# Blueprint
A blueprint is a contact print of a technical drawing made by the cyanotype photographic process, in which white lines appear on a Prussian-blue ground. The term also names the drawings themselves and, by extension since the 1920s, any detailed plan of action.[1](https://www.etymonline.com/word/blueprint) • [2](https://www.oxfordlearnersdictionaries.co.uk/definition/english/blueprint)
| Key fact | Detail |
|---|---|
| Invention | The cyanotype process was invented by Sir John Herschel in the summer of 1842; one museum source dates it to 1841[3](https://www.si.edu/object/photographic-history-collection-cyanotypes%3Anmah_1343353) • [4](https://blog.scienceandmediamuseum.org.uk/introduction-cyanotype-process/) |
| Chemistry | Paper coated with ferric ammonium citrate and potassium ferricyanide; ultraviolet light produces the insoluble blue dye Prussian blue, and washing in water fixes the image[5](https://hnoc.org/virtual-exhibitions/from_daguerreotype_to_digital/cyanotype-process) |
| Image form | A negative print: the drawing's inked lines block the light, so the copy shows white lines on a blue background[6](https://nbm.org/adopt-an-artifact-blueprint-machine/) |
| First book use | Anna Atkins's *Photographs of British Algae: Cyanotype Impressions* (1843) is the earliest-known photographically illustrated book, using cyanotypes for both images and text[5](https://hnoc.org/virtual-exhibitions/from_daguerreotype_to_digital/cyanotype-process) |
| Commercial takeoff | Blueprint paper was marketed from the 1870s, notably by the Paris firm Marion & Co.; most surviving blueprints date from the 1870s to the 1930s[3](https://www.si.edu/object/photographic-history-collection-cyanotypes%3Anmah_1343353) • [7](https://psap.library.illinois.edu/collection-id-guide/archdrawingrepro) |
| Decline | Diazo ("whiteprint") copiers almost completely replaced blueprints in the 1940s, and xerographic photocopiers replaced the diazo process in the 1970s[6](https://nbm.org/adopt-an-artifact-blueprint-machine/) |
| Figurative word | "Blueprint" as a noun is attested from 1882, the figurative sense "detailed plan" from 1926, and the verb from 1939[1](https://www.etymonline.com/word/blueprint) |
## The cyanotype process
The cyanotype is an iron-based photographic process rather than a silver-based one. Paper is coated with a solution of ferric ammonium citrate and [potassium ferricyanide](https://www.edgepedia.org/potassium-ferricyanide) and dried in the dark, because the salts are sensitive to ultraviolet light.[5](https://hnoc.org/virtual-exhibitions/from_daguerreotype_to_digital/cyanotype-process) A translucent original, or an object such as a plant, is laid directly against the coated paper and the two are exposed together to sunlight or an ultraviolet lamp. Where light strikes, the iron salts are reduced and react to form [Prussian blue](https://www.edgepedia.org/prussian-blue), an insoluble dye; where the drawing's ink blocks the light, the salts remain and are washed away in plain water, leaving white lines on the blue ground.[5](https://hnoc.org/virtual-exhibitions/from_daguerreotype_to_digital/cyanotype-process) • [6](https://nbm.org/adopt-an-artifact-blueprint-machine/)
Because the process has a low sensitivity to light, contact printing is the practical method, and exposures are long. Anna Atkins exposed her specimens for between 10 and 40 minutes in daylight.[3](https://www.si.edu/object/photographic-history-collection-cyanotypes%3Anmah_1343353) • [8](https://www.nhm.ac.uk/discover/anna-atkins-cyanotypes-the-first-book-of-photographs.html) Processing is simple: the unexposed sensitizer and reaction products are water-soluble, so washing completes the print, and no darkroom is required.[3](https://www.si.edu/object/photographic-history-collection-cyanotypes%3Anmah_1343353) The result is a stable image, and the process was cheaper and simpler than silver gelatin printing, which made it attractive for large-volume copying.[3](https://www.si.edu/object/photographic-history-collection-cyanotypes%3Anmah_1343353) • [9](https://www.ocemuseum.nl/blueprint/?lang=en)
