What a Chart of Urine Tells Us About the History of Color Printing

In the early 16th century, books did not include images unless there was a very good reason. “To print images in books at the time required planning, time, and extra money,” says Caroline Duroselle-Melish, a curator at the Folger Shakespeare Library. “They were not simply decorative. An image was a real investment.”

The full-page, color spread (above) in Ulrich Pinder’s medical text, Epiphanie medicorum, printed in 1506 in Nuremberg, Germany, must have seemed crucial to his project. On the left-hand page is a wheel of flasks, each colored a different shade of yellow, pink, black, brown, or greenish blue. Opposite, the same flasks are arranged in rows, with more detail about the colors and what each shade might mean. All the flasks were meant to represent samples of human urine.

At the time, urinalysis had already been practiced for hundreds of years and was on the verge of becoming so popular that people started self-diagnosing their ailments based on the color of their pee. This revolution in home medicine depended in part on printing technology that created access to information once restricted to the medical professionals of the time.

But printing technology was not yet good enough that images could be counted on to reliably convey what they were meant to. “This is a case where you really should read and not only look at the image,” says Duroselle-Melish, who curated the Folger’s new exhibition, Beyond Words: Book Illustration in the Age of Shakespeare, which features Pinder’s book alongside more than 80 other illustrated books and prints from the 15th to 18th centuries.

As far back as 100 B.C., Sanskrit medical texts from South Asia described 20 different types of urine and the ailments they might indicate. In ancient Greece, Hippocrates hypothesized that urine represents a filtrate of the four humors, the balance of which determines a person’s health. He believed it came from the blood and was filtered through the kidneys. As an article in Kidney International notes, this was “a fairly accurate description.”

Although not all of the early work using urine as a diagnostic tool holds up, ancient physicians knew that sweet-tasting urine (a sign of diabetes) or cloudy urine (indicating dehydration, infection, or a host of other things) were causes for concern. By the Roman era, the physician Galen improved on Hippocrates’s analysis, correctly postulating that urine was a filtrate of the blood.

Most diagnoses were made by inspecting urine visually. But physicians also tasted samples, and one influential seventh-century scientist developed a test that used heat to precipitate proteins from urine to provide more information. Urinalysis, according to the Journal of the Royal College of Physicians of Edinburgh, can be considered “the first laboratory test documented in the history of medicine.”

During the Middle Ages, the popularity of urinalysis increased, and it became a primary tool for health assessment. One 12th-century physician invented a special glass vessel used to collect and examine urine samples. Every respectable physician had one, and they became a symbol of the profession.

Soon experts started publishing urine charts as teaching tools. When books were printed in Latin, the secrets of urine stayed within the medical profession, but starting around the time Pinder’s book was published these charts began to be translated out of Latin, which gave more people access to them. Soon, healers with no medical training were offering to diagnose ailments based on pee color alone. By the 17th century, these “pisse prophets” had become so ubiquitous that one writer, Thomas Brian, published a takedown of the whole profession.

While visual urinalysis is a legitimate diagnostic tool, it was a problem how much the medical profession had come to rely on it. Pisse prophets aside, some physicians were offering diagnoses based on urine samples alone, without ever seeing the patients who provided them. But learning to read urine based on printed charts could be dangerous. As Duroselle-Melish says, printing technology wasn’t up to the task.

“Most of these images were printed in black and white,” she says. “For a lot of these illustrations, color was added after, by hand.”

Look more closely at the chart above: The colors don’t even match from one page to another. Color might have been added to an illustration by a printer, or it might have been commissioned by the owner of a book after purchase. There was no standardization, and while some book publishers created detailed coloring instructions, the artisans who did the work didn’t always conform to those specifications.

In this case, the unreliable coloring “makes the identification of the color and the diagnosis difficult,” says Duroselle-Melish. It certainly seemed impressive to have a book with a color illustration, but in this case it was still, in part, just for show. Any physician who wanted to master urinalysis would have to read the Latin, too.