Perhaps you can't judge a book by its cover, but there's a wealth of information to be gleaned from its scent.
A new testing method can rapidly determine the condition of old books and documents by analyzing the bouquet of volatile organic compounds released by paper off-gassing. The technology promises to help conservators assess the condition of old works quickly, while not harming the documents.
"Paper emits more than 200 various compounds of which on the basis of our research we were able to pinpoint to 10 or 15 compounds that carry the most information about the composition of paper," said Matija Strlie, lead researcher and senior lecturer at the Center for Sustainable Heritage at the University College London.
Strlie and his team surveyed the VOC emissions from 72 paper samples in different stages of decay. From those results, the researchers developed a series of scent markers for the structural stability of documents, books and other paper materials.
The familiar odors of old books, which Strlie's study describes as "a combination of grassy notes with a tang of acids and a hint of vanilla" varies depending on the chemical reactions and oxidation rates of paper ingredients, such as ash, cellulose, rosin and lignin.
The paper manufacturing era of each book can also reveals a lot about its condition.
"It's really the technology revolution after 1850 that led to what we call 'acid paper' that degrades very rapidly," Strlie told Discovery News. "Today, for books produced from 1890 to 1900, the pages are already very brittle."
With current testing technology, analyzing such fragile books and heritage documents for preservation and exhibition is often a tedious process. This new scent test, however, could save conservators time and allow them to examine the papers nondestructively.
"Today's technology is, generally speaking, very sufficient. However, the challenge in analyzing historical paper is that we are in need of non-destructive, non-invasive analytical tools," said Gerrit de Bruin, head of conservation for the National Archives of the Netherlands, who has also studied paper testing.
Book conservators have multiple testing methods at their disposal, including pH analysis, paper folding and infrared spectroscopy, but most require handling or sampling, which could potentially damage the delicate documents.
"Water stains on the paper, even when they are dried up by the conservator, and not visible directly after pH measuring, can give side effects such as so called 'tide lines' (lines caused by dirt shifting in the paper) in the near future," de Bruin said.
As Strlie continues to refine the scent testing method, he hopes to apply the technology to portable "handheld electronic noses" that conservators could easily use.
The tool could be particularly beneficial for book conservators like Vanessa Haight Smith, who works with the Smithsonian Library's collection of 1.5 million works.
Due to the myriad factors that contribute to paper degradation — including water damage, insect droppings and environmental conditions — and the time-consuming process of surveying older paper products, Smith says the Smithsonian usually requires a year to prepare exhibition pieces.
"[The smell test technology] would be very helpful because in our site we're limited in staff and time, and if we know the chemical breakdown or molecules to a certain level, we can treat it more directly and appropriately," Smith told Discovery News.