View source for Blueprint

{{Short description|Document reproduction by contact printing on light-sensitive sheets}}
{{other uses}}
[[File:John C. Butler-class destroyer escort outboard profile, 29 September 1944 (20737474).JPG|thumb|Blueprint for a [[John C. Butler-class destroyer escort|''Butler''-class destroyer escort]], 1944]]{{Technical drawings|expanded=Types}}
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.<ref name="EncycBrit">{{cite book |last1=Go. |first1=F. E. |chapter=Blueprint|title=Encyclopædia Britannica |date=1970 |volume= 3|publisher=William Benton, Encyclopædia Britannica Inc. |location=Chicago |isbn=0-85229-135-3 |page=816 |edition=Expo'70 |language=en}}</ref> The traditional white-on-blue appearance of blueprints is a result of the [[cyanotype]] process, which allowed rapid and accurate production of an unlimited number of copies of an original reference. It was widely used for over a century for the reproduction of specification drawings used in [[Architectural drawing#Working drawings|construction]] and industry. Blueprints were characterized by white lines on a blue background, a [[Negative (photography)|negative]] of the original. Color or shades of grey could not be reproduced.

The process is obsolete, initially superseded by the [[whiteprint#The_diazo_printing_process|diazo-based ''whiteprint'']] process, and later by large-format [[xerography|xerographic]] photocopiers. It has since almost entirely been superseded by digital computer-aided construction drawings.

The term ''[[wikt:blueprint|blueprint]]'' continues to be used informally to refer to any [[floor plan]]<ref>{{ShorterOxfordEnglishDictionary}}</ref> (and by analogy, [[wikt:blueprint|any type of plan]]).<ref>{{cite web |url=http://dictionary.reference.com/browse/blueprint?s=t |title=Blueprint |work=Dictionary.com |access-date=February 6, 2016}}</ref><ref>{{cite web |url=https://www.merriam-webster.com/dictionary/blueprint |title=Blueprint |work=Merriam-Webster Dictionary |access-date=February 6, 2016}}</ref> Practising engineers, architects, and drafters often call them "drawings", "prints", or "plans".<ref>{{cite book |last1= C. Brown|first1= Walter|last2= K. Brown|first2= Ryan |date= 2011|title=Print Reading for Industry, 10th edition |publisher= The Goodheart-Wilcox Company, Inc.|page= 4|isbn=978-1-63126-051-3}}</ref>

==The blueprint process==
[[File:The Women's Royal Naval Service on the Home Front, 1917-1918 Q19716.jpg|thumb|A member of the [[Women's Royal Naval Service]] operates a blueprinting machine during World War&nbsp;I]]
[[File:Waldhaus Gasterntal Plan5.JPG|right|thumb|Architectural drawing, Germany, 1902]]
[[File:Joy Oil gas station blueprints.jpg|right|thumb|Architectural drawing, Canada, 1936]]

The blueprint process is based on a [[Photosensitivity|photosensitive]] ferric compound. The best known is a process using [[ammonium ferric citrate]] and [[potassium ferricyanide]].<ref>{{Citation | url = http://www.pslc.ws/macrog/work/blue.htm | title = Blue | publisher = PSLC | place = WS}}.</ref><ref>{{cite book |last1= C. Brown|first1= Walter|last2= K. Brown|first2= Ryan |date= 2011|title=Print Reading for Industry, 10th edition |publisher= The Goodheart-Wilcox Company, Inc.|page= 7|isbn=978-1-63126-051-3}}</ref> 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|Prussian blue or Turnbull's blue]]) with the divalent iron. Excess ammonium ferric citrate and potassium ferricyanide are then washed away.<ref name="columbia">{{cite book |editor1-last=Bridgwater |editor1-first=William |editor2-last=Sherwood |editor2-first=Elizabeth J. |title=The Columbia Encyclopedia in One Volume |date=1950 |publisher=Columbia University Press |location=Morningside Heights, New York City |page=214 |edition=Second |language=en |type=hardbound |chapter=blueprint}}</ref> The process is also known as [[cyanotype]].

This is a simple process for the reproduction of any light transmitting document. [[Engineer]]s and [[architect]]s drew their designs on [[cartridge paper]]; these were then traced on to [[tracing paper]] using [[India ink]] 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 thirty minutes under an overcast sky to complete the exposure. Where [[ultra-violet light]] 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:<ref>Ralph W. Liebing ''Architectural Working Drawings'', John Wiley & Sons, 1999 {{ISBN|0471348767}} page 576</ref>{{bulleted list |the image is stable|as it is a contact process, no large-field optical system is required|the reproduced document will have the same [[Scale (ratio)|scale]] as the original|the paper is soaked in liquid during processing, and minor distortions can occur|the dark blue background makes it difficult to alter, thus preserving{{bulleted list|the approved drawing during use|a record of the approved specifications|the history of alterations recorded on the sheet|the references to other drawings}}}}

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.<ref>Mary N. Woods ''From Craft to Profession: The Practice of Architecture in Nineteenth-Century America'' University of California Press, 1999 {{ISBN|0520214943}}, pages 239–240</ref> The blueprint process is still used for special artistic and photographic effects, on paper and fabrics.<ref>Gary Fabbri, Malin Fabbri ''Blueprint to Cyanotypes – Exploring a Historical Alternative Photographic Process'' Lulu.com, 2006 {{ISBN|141169838X}} page 7{{self-published source|date=February 2020}}</ref>{{self-published inline|date=February 2020}}

Various base materials have been used for blueprints.  Paper was a common choice; for more durable prints [[linen]] was sometimes used, but with time, the linen prints would shrink slightly.  To combat this problem, printing on [[vellum#Paper vellum|imitation vellum]] and, later, polyester film ([[Mylar]]) was implemented.

