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A blueprint is a reproduction of a
technical drawing
technical drawing
or
engineering drawing An engineering drawing is a type of technical drawing that is used to convey information about an object. A common use is to specify the geometry necessary for the construction of a component and is called a detail drawing. Usually, a number of ...
using a
contact print A contact print is a photographic image produced from film A film, also called a movie, motion picture or moving picture, is a work of visual art used to simulate experiences that communicate ideas, stories, perceptions, feelings, beaut ...

contact print
process on light-sensitive sheets. Introduced by Sir
John Herschel Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor, experimental photographer who invented the blueprint, and did botanical wor ...
in 1842, the process allowed rapid and accurate production of an unlimited number of copies. It was widely used for over a century for the reproduction of
specification drawings
specification drawings
used in
construction Construction is a general term meaning the art and science to form Physical object, objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Pre ...
and industry. The blueprint process was characterized by white lines on a blue background, a negative of the original. The process was not able to reproduce color or shades of grey. The process is now obsolete. It was first largely displaced by the diazo
whiteprint Whiteprint describes a document reproduction produced by using the diazo The diazo group is an organic moiety consisting of two linked nitrogen Nitrogen is the chemical element with the Symbol (chemistry), symbol N and atomic number 7. It ...
process, and later by large-format
xerographic Xerography is a dry Photocopier, photocopying technique. Originally called electrophotography, it was renamed xerography—from the Greek language, Greek Root (linguistics), roots wikt:ξηρός, ξηρός ''xeros'', "dry" and wikt:-γραφί ...
photocopiers. The term ''
blueprint A blueprint is a reproduction of a technical drawing or engineering drawing An engineering drawing is a type of technical drawing that is used to convey information about an object. A common use is to specify the geometry necessary for the co ...
'' continues to be used less formally to refer to any
floor plan In architecture File:Plan d'exécution du second étage de l'hôtel de Brionne (dessin) De Cotte 2503c – Gallica 2011 (adjusted).jpg, upright=1.45, alt=Plan d'exécution du second étage de l'hôtel de Brionne (dessin) De Cotte 2503c – Gal ...

floor plan
(and even less formally, any type of plan). Practicing engineers, architects, and drafters often call them "drawings" or "prints".


The blueprint process

The blueprint process is based on a photosensitive ferric compound. The best known is a process using ammonium ferric citrate and potassium ferricyanide. The paper is impregnated with a solution of ammonium ferric citrate and dried. When the paper is illuminated, a photoreaction turns the trivalent ferric iron into divalent ferrous iron. The image is then developed using a solution of potassium ferricyanide forming insoluble ferroferricyanide (
Prussian blue or Turnbull's blue
Prussian blue or Turnbull's blue
) with the divalent iron. Excess ammonium ferric citrate and potassium ferricyanide are then washed away. The process is also known as
cyanotype Image:Joy_Oil_gas_station_blueprints.jpg, Architectural drawing blueprint, Canada, 1936 Cyanotype is a photographic process, photographic printing process that produces a cyan, cyan-blue print. Engineers used the process well into the 20th centu ...

cyanotype
. This is a simple process for the reproduction of any light transmitting document.
Engineer Engineers, as practitioners of engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The dis ...

Engineer
s and
architect An architect is a person who plans, designs and oversees the construction of buildings. To practice architecture means to provide services in connection with the design of buildings and the space within the site surrounding the buildings that ha ...

architect
s drew their designs on
cartridge paperCartridge paper is a type of high-quality paper density, heavy paper used for illustration and drawing. The term "cartridge" refers to the history of the paper originally being used for making paper cartridges for early breechloading firearms.
; these were then traced on to
tracing paper 250px, Tracing paper roll Tracing paper is paper made to have low Opacity (optics), opacity, allowing light to pass through. It was originally developed for architects and design engineers to create drawings which could be copied precisely using ...
using
India ink India ink (British English British English (BrE) is the standard dialect of the English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, w ...
for reproduction whenever needed. 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. 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. Where
ultra-violet light Ultraviolet (UV) is a form of electromagnetic radiation In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that stud ...
is transmitted through the tracing paper, the light-sensitive coating converts to a stable blue or black dye. Where the India ink blocks the ultra-violet light the coating does not convert and remains soluble. The image can be seen forming. When a strong image is seen the frame is brought indoors to stop the process. The unconverted coating is washed away, and the paper is then dried. 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. This process has several features: Introduction of the blueprint process eliminated the expense of photolithographic reproduction or of hand-tracing of original drawings. By the later 1890s in American architectural offices, a blueprint was one-tenth the cost of a hand-traced reproduction. The blueprint process is still used for special artistic and photographic effects, on paper and fabrics. Various base materials have been used for blueprints. Paper was a common choice; for more durable prints
linen Linen () is a textile made from the fibers of the flax plant. Linen is very strong, absorbent, and dries faster than cotton. Because of these properties, linen is comfortable to wear in hot weather and is valued for use in garments. It also ha ...

linen
was sometimes used, but with time, the linen prints would shrink slightly. To combat this problem, printing on imitation vellum and, later, polyester film (
Mylar film, 32 layers of ~14 µm thickness each BoPET (biaxially-oriented polyethylene terephthalate) is a polyester Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a sp ...
) was implemented.


