There is something magical about watching an image bloom on paper, ghostly whites emerging against a background that shifts from a dull sage green to a brilliant Prussian blue. We had no cameras or ink, and yet we were still able to create images with little more than chemistry and sunlight.
The process is called cyanotype printing, and last Wednesday, Sept. 9, I spent an afternoon in the Olmsted Greenhouse exploring this nearly two-century-old photographic process. The workshop was led by Science Librarian Isabel Ryan and Greenhouse Manager Alicia Contelmo, who introduced us to the technique and its history. The basic idea is simple: Anything placed on the treated paper will block light and leave its silhouette behind.
We then began arranging our own compositions with fern fronds, rosemary leaves, flowers and whatever fallen materials we could find around the greenhouse. This year, the Vassar College Artifacts Project also gave us something new to experiment with by contributing early 20th-century glass lantern slides depicting geological sites such as the Grand Prismatic Spring in Yellowstone National Park.
Once we were satisfied with our arrangements, we pressed everything beneath sheets of glass to keep them in place and let them sit in the sunlight. From there, we had to trust the process.
An ideal day for cyanotypes is bright and sunny. Unfortunately, we got an almost uninterrupted cloud cover. Since cyanotypes depend on sunlight, the gray sky made the prints much fainter.
The problem becomes clearer once you understand what is actually happening to the paper. Cyanotypes use iron-based chemicals that are sensitive to ultraviolet (UV) light. Wherever UV light reaches the treated paper, it triggers a photochemical reaction that ultimately produces the insoluble dark Prussian blue color. Areas covered by leaves, flowers or other objects receive less light and remain white. Rinsing the print washes away the unreacted, water-soluble chemicals, stopping the reaction and preserving the final result.
After around 20 minutes in the dim sunlight, we looked at a few of our prints. Some emerged almost completely white, likely from underexposure. Others somehow appeared reversed, developing blue in places where we had expected white. Our first few imperfect prints only made me respect the original pioneers of the technique even more.
English polymath Sir John Herschel discovered the cyanotype process in 1842 while experimenting with light-sensitive iron salts. He initially used the process as an affordable and simple way to reproduce technical drawings, creating the very first “blueprints.”
But one of cyanotype’s most important early applications was not in engineering, but in botany. After Herschel shared this method with botanist Anna Atkins, she recognized its potential for her own work studying algae. Algae, with their branching fractal-like forms and delicate structures, were particularly difficult to reproduce accurately through illustrations. Instead, Atkins was able to use cyanotypes to preserve the scale, silhouette and intricate details of the specimens with stunning accuracy.
Beginning in 1843, she published “Photographs of British Algae: Cyanotype Impressions,” now regarded as the first photographically printed and illustrated book. Atkins is also often credited as the first female photographer.
Atkins herself explained her motivations in her book, writing that the challenge of accurately drawing such minute specimens had led her to Herschel’s “beautiful process of Cyanotype” so that she could obtain impressions of the plants themselves.
During last week’s workshop, we were able to look through a book with reproductions of Atkins’ original prints. Her work can also be found elsewhere at Vassar, as the College’s collection includes one of her original cyanotypes, “Ptelea trifoliata [Wafer ash],” dating to around 1845.
The print is currently included in the Frances Lehman Loeb Art Center’s “The Botanist at Vassar,” an exhibition organized with the Biology Department and Herbarium that examines the relationship between image-making and the scientific study of plants. The exhibition considers how images can function as both artistic illustrations and scientific tools, as well as how gender roles and technology shaped both fields. The exhibition remains open through Oct. 4.
The applications of cyanotypes in both art and science also allowed the method to endure longer than other photographic techniques developed at the same time. The daguerreotype, for example, produced highly detailed images on silver-coated copper plates and was especially popular for portraiture in the mid-19th century. However, since each plate produced a single, unique image that could not be easily reproduced, and since it was highly toxic due to its use of mercury vapor, the practice quickly fell out of fashion within just a decade.
Cyanotypes, on the other hand, were relatively inexpensive and simple to process. Beginning in the late-19th century, more architects and engineers began adopting them for blueprints. By the ’50s, newer methods had largely replaced cyanotypes for that purpose, but the medium did not entirely disappear. Contemporary photographers revived it as an alternative artistic process towards the ’00s, and artists have been using it ever since.
Back in the greenhouse, we were still faced with the pressing issue of the cloudy weather. Although a few prints were successful, the weak sunlight meant that the rest would need either much more time outside or a stronger source of UV light. Someone brought in a solution: a UV manicure lamp.
The lamp did exactly what our gray afternoon had failed to accomplish. After placing our prints beneath it and giving them a final rinse, we finally saw the rich Prussian blue we had been waiting for.
Soon, the Olmstead Greenhouse was full of prints in different stages of success, ranging from final crisp prints of ferns to washed-out silhouettes and ghostly mirages of landscapes. They were hardly perfect, but were reminiscent of Atkin’s own work. My cyanotypes are now sitting on my desk, a continuation of a process that has survived for nearly two centuries by adapting continuously to new purposes and technologies. It feels fitting that ours came to life with a particularly modern addition—the nail lamp.