Albumen paper
The albumen paper was one of the most popular copy papers until 1900 . The process was presented and described on May 27, 1850 by Louis Désiré Blanquart-Evrard (1802–1872) of the French Academy of Sciences. The albumin paper enabled more detailed and cheaper photographs than the previously common methods of calotype , ambrotype and daguerreotype and resulted in a warm image tone. Even modern copier papers cannot achieve its wealth of detail.
If the albumin paper is coated again with egg white (i.e. ovalbumin ) after development , it gives images of high gloss. Covered with starch ( arrowroot ) it provides dull images. Albumen paper was used - and is still used in artistic photography today - because it can reproduce the finest details.
Manufacturing
To produce the albumin paper, egg white is beaten into foam with ammonium chloride solution (“chlorammonium solution”) and the sheet floats for one minute on the clear liquid that separates out of the foam. The dried paper is placed on a solution of silver nitrate in the darkroom , where it is impregnated with silver chloride ("chlorosilver") and silver nitrate, and dried.
The negative is placed with the collodion side up on the glass plate, which forms the bottom of the so-called copy frame , the paper is covered with its sensitive side down on the negative and the copy frame is closed so that the paper is pressed firmly against the glass negative. Then you turn the frame around so that the negative is facing the light and leave it in the bright daylight until all parts of the picture are clearly visible. For development, the image is washed out with water in order to wash out the unexposed silver nitrate still in the layer. This is followed by a treatment in the so-called clay bath, a solution of potassium tetrachloroaurate (III) ("gold chloride potassium") and sodium acetate (" sodium acetate ") or sodium tetraborate ("sodium borate") in water. The red-brown tone of the picture is transformed into a purple-blue; but you can also get other nuances by changing the bathroom appropriately.
The toned and washed-out picture is fixed in a solution of sodium thiosulphate ("hyposulfurous soda", i.e. fixing salt) and then washed out very carefully. If the sodium thiosulphate is not completely washed out, silver sulphide ("sulfur silver ") forms, which turns the image yellow. The dried pictures are then cut to fit, glued on and smoothed between rollers (satin finish).
Albumin paper was industrially producible and a large part of the world production was made in the Dresden albumin factories. In 1888 the production output reached almost 9 million sheets in the format 46 × 58 cm.
literature
- Josef Maria Eder : Detailed handbook of photography. Volume 1, Part 1: History of Photography. 2nd half. 4th, completely revised and enlarged edition. Wilhelm Knapp, Halle (Saale) 1932 (reprint. Haupt, Aachen 1980).
- Gerhard Ihrke: Timeline for the history of photography. VEB Fotokinoverlag, Leipzig 1982.
