Developer solution

Developer solution is used in the darkroom for developing (i.e. converting latent image to visible image) x-ray films used in conventional (screen film) radiography.

Components

• developer: hydroquinone (for high contrast) + Metol or phenidone (for low contrast)
  • the developer itself gets oxidised and in the process reduces the exposed silver in the film to form metallic silver (black)
  • Metol was originally a brand name, and is short for "N-methyl-p-aminophenol"; it is not related to the word "metal" 
• alkali: to maintain the pH (at 10-11) of the solution for optimum work of developer
• preservative: sodium sulfite, to reduce the oxidation rate of developer and dissolve the products into sulfonates (colourless) thereby increasing its life
• restrainer: potassium bromide, prevents the developer from acting on unexposed silver (thus preventing fog formation)

Optimum temperature (20-22 C) is required for developing.

• if low temperature: increase the developing time to obtain a proper image
• if high temperature: reduce the developing time

Usual developing time is 5 minutes at 29 C, when done manually. In automatic film processors, these factors are taken care of by the processor and thus the image quality is more consistent.

Developing is followed by rinsing in water (for about 30 seconds) to remove the chemicals etc. before the film is fixed. This is followed by washing under running water and then drying.