Desensitizers

Desensitizing is a process whereby the sensitivity of a plate or film is depressed, so that the development can take place by a brighter darkroom illumination.

At the present time (1943) the following desensitizers are available:
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[wptabtitle]Desensitizers with Dyeing Properties[/wptabtitle]
[wptabcontent]The most popular member of this group is phenosafranine (Pinasafrol, Desensitol), which forms a very effective desensitizer, although it has the drawback of staining the emulsion and fingers.

For use, dilute with 4 parts of water. Immerse the film in this solution for not less than 1 minute before development.
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[wptabtitle]Coloured Desensitizers[/wptabtitle]
[wptabcontent]Though they are slightly coloured, they do not stain the film. Pinacryptol green belongs to this group.

For use, dilute with 4 parts of water, and immerse the film for 2 minutes before development.
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[wptabtitle]Colourless Desensitizers[/wptabtitle]
[wptabcontent]The latest advance in the technique of desensitization is the colourless form, such as:

Pina White:  Dissolve 1 tablet of Pina White in 20 mililiters of warm water. After cooling, pour this solution into 0.5 liters of developer.

Qualitol:  This is sold in the form of a clear colourless solution which is diluted with 20 parts of water for use. Plates or films are bathed in the dilute solution for 2 minutes and then passed into the developer without rinsing. Development can be observed by using an IIford Bright Green Safelight in which a 15 watt lamp provides light. The darkroom lamp should be some 2–2.5 meters away from the developer dish or tank.

Desensitizing Yellow:  It is sold in 1 gram tubes. The contents of a tube, a fine yellow powder, is dissolved in 1 liter of boiled water. When solution is complete the solution is made up to 2 liters with cold water and is then ready for use. Bathe for 2 minutes and then proceed as described for Qualitol.
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