Blue-prints and White-prints or blue-lines

June 2017
These days we are working on a few blue-prints and blue-lines in our lab. Before starting the work, we tried to discuss the material and technique used in making them. This write-up is the summary of our discussion on the topic.

Both these processes (blue prints and blue lines/white prints) use different light sensitive chemicals for re-producing or copying the original drawings made on translucent paper. These processes were discontinued over a period of time because more stable and easier processes  were developed later to replace them.

Here we will share some information regarding these two techniques.


A blueprint is a type of paper-based reproduction usually of a technical drawing, documenting architecture or engineering designs. 




John Herschel, who was a chemist, astronomer, and photographer, developed the process for blueprints in 1842. Herschel had discovered the cyanotype process after a series of experiments. The process starts by taking a drawn image on semi-transparent paper weighed down on top of a sheet of paper or cloth. The paper or cloth is pre-coated with a photosensitive chemical mixture of potassium ferricyanide and ferric ammonium citrate. Once the drawing is exposed to light the exposed parts of the drawing (the background) became blue, while the drawing lines blocked the coated paper from exposure and remained white.

Introduction of the blueprint process eliminated the expense of photo lithographic reproduction and the need to hand-trace original drawings.

White-prints or Blue-lines  IMG_0411

Whiteprint describes a document reproduction produced by using the diazo chemical process. It is also known as the blue-line process since the result is blue lines on a white background. It is a contact printing process which accurately reproduces the original in size, but cannot reproduce continuous tones or colors. The light-sensitivity of the chemicals used was known in the 1890s and several related printing processes were patented at that time. Whiteprinting replaced the blueprint process for reproducing architectural and engineering drawings because the process was simpler and involved fewer toxic chemicals. A blue-line print is not permanent and will fade if exposed to light for weeks or months, but a drawing print that lasts only a few months is sufficient for many purposes.


There are two components in this process:

  1. diazonium salt: a light sensitive chemical
  2. Azo dye (also known as the coupler): a colorless chemical that combines with the salt to produce color.
Author: namitajaspal
Namita Jaspal, with inherited skills of art and aesthetics and passion for science, opted to pursue post- graduation in ‘Conservation of Cultural Property’ after her graduation in Science from Delhi University in 1992. Four year intense training at National Museum Institute provided the right foundation to start a career in Conservation. She is currently practicing conservation consultancy for Heritage property including monuments and collections. She has been doing independent research in conservation techniques and procedures in Indian context. She is currently working on the conservation of wall-paintings of Sri Harmandir Sahib Ji (The Golden temple at Amritsar. The project is nearing completion and getting a lot of appreciation for the organized and ethical treatment it is providing. It is for the first time in the history of Sri Harmandir Sahib Ji (The Golden Temple) that wall painting conservation and preservation is being done in a scientific manner, keeping the codes of Ethics into consideration while decision making. Another project just completed is of the Conservation of Krishna Temple at Kishankot, Gurdaspur, Punjab. In her private Conservation Laboratory, she is not only providing onservation services, but also mentoring young aspiring conservators and archaeologists by the way of training and paid internships. She has been a guest lecturer at DIHRM (Delhi Institute of Heritage Research and Management). With all the updated knowledge database and innovative practical approaches relevant to the Indian conditions, she could successfully do curative and preservative treatment of very old textiles like a nine feet long flag from nineteenth century that is regarded as priceless memorabilia of second Dogra regiment at Chandi Mandir, and four hundred years old (seventeenth century) Chola Sahib Ji of Sixth Guru of Sikhs, Sri Hargobind Sahib Ji. Apart from this she has done conservation of Photograph collections, archival records, numerous paintings, manuscripts and other cultural objects. She is also involved in preparation of up-gradation proposals for museums and such organizations. Her expertise includes Conservation and preservation technologies and procedures for conservation of varied material like wall paintings, paper, photographs, textile, ceramics, stone, metal and archaeological objects.

1 thought on “Blue-prints and White-prints or blue-lines

  1. Just wanted to thank you for the article explaining the differences between blueprints & blue line prints. As a drafter, I’ve made my share of blue lines over the years, but remember seeing blueprints as a child. In my current job, I’m finding some very old blueprints in the archives. Now that most drafting is done with CAD, we can just have the plotter spit out another copy.

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