## Anna Atkins and the first photographic book
Within a year of Herschel's invention, the botanist and photographer Anna Atkins (1799–1871) used the process to make *[Photographs of British Algae: Cyanotype Impressions](https://www.edgepedia.org/photographs-of-british-algae-cyanotype-impressions)* (1843), the earliest-known photographically illustrated book, with cyanotypes serving for the images and the text pages alike.[5](https://hnoc.org/virtual-exhibitions/from_daguerreotype_to_digital/cyanotype-process) The text pages and captions were photographic facsimiles of her handwriting, and in some cases the lettering was formed from strands of seaweed.[8](https://www.nhm.ac.uk/discover/anna-atkins-cyanotypes-the-first-book-of-photographs.html) She made every print herself, and the volumes held by the Natural History Museum contain 411 plates each, with scientific names written in by hand.[8](https://www.nhm.ac.uk/discover/anna-atkins-cyanotypes-the-first-book-of-photographs.html) About 20 copies of the book are known, 15 of them substantially complete.[8](https://www.nhm.ac.uk/discover/anna-atkins-cyanotypes-the-first-book-of-photographs.html) She continued to use the process through the 1850s, including for her 1853 *Cyanotypes of British and Foreign Ferns*.[4](https://blog.scienceandmediamuseum.org.uk/introduction-cyanotype-process/)
## Adoption in architecture and engineering
The process did not spread immediately. Herschel's prepared paper kept for only a few weeks unexposed, and the cyanotype was used mainly by amateur photographers in its first decades.[9](https://www.ocemuseum.nl/blueprint/?lang=en) • [10](https://nieuweinstituut.nl/en/projects/invented-from-copies/de-introductie-van-de-blauwdruk-de-architectonische-ontwerppraktijk) From 1870, German, Austrian, and French manufacturers succeeded in extending the paper's shelf life, and by the end of the nineteenth century it kept for a year. This made commercial blueprint paper practical, and the Paris company Marion & Co. began marketing what is now recognized as blueprint paper in the 1870s.[3](https://www.si.edu/object/photographic-history-collection-cyanotypes%3Anmah_1343353) • [9](https://www.ocemuseum.nl/blueprint/?lang=en)
For architects and engineers the process solved a specific problem: before photomechanical copying, every copy of a drawing had to be traced by hand, line by line, a slow and error-prone task known as calquering.[9](https://www.ocemuseum.nl/blueprint/?lang=en) • [10](https://nieuweinstituut.nl/en/projects/invented-from-copies/de-introductie-van-de-blauwdruk-de-architectonische-ontwerppraktijk) A blueprint instead produced a high-fidelity, scale-accurate copy from a translucent original drawn in black ink on tracing paper or linen. The original and the sensitized sheet were clamped together in a printing frame, or wrapped around a glass cylinder, and exposed to sunlight or ultraviolet light; the ink blocked the light and the copy emerged as white lines on blue.[6](https://nbm.org/adopt-an-artifact-blueprint-machine/) • [10](https://nieuweinstituut.nl/en/projects/invented-from-copies/de-introductie-van-de-blauwdruk-de-architectonische-ontwerppraktijk) Demand grew with industrialization, larger architectural offices, and municipal permit rules that required precise copies of building plans; in the Netherlands, for example, building plans had to be approved by the municipality from 1872.[10](https://nieuweinstituut.nl/en/projects/invented-from-copies/de-introductie-van-de-blauwdruk-de-architectonische-ontwerppraktijk)
Dedicated machinery followed. A 1910 blueprint machine made by the C.F. Pease Company of Chicago, now in the National Building Museum, clamps the original and the sensitized sheet to a large glass cylinder while a lamp inside exposes the paper.[6](https://nbm.org/adopt-an-artifact-blueprint-machine/) An electric printer introduced in 1903 reduced the time for a print to about 10 minutes, and one Dutch firm advertised a machine capable of a 5 m² print.[10](https://nieuweinstituut.nl/en/projects/invented-from-copies/de-introductie-van-de-blauwdruk-de-architectonische-ontwerppraktijk) Users included shipbuilding, machine building, electrical engineering, and construction, and the prints also served for correcting designs: on surviving industrial blueprints, changes were marked in red lines over the cyanotype after printing.[9](https://www.ocemuseum.nl/blueprint/?lang=en) • [11](https://blog.cmog.org/2018/best-laid-plans-how-sketches-and-blueprints-inform-design-process)
