A minilab is typically a "Roller Transport" processor, where the film follows a serpentine path over many rollers. Each chemical processing step is done using a chemical immersion tank with replenishment to keep the Chemicals Fresh. Film advances down into the tank and then turns and rises up and out, then advances down into the next tank, and so forth. Chemical exposure timing is a combination of film advance speed and the physical length of the serpentine film path immersed in the fluid. The fluid in the tanks is usually agitated, filtered and warmed to 100°F (necessary for the C-41 process), and the fluid also needs periodic replacement. The Film processor also has a dryer, just like wet silver halide printers.