A Crystoleum comprises a print stuck to a curved glass, the back of the print is rubbed away and oil applied making the print transparent. Fine detail is then applied in oil colours to the back of the print. A second similarly shaped glass is attached to the back but with a small separation. On the second glass broad areas of colour are applied. Finally a card is stuck to the back and all the components are bound together.

Kromograms are for use with the Kromskop viewer developed by Frederic E. Ives in 1895. A Kromogram comprises three monochrome transparencies printed from three-colour separation negatives which are taped together. The order being red image, blue image, green image with a label and caption between the red and blue images. They were produced for both stereo and mono viewers.

The Kromskop was one of the earliest commercial applications of colour photography; as well as the Kromogram images, viewers and projectors were sold by the Photochromoscope Syndicate. Repeating backs and accessories were available enabling photographers to produce their own Kromograms. The Photochromoscope Syndicate was founded around 1897.

There are alternative spellings for 'Kromskop', the 1895 British patent uses Photochromoscope and Chromogram for the image.

The Joly process was the first screen-plate process, it was introduced commercially around 1895 but without much success due mainly to the lack of fully panchromatic plates and the width of the lines ruled on the screen. It was a separate screen process; different screens were used for exposing and viewing the image, the exposing screen having a slightly wider bandwidth.

Outline of the process

Manufacture

Patents

The image on the right shows the colour screen, taken with a microscope magnification of 48x.

The Autochrome plate was an additive transparency process. Introduced in 1907 it remained on sale until around 1933. For further information see Autochrome.

The image on the right shows the colour screen, taken with a microscope magnification of 48x.

Agfa Farbenplatten was an additive combined screen process with an irregular pattern of dots. They were similar to Autochromes but had no gaps between the dots. The plates were used in a similar way to Autochrome, development was by the reversal method. An orange filter was used at the taking stage.

The plates were developed during the First World War in Germany and introduced in Britain in 1924. According to Friedman the process is based on the patents of J. H. Christensen, E. J. Wall notes that there is a difference between early plates and those sold following the war. The process remained available until replaced by Agfacolor Neu in the mid 1930s.

Both British patents (listed below) cover the production of the mosaic screen, in particular the formation of the coloured particles by emulsifying one (coloured) liquid in another. The first patent mentions emulsifying shellac (or similar) solutions, dyed red, green and blue, in separate solutions of turpentine. The emulsion grains are drawn off mixed together and poured on a plate coated in lac, the plate is then warmed and subjected to pressure. The second patent notes improvements to the process that results in particles of a more uniform size, it mentions dextrine (or similar) as the coloured solution emulsified in gum dammar. After emulsification the gum dammar is removed by repeated dilution in turpentine and then benzine.

Based on the patents of Louis Dufay, the Dioptichrome process was introduced in 1909 as a separate screen process. During exposure the screen and plate were held in a spring-mounted frame. The same screen was used for taking and viewing. Development was by the reversal method. The following year a combined screen process was introduced.

The image on the right shows the colour screen, taken with a microscope magnification of 48x. The solid vertical bars should be yellow the squares making up the rest of the pattern should be red and blue, i.e. alternating red and blue bars with overlaying yellow bars.

This is a colour process using a regular pattern screen developed by George Sydney Whitfield of Paget. A separate screen is used allowing the negative to be processed in the normal way and for the transparency to be made by contact printing. A different screen, with modified colours, was used for viewing the transparency. The process was introduced in 1913, re-introduced following World War I and discontinued around 1925. From 1925 the old-established firm of C. Baker in Holborn advertised a very similar process. The process had a speed of around 15 Watkins, F24 Wynne.

The method of producing the screen was patented in 1908, other related aspects such as the use of a registration device on the screen and the production of prints were also patented.¹

The colour screen consisted of red, green and blue squares with twice as many blue squares as red or green. J.H. Pledge measured the squares as being, on average, 1/400 inch for the side of the blue square and 1/300 inch for the green and red squares.²

For a short period around 1914 a combined plate version was sold as was a process for producing paper prints.

In use a panchromatic plate is exposed behind the Taking Screen. After development a positive plate is made, by contact printing, which is viewed in register with the Viewing Screen. Special plates were sold by Paget for the negative and positive plates. A light filter was used over the lens when making the original exposure.

The image on the right shows the colour screen, taken with a microscope magnification of 48x.

Dufaycolor films were introduced for still photography around 1935 and for cine use a few years earlier. It was an additive combined screen process with a regular screen pattern. Dufaycolor was comparatively easy to use and so proved popular, it remained on sale until the late 1950s. This process was developed from the earlier Dufay Dioptichrome process.

The image on the right shows the colour screen, taken with a microscope magnification of 48x.

Agfacolor was an integral tripack process introduced in 1936.

This was a subtractive printing process, introduced around 1900, for the production of lantern slides and transparencies. Colour separation negatives were produced in the normal way through red, green and blue filters. The negative taken with the red filter was printed on to a photographic plate and chemically converted to a blue/green colour. The green and blue negatives were printed on to bichromated gelatine, containing silver bromide, coated on a celluloid base. The negative being in contact with the celluloid. These were developed in warm water to remove the unhardened gelatine and then dyed in the complimentary colour to the filter used at the negative stage (the image from the green negative was dyed magenta, that from the blue negative was dyed yellow). The three images were then superimposed and bound together, Canada Balsam was sometimes used between the layers.

The Sanger-Shepherd company sold all of the equipment and supplies required for both the printing process and to produce three-colour separation negatives.