Agitation helps remove the by-products of development from the surface of the film so that fresh developer can act on the exposed silver halide in the emulsion. Because agitation affects the rate of development, particularly in high-density areas, you can achieve consistent negative quality only if agitation is uniform over the whole surface of the film, and when the degree of agitation is similar for each film or batch of films. Start the timer. In the dark, carefully place the loaded reel into the developer solution. Quickly attach the top to the tank.
Air bubbles can interfere with development and produce low-density circles on the film.
Provide initial agitation of up to 5 cycle, depending on your results. For an invertible tank, one cycle consists of rotating the tank upside down and then back to the upright position. With tanks that have a handle for turning the reel, rotate the reel back and forth gently through about one-half turn at a rate of one cycle per second during the agitation intervals. Steps 2 through 4 will take approximately 7 to 20 seconds, depending on the type of tank. Let the tank sit for the remainder of the first 30 seconds.