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From blue skies to blue print: Astronomer John Herschel’s invention of the cyanotype

For Sir John Herschel, science and art were inextricably linked. Son of the celebrated astronomer William Herschel—who, with the discovery of the planet Uranus, revolutionized the modern day conception of the universe—science was in John Herschel’s blood. Following in his father’s footsteps, Herschel himself became a renowned astronomer. Herschel also applied scientific exploration to art and participated in some of photography’s earliest experimentation.

An accomplished chemist, Herschel discovered the action of hyposulfite of soda on silver salts, which lead to the use of “hypo” as the most effective fixing agent for silver-based photography. Herschel also endorsed and encouraged the term “photography” and coined the terms “negative” and “positive” to refer to photographic images.

John Herschel not only searched the dark blue skies, but also searched for ways to introduce color into photography. A child of Newtonian science, Herschel knew that white light is composed of the color spectrum. The trick was to separate the white light and pinpoint specific colors: “By using the prism first to separate all but the pure prismatic tint of given refrangibility and then re-analyzing this by media I conceive it possible to obtain rays totally exempt from any colour but the elementary one wanted” Herschel theorized in a letter, dated July 6, 1839, to Henry F. Talbot, another scientist interested in experimental photography.

During his quest for color, Herschel carefully documented his experiments with hundreds of variations of chemical formulas, using engravings as source imagery to create negatives on paper. In 1842, Herschel invented the cyanotype.

The cyanotype process uses light-sensitive iron salts produced by brushing solutions of ferric ammonium citrate and potassium ferricyanide, also known as Prussian blue, onto paper, which is then dried in the dark. Cyanotypes were not widely used until 1880, when they became popular because they required only water for fixing the image.

The cyanotype is one of Herschel’s most influential contributions to the art of photography. Not only does it lend itself to strikingly beautiful photos, but the cyanotype is also the originator of the architect blue-print.

One of Herschel’s cyanotypes is featured in the exhibition Discovering the Language of Photography: The Gernsheim Collection. Closing in just a few weeks, the exhibition can be seen in the Ransom Center Galleries on Tuesdays through Fridays from 10 a.m. to 5 p.m., with extended Thursday hours until 7 p.m. On Saturdays and Sundays the galleries are open from noon to 5 p.m. The galleries are closed on Mondays. Free docent-led tours of the Gernsheim exhibition are offered at 2 p.m. on this Saturday and Sunday.

Please click on the thumbnails below to view full-size images.

Darwin and Herschel: The Fossil Record of a Relationship

2009 marks the bicentennial of Charles Darwin’s birth and the 150th anniversary of the publication of his most famous work, On the Origin of Species. The Ransom Center owns several copies of the first edition, the most interesting being the one sent by Darwin to Sir John Herschel, a famous English scientist of his day, inscribed simply “From the author.”

Darwin identified Herschel in the second sentence of the Origin as “one of our greatest philosophers.” Early in his career, Darwin knew that the elder scientist had defined “the species question”—or in Herschel’s words, “that mystery of mysteries” —as being the central one for the new science of biology (the term wasn’t widely used until mid-century). In 1836, the young scientist, then only 25, was returning from his famous voyage to the Galapagos Islands on board the Beagle.

From June 8 to 15, 1836, the Beagle was in port at Cape Town, and during this time Darwin visited Herschel, who had established an observatory in South Africa in order to expand the star catalogs made by his father, William Herschel.

We don’t know what was said, but very likely geology and volcanology were involved. Herschel inspired Darwin to apply the critical analysis of data associated with the physical sciences to the emerging life sciences. As University of Texas at Austin Professor Steven Weinberg recently noted in a talk at the Ransom Center, astronomy has historically led the way in the development of scientific methodology, later applied to other disciplines.

The Darwin-Herschel copy of the Origin, along with the letter of transmittal, stands behind as the “fossil record” of this remarkable meeting. The text of Darwin’s letter follows:

Down Bromley Kent
Nov. 11th. [1859]

My dear Sir John Herschel

I have taken the liberty of directing Murray [John Murray, his publisher] to send you a copy of my book on the Origin of species, with the hope that you may still retain some interest on this question.— I know that I ought to apologise for troubling you with the volume & with this note (which requires no acknowledgment) but I cannot resist the temptation of showing in this feeble manner my respect, & the deep obligation, which I owe to your Introduction to Natural Philosophy. Scarcely anything in my life made so deep an impression on me: it made me wish to try to add my mite to the accumulated store of natural knowledge

With much respect | I beg leave to remain | Yours sincerely | Charles Darwin

The copy of the Origin volume mentioned in this blog is on display in the Ransom Center Reading Room lobby from November 19 through January 15, 2010, during Reading Room hours.