The ozalid process is a process of printing

Printing

Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing....

 positive images on paper from patterns on film or other translucent media. It is akin to creating a photogram

Photogram

A photogram is a photographic image made without a camera by placing objects directly onto the surface of a photo-sensitive material such as photographic paper and then exposing it to light. The result is a negative shadow image varying in tone, depending on the transparency of the objects used...

, using chemically treated paper.

A transparent film with the pattern to be printed is placed on a diazo compound coated paper

Coated paper

Coated paper is paper which has been coated by a compound to impart certain qualities to the paper, including weight, surface gloss, smoothness or reduced ink absorbency. Kaolinite or calcium carbonate are used to coat paper for high quality printing used in packaging industry and in magazines...

. This sandwich is exposed to ultraviolet

Ultraviolet

Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 light. After a 15 sec to 5 min exposure, ammonia vapour

Ammonia

Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 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

Artist's proof

An artist's proof is, at least in theory, an impression of a print taken in the printmaking process to see the current printing state of a plate while the plate is being worked on by the artist...

, 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.

History of OZALID as a trademark

OZALID was first federally registered in the United States as a trademark on February 5, 1929 as a brand for light-sensitive copying and photographic papers. The registration currently is owned by R.Q.O. Holding Company, Inc. of New York, and is related to the even earlier registration of October 11, 1923 in what is now the Federal Republic of Germany. The R.Q.O. Holding Company also owns a United States trademark registration for OZALID for "copying and reprographic machines, apparatus and parts thereof."

However, compound "Ozalid Process" appears never to have been registered as a trademark, and the use of OZALID specifically for the Ozalid process using diazo compound paper is not currently registered as a trademark at least in the United States. OZALID as a mark for "machines for diazo type prints" was first registered in the United States in 1938 and is now expired. Similarly, another registration for the use of OZALID for Light-Sensitive Diazotype Papers, Cloths, Films, etc., Machines for Photoprinting Thereon, Machines for Developing the Photoprints Thus Produced and Parts of Such Machines was first registered in the United States in 1942, and also has expired.

Accordingly, OZALID may have become descriptive of the Ozalid process, and no longer uniquely associated with any one source, at least in the United States. Trademark rights, may, however, continue in the United States on a State registration or "common law" unregistered basis, even after a federal registration expires.