A darkroom is a given space, usually a separate area in a building or a vehicle, that is made dark so as to allow photographers to use light-sensitive materials to create photographs.
A darkroom must be completely dark when handling undeveloped film. Film processing must be done in total darkness, unless the film is first loaded into light-tight tanks for processing in room light. This is the method I have always used.
However, a darkroom is generally not totally dark when making black and white prints. Silver gelatin print papers are only sensitive to blue or green light, so black and white darkrooms feature a specially made red or amber colored light, known as a safelight. Safelights are not very bright, but give off enough illumination to enable the printer to see what they are doing, without exposing the paper.
The heart of the darkroom is the enlarger – an optical apparatus that projects the image from a negative onto a sheet of photographic paper. It is during this exposure that the photo can be modified, mostly by burning (giving more light to specific parts of an image by exposing it while blocking light to the rest) and/or dodging (reducing light to a specific part of an image by blocking light to it). After exposure, the photographic paper is chemically processed, or developed into the positive print.
I have been doing my own darkroom work since high school and I am now retired. I started in the hall bathroom of my parents’ house. After college graduation and the first job, I moved into a rent house that had a darkroom; and then I built one in another rent house, one for an employer, and three in houses that I’ve owned. The following is information on each facility.