Photo developing relies on many chemicals to achieve the final product.
Processing your own negatives and photographic prints can be an enjoyable and rewarding hobby. You can exercise ultimate control of the final photograph depending upon the care you use in the darkroom. In addition to traditional enlargers, film tanks and other darkroom equipment, chemicals make up a large part of the production process.
Developer
Developer is the first step in both the film and print-processing cycle. It changes the invisible image on your exposed film or paper to a visible one. Developers usually contain a developing agent, an alkali, a preservative and a restrainer that are dissolved in water. A standard, all-purpose negative developer is Kodak D76, which produces a negative of normal contrast and moderate to low graininess. Print developers have basically the same components as negative developers and work in conjunction with specific paper types to produce different effects. Developing times for both negatives and prints determine the final output.
Stop Bath
Stop bath, while not absolutely essential, is used after the developer to stop development times and keep the exposures accurate. It also protects the next step, the fixer, from excess alkaline contamination. Stop bath usually contains 2 percent acetic acid and is poured into the film tank after the developer has been poured out. It also can be poured into a tray for print development. Both should be agitated for approximately 15 seconds.
Fixer
After the developer has done its work, the image on the negative or print is visible but still perishable. If exposed to light at this point, the negative or print will turn dark. To prevent this, the fixer sets the image permanently on the film and on the paper. The most important component of the fixer chemical is a solvent to dissolve silver halides. The solution should be acidic so that the alkali is neutralized quickly. Many fixers also contain an agent to harden gelatin. For general purposes, the same formula-with different dilutions-may be used with both film and paper. Fixing times for negatives and prints are determined by the chemical manufacturer's instructions, but if left too long in the fixer, images can dissolve. The biggest danger is not in too much fixing, but too little. If not given sufficient time to complete its work, prints or negatives will later darken.
Pre-Bleach or Bleach
In addition to developer, stop bath and fixer, a pre-bleach or bleach is also used in color print or film processing. Pre-bleach prepares the metallic silver developed in the developer for oxidation to silver halide in the bleach step. The pre-bleach also helps preserve the acidity of the bleach solution. The metallic silver is then removed through the bleach process.
Tags: film paper, after developer, both film, developer stop, metallic silver