## Decline and successors
Blueprinting remained a standard technique for reproducing technical drawings well into the 1940s, but it had drawbacks: the wet washing step was difficult with large sheets, and the chemicals were hazardous and pungent.[6](https://nbm.org/adopt-an-artifact-blueprint-machine/) • [9](https://www.ocemuseum.nl/blueprint/?lang=en) Diazonium ("whiteprint") copiers, which produce a direct positive with dark lines on a white background and develop by ammonia vapor rather than washing, almost completely replaced the blueprint in the 1940s.[6](https://nbm.org/adopt-an-artifact-blueprint-machine/) • [12](https://files.eric.ed.gov/fulltext/ED219653.pdf) The diazo process was itself replaced in the 1970s by xerographic photocopiers, which remain standard.[6](https://nbm.org/adopt-an-artifact-blueprint-machine/)
The word outlived the process. The figurative sense, a complete plan for achieving something, is attested from 1926 and is now common in political and business language, as in "a blueprint for reform."[1](https://www.etymonline.com/word/blueprint) • [2](https://www.oxfordlearnersdictionaries.co.uk/definition/english/blueprint) The cyanotype itself survives as an artistic and photographic process, and the white-on-blue look remains a recognizable visual motif in design.[10](https://nieuweinstituut.nl/en/projects/invented-from-copies/de-introductie-van-de-blauwdruk-de-architectonische-ontwerppraktijk)
## References
1. [Blueprint (n.), Etymonline](https://www.etymonline.com/word/blueprint)
2. [blueprint noun, Oxford Advanced Learner's Dictionary](https://www.oxfordlearnersdictionaries.co.uk/definition/english/blueprint)
3. [Photographic History Collection: Cyanotypes, Smithsonian National Museum of American History](https://www.si.edu/object/photographic-history-collection-cyanotypes%3Anmah_1343353)
4. [Introduction to the cyanotype process, National Science and Media Museum](https://blog.scienceandmediamuseum.org.uk/introduction-cyanotype-process/)
5. [Cyanotype Process: 1842–today, The Historic New Orleans Collection](https://hnoc.org/virtual-exhibitions/from_daguerreotype_to_digital/cyanotype-process)
6. [Adopt an Artifact: Blueprint Machine, National Building Museum](https://nbm.org/adopt-an-artifact-blueprint-machine/)
7. [Architectural Drawing Reproduction, Preservation Self-Assessment Program, University of Illinois](https://psap.library.illinois.edu/collection-id-guide/archdrawingrepro)
8. [Anna Atkins's cyanotypes: The first book of photographs, Natural History Museum, London](https://www.nhm.ac.uk/discover/anna-atkins-cyanotypes-the-first-book-of-photographs.html)
9. [Blueprint, Océ Museum](https://www.ocemuseum.nl/blueprint/?lang=en)
10. [How the Blueprint Entered Architectural Design, Het Nieuwe Instituut](https://nieuweinstituut.nl/en/projects/invented-from-copies/de-introductie-van-de-blauwdruk-de-architectonische-ontwerppraktijk)
11. [How sketches and blueprints inform the design process, Corning Museum of Glass](https://blog.cmog.org/2018/best-laid-plans-how-sketches-and-blueprints-inform-design-process)
12. [Reproduction processes for drawings (diazo dry print process), ERIC document ED219653](https://files.eric.ed.gov/fulltext/ED219653.pdf)
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*Topic: Encyclopedia › Technology and the built world › Communications and everyday technology › Printing and typography › Printing processes and techniques*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 15, 2026 · Edited: Sep 30, 2026; Oct 15, 2026 · Last review: Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license