A radiographic film consists of seven layers:

1. The main base layer consists of cellulose triacetate or polyester, which is usually used because of its strength and dimensional stability.

2. A very thin layer that has the function of adding the emulsion layer to the main film layer and is made of gelatin and sticky materials.

3. An emulsion layer that basically consists of silver halide crystals suspended in gelatin. The emulsion layer is the most important layer of the film and is very sensitive to X-rays, gamma rays, light, heat, pressure and chemicals. The mixing rate of silver halides and its method determines the speed and other characteristics of the film.

4. A hardened gelatin layer in such a way as to protect the emulsion material and protect it from mechanical damage such as scratches and wear.

Unlike photographic films, which only have an emulsion coating on one side, in x-ray films, except in special cases, the emulsion layer is usually applied on both sides, so that the speed of the film and the contrast of the image increase, and from the time of exposure, emergence, proofing, and drying. Cut the film down.

There is a small amount of excess potassium bromide around the produced silver halide. Therefore, each silver halide crystal has a layer of negative bromine ions around it, which is called a bromine barrier.

During irradiation, this barrier is broken or weakened, and free electrons appear in the emulsion layer or enter it.

These electrons react with positive ions and revive very fine silver particles and become centers for emergence.

Each emerging center is made up of a few metallic silver atoms that cannot be seen and are known as hidden images.

The revived metallic silver in the hidden image plays the role of a catalyst, and in the presence of the emerging drug, the rest of the remaining atoms in the silver bromide grain turn into metallic silver. This process is strengthened and supported by the weakening or breaking of the bromide barrier around the seed.