“The Warner-Powrie process patented in 1905 was the earliest commercial process using a screen made with bichromated colloid. A glass plate was thinly coated with bichromated gelatin or fish glue and exposed to light through a screen having opaque lines twice the width of the spaces between. The nonexposed portions of the colloid were then washed away, leaving the hardened lines which were dyed, say green, and then mordanted. The plate was again coated and exposed a second time with a screen moved to cover up the lines formed during the first exposure. Following a second washing the new lines were dyed red and mordanted. The same procedure was repeated a third time except that the exposures were made through the back of the plate with a blue filter, and without the use of the screen.1
1 Mees and Pledge, 1910, pp. 200-201; Bull, 1935a, p. 68. ”
(Evans, Ralph Merrill / Hanson, W.T., Jr. / Brewer, W. Lyle (1953): Principles of Color Photography. New York: Wiley, p. 290.)
Original Technical Papers and Primary Sources
Powrie, J.H. (1928): Line Screen Film Process for Motion Pictures in Color. In: Transactions of the Society of Motion Picture Engineers, 12,34 (April, 1928), pp. 320-334.
Cherchi Usai, Paolo (2000): Silent Cinema. London: BFI, p. 34.
Coe, Brian (1978): Colour Photography. The First Hundred Years 1840-1940. London: Ash & Grant, pp. 53-54.
Evans, Ralph Merrill; Hanson, W.T., Jr.; Brewer, W. Lyle (1953): Principles of Color Photography. New York: Wiley, p. 290.
Nowotny, Robert A. (1983): The Way of All Flesh Tones. A History of Color Motion Picture Processes, 1895-1929. New York: Garland Pub., pp. 133-135.
Ryan, Roderick T. (1977): A History of Motion Picture Color Technology. London: Focal Press, pp 36-37.