Science and Soil
CANR’s Soil Testing Lab began in 1947 as a public service to help farmers identify optimal amounts of lime or fertilizer for their crops. Today, the lab still tests soil for farmers and home gardeners, and it also provides analytical services for researchers across campus, testing soil, water and plant samples, as well as research materials like bones, food and archeology samples. And, wildly enough, even books.
The lab confirmed dangerous levels of arsenic in Tedone’s emerald green book. And although Tedone’s suspicions were correct, the news still came as a shock. “It’s one thing to use a pigment like that in a small area in an illustration or painting, but this was the entire book just covered with it,” Tedone said.
Tedone and Grayburn developed a protocol for testing other green books in the Winterthur library and created the Poison Book Project to document their progress. To date, they have tested approximately 350 green books from Winterthur’s collection, about 10% of which contained arsenic. Other institutions are adding their positive arsenical books to the database as well.
Identifying a “poison book” is a four-step process, Grayburn explained, beginning with visual identification. The green hue is so distinctive that simply looking at the book cover can determine which books should be tested further.
Next, conservat[ors] use two standard technologies to identify chemical compounds: X-ray fluorescence and Raman spectroscopy. The first, commonly called XRF, identifies elements present in an object, such as arsenic and copper. These tests can be done easily with a hand-held tool that is as simple as using a bar scanner.
If the suspected elements are found, Raman spectroscopy provides in-depth analysis that identifies specific pigments, such as emerald green. Spectrometers are larger, non-portable machines, making them less common.