Ozalid process
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In printing, the ozalid process is a trademarked method of printing positive images on paper from patterns on film or other translucent media. It is akin to creating a photogram, using chemically treated paper.
A tranparent film with the pattern to be printed is placed on a di-azo compound coated paper. This sandwich is exposed to ultraviolet light. After a 15 sec to 5 min exposure, ammonia vapour is used to develop the film image on to the paper.
Its main use was for making copies of electrical, mechanical and civil engineering drawings. It is still used widely in developing countries. It is also used for proofing, as it produces an image very close to the finished work.
This process produces a blue or black image on a white paper. It is a monochromatic copying process.
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