Gelatin photographic film emulsions

The silver halide crystals can be formed as microscopic grains suspended in a protective colloid, usually gelatin. This dispersion, the photographic emulsion, can be coated on a suitable support to obtain photographic films, plates, and papers. 

Although polyester film, introduced by Du Pont under the trade name Mylar in the 1960s, has been added to the traditional supports like paper and cellulose acetate, the principle of photographic film preparation has remained unchanged since daguerreotype was developed. The sensitive surface always contains a silver halide crystal emulsion with a gelatin binder. Despite all the efforts to replace them, silver salts remain the basis of these emulsions, and film manufacturers still require gelatin, which they consume at the rate of 20,000 tons a year. The suppliers are few, and they are carefully selected. The world leader in this area is Rousselot, now a subsidiary of Sanofi Elf Aquitaine, with four units in Europe and one in the United States. 

I Photographic film contains small grains of silver bromide (AgBr) suspended In a gelatinous emulsion that is spread onto a flexible backing material. 

Gelatin has been used for photographic emulsions for more than 100 years. It is still the principal constituent of the binder in the most commercial photographic films and papers (Kragh, 1977). 

The testing system is suited particularly well for thin film specimens of any material whose tensile properties are affected by relative humidity and temperature such as epoxy, acrylic, gelatin, photographic emulsion, and many kinds of paints and plastics. 

Materials for use in black and white processes are obtained in the following way. A photographic emulsion is prepared by precipitating either a silver halide or a mixture of silver halides in a polymeric medium which is usually gelatin. This emulsion is then coated as a very thin layer on to a support such as film or paper. The coating is dried, and the support is cut into sizes appropriate to specific applications and stored in light-proof containers. 

Photographic emulsions composed of octahedral silver bromide grains were used in these experiments. The average grain size was 0.7 pm, or 0.2 pm. Methanolic solutions of various dyes were added to the emulsions, which were then coated at about 40 mg silver bromide/dm and at about 30 mg gelatin/dm on cellulose triacetate film base. The coated films were subjected to both ESR and sensitometric measurements at room temperature. 

The photographic process, another photoimaging technique (see also Special Topic 6.27), is still the most widespread application of photochemistry.1547 IR, visible, UV and X-ray irradiation of photosensitive silver halide (Ag + X ) crystals in a gelatine emulsion, coated on a film base, glass or paper substrate, causes reduction of interstitial... 

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