==Whiteprints==
[[File:Heliographic_copy.jpg|thumb|[[Whiteprint]] plan copy]]

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 [[whiteprint#The_diazo_printing_process|diazo prints]], also known as [[whiteprint]]s. This technique produces blue lines on a white background. The drawings are also called ''blue-lines'' or bluelines.<ref>{{Ullmann |doi=10.1002/14356007.o13_o08.pub2|title=Imaging Technology, 2. Copying and Nonimpact Printing Processes|last1=Pai|first1=Damodar M.|last2=Melnyk|first2=Andrew R.|last3=Weiss|first3=David S.|last4=Hann|first4=Richard|last5=Crooks|first5=Walter|last6=Pennington|first6=Keith S.|last7=Lee|first7=Francis C.|last8=Jaeger|first8=C. Wayne|last9=Titterington|first9=Don R.|last10=Lutz|first10=Walter|last11=Bräuninger|first11=Arno|last12=De Brabandere|first12=Luc|last13=Claes|first13=Frans|last14=De Keyzer|first14=Rene|last15=Janssens|first15=Wilhelmus|last16=Potts|first16=Rod|pages=1–53|isbn=9783527306732}}</ref><ref>
[https://www.britannica.com/EBchecked/topic/642801/whiteprint Blueprints replaced by whiteprints]</ref> Other comparable dye-based prints were known as blacklines. Diazo prints remained in use until they were replaced by [[Xerography|xerographic]] print processes.

Xerography is standard copy machine technology using [[toner (printing)|toner]] on [[copy paper]]. When large size xerography machines became available, {{circa}} 1975, they replaced the older printing methods. As [[computer-aided design]] techniques came into use, the designs were printed directly using a [[computer printer]] or [[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]] sequence from the approved design. The sequence is a computer file which will control the operation of the [[machine tools]] 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]]s or [[Tablet computer|tablet]]s.<ref>{{cite web|last=Singer|first=Michael|title=Crain Construction grows its 80-year-old business with iOS, Android tablets|url=http://tabtimes.com/case-studies/mobile-workers/2013/03/25/crain-construction-grows-its-80-year-old-business-ios-android|publisher=tabtimes.com|access-date=21 May 2014|url-status=dead|archive-url=https://web.archive.org/web/20140522014354/http://tabtimes.com/case-studies/mobile-workers/2013/03/25/crain-construction-grows-its-80-year-old-business-ios-android|archive-date=22 May 2014}}</ref> Software allows users to view and annotate electronic drawing files. Construction crews use software in the field to edit, share, and view blueprint documents in real-time.<ref name="HCSS-blueprints">{{cite web |title=Construction Blueprint App |date=15 December 2021 |url=https://www.hcss.com/products/field-blueprint-app/ |website=HCSS |access-date=9 June 2022}}</ref>

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 {{circa}} 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 or is responsible for a boundary wall.

==See also==
*[[Architectural reprography]]
*[[Cyanotype]]<!-- refs rescued from iron(III) chloride: Historically it was used to make direct positive [[blueprint]]s.<ref>{{Cite patent|country=US|number=241713|title=Method of preparing paper|status=Patent|pubdate=1881|invent1=Pellet H}}</ref><ref>{{Cite book|url=https://archive.org/details/modernheliograph00liet|title=Modern Heliographic Processes|vauthors=Lietze E|publisher=D. Van Norstrand Company|year=1888|location=New York|pages=[https://archive.org/details/modernheliograph00liet/page/65 65]}}</ref>-->
*[[Floor plan]]
*[[Graph paper]]
*[[Heliographic copier]]
*[[Print reading]]
*[[Technical drawing]]
*[[Whiteprint]]

==References==
{{Reflist}}

==Further reading==
*{{Wiktionary-inline}}
*{{Commons category-inline}}
{{Refbegin}}
*{{cite journal |date=November 1915  |title=Man And His Machines: Electric Blue Printing Machine |journal=[[World's Work|The World's Work: A History of Our Time]] |volume= XXXI | page = 113 |last1 = Page |first1 = Walter Hines |last2 = Page |first2 = Arthur Wilson }}
{{Refend}}

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[[Category:1842 introductions]]
[[Category:Non-impact printing]]
[[Category:Infographics]]
[[Category:Printing technology]]
[[Category:Publications by format]]
[[Category:Technical drawing]]