Whiteprints

Traditional blueprints became obsolete when less expensive printing methods and digital displays became available. In the early 1940s, cyanotype blueprint began to be supplanted by diazo prints, also known as
whiteprint Whiteprint describes a document reproduction produced by using the diazo The diazo group is an organic moiety consisting of two linked nitrogen Nitrogen is the chemical element with the Symbol (chemistry), symbol N and atomic number 7. It ...
s. This technique produces blue lines on a white background. The drawings are also called ''blue-lines'' or bluelines. Other comparable dye-based prints were known as blacklines. Diazo prints remained in use until they were replaced by
xerographic Xerography is a dry Photocopier, photocopying technique. Originally called electrophotography, it was renamed xerography—from the Greek language, Greek Root (linguistics), roots wikt:ξηρός, ξηρός ''xeros'', "dry" and wikt:-γραφί ...
print processes. Xerography is standard copy machine technology using
toner Colored toner container Toner is a powder A powder is a dry, bulk solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and conta ...

toner
on
bond paperBond paper is a high-quality durable writing paper similar to bank paper but having a Paper density, weight greater than 50 g/m2. The most common weights are 60 g/m2 (16 lb), 75 g/m2 (20 lb) and 90 g/m2 (24 lb). The name ...
. When large size xerography machines became available, 1975, they replaced the older printing methods. As
computer-aided design Computer-aided design (CAD) is the use of computers (or ) to aid in the creation, modification, analysis, or optimization of a design. This software is used to increase the productivity of the designer, improve the quality of design, improve comm ...
techniques came into use, the designs were printed directly using a
computer printer File:Printer.ogv, A video showing an Inkjet printing, inkjet printer while printing a page. In computing, a printer is a peripheral machine which makes a persistent representation of graphics or text, usually on paper. While most output is huma ...
or
plotter A plotter is a machine that produces vector graphics drawings. Plotters draw lines on paper using a pen, or in some applications, use a knife to cut a material like Polyvinyl chloride, vinyl or leather. In the latter case, they are sometimes know ...

plotter
.


Digital

In most computer-aided design of parts to be machined, paper is avoided altogether, and the finished design is an image on the computer display. The computer-aided design program generates a
computer numerical control Numerical control (also computer numerical control, and commonly called CNC) is the automated control of machining truck of the US Army with machinists working on automotive parts Machining is a process in which a material (often metal) is cut ...
sequence from the approved design. The sequence is a computer file which will control the operation of the
machine tools A machine tool is a machine for handling or machining metal or other rigid materials, usually by cutting, Boring (manufacturing), boring, grinding (abrasive cutting), grinding, shearing, or other forms of deformations. Machine tools employ some so ...
used to make the part. In the case of construction plans, such as road work or erecting a building, the supervising workers may view the "blueprints" directly on displays, rather than using printed paper sheets. These displays include mobile devices, such as
smartphone A smartphone is a portable device A mobile device (or handheld computer) is a computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern computers can perf ...

smartphone
s or tablets. Software allows users to view and annotate electronic drawing files. Many of the original paper blueprints are archived since they are still in use. In many situations their conversion to digital form is prohibitively expensive. Most buildings and roads constructed before 1990 will only have paper blueprints, not digital. These originals have significant importance to the repair and alteration of constructions still in use, e.g. bridges, buildings, sewer systems, roads, railroads, etc., and sometimes in legal matters concerning the determination of, for example, property boundaries, or who owns (and/or is responsible for) a boundary wall.


See also

* Architectural reprography *
Floor plan In architecture File:Plan d'exécution du second étage de l'hôtel de Brionne (dessin) De Cotte 2503c – Gallica 2011 (adjusted).jpg, upright=1.45, alt=Plan d'exécution du second étage de l'hôtel de Brionne (dessin) De Cotte 2503c – Gal ...

Floor plan
*
Technical drawing
Technical drawing
*
Heliographic copierA heliographic copier or heliographic duplicator is an apparatus used in the world of reprography for making contact prints on paper from original drawings made with that purpose on tracing paper, parchment paper or any other transparent or translu ...
*
Whiteprint Whiteprint describes a document reproduction produced by using the diazo The diazo group is an organic moiety consisting of two linked nitrogen Nitrogen is the chemical element with the Symbol (chemistry), symbol N and atomic number 7. It ...
*
Cyanotype Image:Joy_Oil_gas_station_blueprints.jpg, Architectural drawing blueprint, Canada, 1936 Cyanotype is a photographic process, photographic printing process that produces a cyan, cyan-blue print. Engineers used the process well into the 20th centu ...

Cyanotype


References


Further reading

* {{Visualization 1842 introductions Non-impact printing Infographics Publications by format
Technical drawing {{Commons cat, Technical drawing Architecture occupations Civil engineering Construction documents Design engineering Drawing Engineering occupations Fields of geometry Infographics Landscape architecture ...