photographic film material

JohnWW

2004-07-24 10:59:55 UTC

I think photographic film (the substrate, not the light-sensitive
emulsion coating) is usually made out of cellulose, or a cellulose ester
derivative like cellulose acetate (made by reacting cellulose, e.g.
cotton or wood fibre, with acetic anhydride and a trace of sulfuric
acid). Other suitable materials, which I am sure have at least been
tried e.g. for large photographic exposures like x-ray radiographs,
although more expensive, would be acrylic polymers ("perspex"),
polycarbonate polymers, and polyester polymers (as used in fiberglass).
At first, ordinary plate glass was used, and indeed until relatively
recent decades for some specialized applications e.g. astronomy and
x-rays, but its fragility and weight caused problems.

Many years ago, for a time, it was made of cellulose nitrate -
"gun-cotton", made by reacting cellulose with nitric acid and a trace of
sulfuric acid. The same substance was once used in muzzle-loading
shotguns. This caused problems in the storage of large amounts of
photographic film in the form of movies - it was highly explosive, and
unless stored dry and at low temperatures it tended to slowly
deteriorate due to oxidation of the cellulose base by the nitrate
groups. Dangerous goods inspectors then had the job of inspecting movie
film for its safety.

The earliest photographs - daguerrotypes in the 1830s - were made using
a light-sensitive mercury composition coated onto glass plates. This was
replaced at an early stage with gelatinous emulsions containing fine
grains of light-sensitive silver compounds, e.g. chloride and bromide,
which darken on exposure to light due to reduction to metallic silver;
the unreacted silver compound is removed in developing with (usually)
sodium thiosulfate in the absence of light. This is still used in X-ray
radiography; but with the advent of color photography, mixtures of
various light-sensitive organic dyes which change color to the primary
colors (cyan, magenta, yellow) on exposure to light are now used in the
emulsions.

John W.

Post by Muhammad Adeel
hi to everyone
This is adeel fom pakistan. i m doing my Polymer engineering from
UET lahore. Have ther anybody to tell me what is the material of
photographic film i mean i want to study the manufacturing of
photographic flim can u tell me book or resourc?
Ur truly

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