Why Are Blueprints Blue?

The traditional color of blueprints wasn't chosen because it's pretty -- it's a result of a chemical copying process. Learn the history of blueprints in this episode of BrainStuff.

Learn more about your ad-choices at https://www.iheartpodcastnetwork.com

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff,
Lauren vocal bomb here. If you have a blueprint for success,
you're not alone, at least when it comes to the
blueprint part. The word blueprint has become part of a
global lexicon used to symbolize a plan, strategy, or framework.
But what is a blueprint really? At its most basic,

(00:23):
a blueprint is a reproduction of an image that already exists.
Engineers or architects use these large format prints to illustrate
project plans, using white lines and text on a backdrop
of blue. And it's not just because they happen to
like the color. A blueprint signature hue is tied to
a chemical process. In eighteen forty two, an English photographer, chemist,

(00:44):
and astronomer named John Herschel discovered the combining ferric ammonium
citrate and potassium fair cyanide created a chemical reaction and
a compound called blue ferric fair sydanide or Prussian blue.
This photosensitive solution could be used to reproduces documents in
a process similar to developing a photograph from a negative.

(01:05):
The process, called cyana type, was adopted by early photographers
and led to the first book illustrated by photography, and
then became the darling of architects and engineers. Here's how
it works. First, you create a drawing, then transfer it
to vellum paper or tracing cloth, both of which are
so thin that light can pass through them. Then you

(01:25):
saturate a piece of regular paper with an ammonium potassium
mixture and let it dry. Place the transparent vellum or
tracing cloth with the drawing atop the paper coated in
the chemical solution, Shine a bright light down through the drawing,
and wait for the chemical reaction to take place. Within
a matter of minutes, the chemical coated paper will be
transformed into blue ferric fairr cyanide, with one important exception,

(01:49):
wherever the light can't shine through the top paper because
of the lines from the drawing, the blue printing paper
remains white. After rinsing the paper in cold water to
halt the chemical action and allowing the paper to dry
in the dark, you're left with a nearly identical duplicate
of the original drawing, just the lines are white and
the background is dark, where the lines were originally dark

(02:10):
and the background was light. Although this process requires several steps,
it became a big hit with the pre computer crowd
of the nineteen and twenty centuries, as it was still
faster and cheaper than creating large scale drawings by hand.
The story of the creation of Prussian blue has all
the elements of a dark fairy tale. In seventeen o four,
an alchemist and a dye maker shared a laboratory in Berlin, Germany.

(02:32):
The former, Johann Konrad Dipple, sought to create a universal remedy,
one that treated everything from animal mange to human epilepsy
by boiling hoofs, horns, and leather into a smelly elixir.
The ladder, a fellow named Teese Box made batches of
vibrant dyes. One day, as these, Box simmered insects, alum,
iron and sulfate to create a deep red, he borrowed

(02:54):
some potash to the alchemist and added it to his
viscous mixture. This horrible brew created a blue as deep
as the night sky. After retracing the steps in the process,
Dipple realized the potash contained ox blood that, when mixed
with iron sulfate, caused a chemical reaction and turned a
brilliant shade of blue. Unlike other blue dyes that were

(03:15):
difficult to make and easily faded. This blue remained vivid,
and it was inexpensive. Other blue dyes of the time
required ingredients like lapis lazili, which at the time cost
more than gold. Initially, Dipple called the color Berlin blue
as a nod to his city of residents. Later it
was called Prussian blue because it was used to dye

(03:35):
uniform fabric for the Prussian Army. The color became both
the symbol of aggression and a term of endearment because
of the army's fierce battles and serendipitous interventions and conflicts
like the Battle of Waterloo. By the late eighteen hundreds,
Prussian blue had found favor with impressionist artists and Japanese printmakers.
As the nineteen hundreds wore on, it became the hue

(03:56):
of newspaper inc typewriter ribbon, and eyeshadow. Scientists even discovered
Prussian blue works as an antidote to heavy metal poisoning
by acting as a magnet to attract and evacuate heavy
metals from the bloodstream. Eventually, Prussian blue became as important
for its practicality as its novelty. But not While John
Herschel was alive to see it. It wasn't until five

(04:18):
years after his death that blueprints were recognized as an
inexpensive and simple way to reproduce architectural drawings. By the
nineteen seventies, the blue printing process was a dying art
in the United States because new technology was becoming more prevalent.
Zerographic copies could create duplicates with the push of a button,
and by the nine eighties the architecture, engineering, and construction

(04:39):
industries were making the move from hand drawing to computer
aided design that could be printed on large scale paper. Today,
blueprints aren't usually blue. They're most often black or gray
lines on a white background. Today's episode was written by
Laurel Dove and produced by a Playing Brain. Stuff is

(05:01):
a production of I Heart Radio's How Stuff Works. For
more on this and mons of other original topics, visit
our home planet, how stuff Works dot com. And for
more podcasts from my heart Radio, visit i heart Radio app,
Apple Podcasts, or wherever you listen to your favorite shows.