot., Vol. 55 (1908) Col. Supp., Vol. 2, p. 61).”
(Friedman, Joseph Solomon (1945): History of Color Photography. Boston: The American Photographic Publishing Company, pp. 94–95.)
“Shortly after this article appeared, Dr. Karl Schinzel proposed a complete process for the making of color prints, utilizing the catalytic destruction of dyes by the oxygen released from peroxide in contact with a silver image (Brit. J. Phot., Vol. 52 (1905), p. 608; Aust. P. 42478; Phot. Woch., 1905). The disclosure is important from another point of view. It is one of the first patents which contains a complete description of a monopack. A plate was coated with three emulsion layers, one on top of the other, and separated from each other by plain gelatin layers. The entire group formed a single inseparable unit. Each emulsion layer was sensitized to but a single primary color, and was dyed in mass to a color complementary to its sensitivity. Thus the top layer, sensitive to the blue rays, would be dyed yellow. The central layer, sensitive to the red, would be dyed cyan. The bottom layer, sensitized to the green, would be dyed magenta. Therefore each layer completely removed the light to which it was specially sensitized, making for complete and accurate color analysis. The dyes that were used were stable to the action of water, alkaline developers, and fixing baths, so that after exposure, development, fixation, and washing they would remain intact in the gelatin layers, together with a silver image depicting the densities due to the individual primaries. The final step was to immerse the plate in a peroxide solution. Where this substance came in contact with the silver, oxygen was released. This bleached the dye immediately about the silver. Since the amount of oxygen released depended upon the amount of the silver, the destruction of the dye followed the image density. Where there was a heavy deposit of silver, there most of the dye became bleached. Highlights in the original were recorded, therefore, as highlights in the dye image. The process gave a direct positive.
As long as one did not examine the procedure too closely, it was an excellent solution to the problem of making color prints, especially from other color transparencies such as Autochromes, etc. But the practice left much to be desired. At the time the idea was proposed, the available dyes did not have the stability to peroxide that the procedure called for, so that it was extremely difficult to prevent the bleaching of the dyes at non-image portions of the layers, a fact pointed out by R. Neuhauss almost as soon as the idea was proposed (Phot. Rund., Vol. 19 (1905), p. 239). This was admitted by Schinzel in a second paper in which he discussed several other highly theoretical procedures (Chem. Ztg., Vol. 32 (1908), p. 665).
(Friedman, Joseph Solomon (1945): History of Color Photography. Boston: The American Photographic Publishing Company, p. 406.)