There is a marked difference between rocking a tray rhythmically back and forth relatively quickly so that there is little meaningful agitation on the one hand compared to proper lift-and-flow agitation of the tray that allows the developer to run down the tray to the low point to achieve a homogenous mixture of fresh and exhausted developer on the other. Once mixed by the turbulence of the flowing liquid into the low end of the tray the mixture is mostly fresh developer, which flows back over the film or plate as the tray is lowered back to horrizontal.
You can achieve good agitation by lifting the near end of the tray about 1.5” (38mm) in about 3 seconds, wait about 3 seconds for the solution to run down into the low end and mix uniformly. Then lower back to horizontal in 3 seconds. Then do the same thing from side-to-side.
This works well to carry the thin layer of exhausted developer away from the surface of the emulsion and thoroughly mix it with the fresh developer to form a uniform mixture. Darkroom workers have been successfully tray processing sheet films and glass plate negatives since these materials were introduced, probably at least as early as the 1880s for glass plate negatives.
Last edited by Ian C; 12-01-2012 at 02:50 PM. Click to view previous post history.