On the way there I wondered about the process of printing pictures and whether it has any relation to surface tension and this blog. It does in the last step. The photographic industry is a dying art and the companies that founded easy printing like techniques Eastman Kodak and Fuji films stakes in film are finding themselves on life support. So I thought it would be interesting to learn more about it now before it becomes too historic.
Photographic film uses a sheet of platic which is either made from nitrocellulos, cellulose acetate or polyester. An emulsion (some oil in water like for example milk) of light sensitive silver halide coats this plastic and is stuck with gelatin. Variable crystal sizes determine the sensitivity, contrast and resolution of the film. The silver halides, except for silver fluoride, are extremely insoluble in water. These salts are coated twice for black & white and about four times for color. The salts sensitivity to light and size affects the speed and resolution of the photograph.
The typical process of color film development is like this:
Chromogenic materials use dye couplers to form colour images. The film is put into water and gelatin is swelled so chemicals can react with the silver halides. Modern colour negative film is developed from one of two processes the C-41 or RA-4 process which are both similar (this is taken from Wiki):
- The colour developer develops the silver negative image. The byproducts activate the dye couplers to form the colour dyes in each emulsion layer (so possibly four).
- A rehalogenising bleach converts the developed silver image into silver halides.
- A fixer removes the silver salts.
- The film is washed, stabilised, dried and cut.
In the fourth step. The washing stage detergents like Triton X-100 or octylphenol ethoxylate are used as wetting agents to lower the surface tension of the film and prevent drying marks and making the drying even. The film is hung out to dry in a dark room. After the drying process is complete the developer looks at the film, laughs and text messages the recipient. The recipient comes down with excitement in his eyes only to be disappointed by the outcome of the pictures.
P.S. Could it be possible to reviving film to make Harry Potteresque pictures using electronic inks?