The unexposed portion of the photoresist remains insoluble to the photoresist developer. The unexposed portion of the photoresist is dissolved by the photoresist developer. Unreacted monomer can be removed from unexposed regions, leaving a relief polymeric image. This hardens the emulsion in the exposed areas but leaves the unexposed parts soft. It improves differentiation between exposed and unexposed crystals of silver halide, and thus reduces fog. The critical dose is the exposure at which unexposed resist begins to be attacked. Chemicals were then used to remove the unexposed portion. However it is very difficult to remove, and tends to outgas in an unexposed state. Previously unexposed children as well as adults were at risk of dying from the infection. The unexposed areas remain soft and can be washed away with water. This unexposed film was then processed and inspected for corona. Notably, the study had failed to identify a comparison group of "unexposed" persons. The secret s remains safe and unexposed. On the bottom is the unexposed copy film. This does not occur in unexposed individuals.