Blaupause

Blaupause is a German term that originally referred to a reproducible blue-and-white copy of technical drawings, commonly known in English as a blueprint. The word also denotes the cyanotype-based printing process used to produce these copies and, more broadly, a plan or master copy.

The Blaupause process was developed in the 1840s by Sir John Herschel, who discovered cyanotype chemistry. In the typical procedure, a sheet of paper is coated with light-sensitive iron salts, and a drawing on translucent paper is placed in contact with the coated sheet and exposed to ultraviolet light. After washing and drying, the exposed areas turn blue while the unexposed lines remain white, yielding a high-contrast, durable image. This allowed rapid, inexpensive reproduction of architectural, engineering, and construction drawings.

Blaupausen were widely used from the mid-19th century through the early to mid-20th century. They facilitated sharing plans with clients, contractors, and authorities. With the advent of new reproduction technologies such as diazo and photocopy methods, the use of true blueprints declined, and the term gradually became historical or metaphorical.

Today, Blaupause persists in German as a general metaphor for a plan or schematic—a blueprint for future work or a reference model. In everyday language it can denote a rough draft or standard plan, even as modern terms are used for current reproduction technologies.