Fixer

In silver Photography, the fixing is a chemical solution used at the end of the development and which makes it possible to completely desensitize a film or a photographic paper, this by eliminating the remainders from Halogénure S of money contained in the emulsion. It makes it possible thus thereafter to expose to the light a film or a pulling developed without risk to veil it.

Principle of the fixation

The shelf life of the tests or photographic films insolated depends mainly on the effectiveness of the fixation. This operation makes it possible to eliminate, most completely possible, money salts by transforming them into water soluble salts (what implies consequently an effective rinsing in complement of the fixation).

When the fixation is incomplete, one observes with the wire of time the appearance of a yellowish veil due to the reaction of the Lumière or certain gases on money halides. If the fixation is completely absent, the film or paper becomes gradually completely black and opaque.

In the case of a film, the fixation also makes it possible to remove an opaque milky veil which belongs to the emulsion. The presence of this veil after a complete development is sign of an insufficient fixation due either to a time of too short fixation, or with an out-of-date fixer. Caution: a veil absent does not mean however that the fixation is perfect. The manufacturers in general advise to fix during at least 2 times the time necessary to make disappear this veil.

Use

The fixer is generally bought in the trade, either in concentrated liquid form, or out of powder. Dilution varies in general from 1+4 to 1+9 according to respectively that one wants to fix film or paper (see the note of each model for more precise details).

Standard models are currently:

  • Ilford Rapid To fix & Hypam To fix
  • Tetenal Superfix & Superfix Odorless

Formulate

It is also possible to prepare oneself a solution of fixer. Here a traditional formula of type hypo :
  • Thiosulfate of sodium: 200 to 400 G (in general 250 G)
  • Bisulfite of sodium (liquid with 35° Baume): 50 ml (100 ml if 400 G of hyposulphite)
  • Lastly, of water in sufficient quantity to obtain 1000 ml of solution

See too

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