1975, they replaced the older printing methods. When large size xerography machines became available, c. Xerography is standard copy machine technology using toner on bond paper. Diazo prints remained in use until they were replaced by xerographic print processes. Other comparable dye-based prints were known as blacklines. The drawings are also called blue-lines or bluelines. This technique produces blue lines on a white background. In the early 1940s, cyanotype blueprint began to be supplanted by diazo prints, also known as whiteprints. Traditional blueprints became obsolete when less expensive printing methods and digital displays became available. To combat this problem, printing on imitation vellum and, later, polyester film ( Mylar) was implemented. Paper was a common choice for more durable prints linen was sometimes used, but with time, the linen prints would shrink slightly. Various base materials have been used for blueprints. The blueprint process is still used for special artistic and photographic effects, on paper and fabrics. By the later 1890s in American architectural offices, a blueprint was one-tenth the cost of a hand-traced reproduction. Introduction of the blueprint process eliminated the expense of photolithographic reproduction or of hand-tracing of original drawings. the history of alterations recorded on the sheet.a record of the approved specifications.The result is a copy of the original image with the clear background area rendered dark blue and the image reproduced as a white line.

The unconverted coating is washed away, and the paper is then dried. When a strong image is seen the frame is brought indoors to stop the process. Where the India ink blocks the ultra-violet light the coating does not convert and remains soluble. Where ultra-violet light is transmitted through the tracing paper, the light-sensitive coating converts to a stable blue or black dye. The frame is put out into daylight, requiring a minute or two under a bright sun, or about ten minutes under an overcast sky to complete the exposure. The tracing paper drawing is placed on top of the sensitized paper, and both are clamped under glass, in a daylight exposure frame, which is similar to a picture frame. Engineers and architects drew their designs on cartridge paper these were then traced on to tracing paper using India ink for reproduction whenever needed. This is a simple process for the reproduction of any light transmitting document. Excess ammonium ferric citrate and potassium ferricyanide are then washed away. The image is then developed using a solution of potassium ferricyanide forming insoluble ferroferricyanide ( Prussian blue or Turnbull's blue) with the divalent iron. When the paper is illuminated, a photoreaction turns the trivalent ferric iron into divalent ferrous iron. The paper is impregnated with a solution of ammonium ferric citrate and dried. The best known is a process using ammonium ferric citrate and potassium ferricyanide. The blueprint process is based on a photosensitive ferric compound. The blueprint process Architectural drawing, 1902 Architectural drawing, Canada, 1936 Practising engineers, architects, and drafters often call them 'drawings', “prints”, or “plans”. The term blueprint continues to be used less formally to refer to any floor plan (and even less formally, any type of plan). It has almost entirely been superseded by digital computer-aided construction drawings. The process is obsolete, largely displaced by the diazo whiteprint process, and later by large-format xerographic photocopiers. Color or shades of grey could not be reproduced. Blueprints were characterized by white lines on a blue background, a negative of the original. It was widely used for over a century for the reproduction of specification drawings used in construction and industry. The process allowed rapid and accurate production of an unlimited number of copies. A blueprint is a reproduction of a technical drawing or engineering drawing using a contact print process on light-sensitive sheets introduced by Sir John Herschel in 1842.

Contractor blueprint software