A New Direct Positive Photo-Offset Process for the Duplicating Field.

The growing popularity and importance of the direct positive diazotype process can be ascribed to a considerable degree to the variety of originals which can be photo duplicated without preparation of a special master. The common denominator of the increasing number of business systems being built around the diazotype process is the translucent paper original which presents no special problems in filing or in addition or deletion of information on the master. Since a considerable number of duplication applications require more copies than can be economically produced by the diazotype process, research at Ozalid for the past six years has been directed toward producing an inexpensive direct positive photoplate for offset duplicating machines. The sensitometric properties required for such a plate and the means by which these were experimentally realized are discussed. It is shown that by utilizing an entirely new photomechanical procedure, a plate of extremely high printing speed and contrast in obtained. The differences between this plate and conventional negative-working plates together with the resulting field problems are discussed.