Books might contain timeless wisdom, but the objects themselves aren’t immortal. In addition to normal wear and tear, they can succumb to mold, pests, environmental hazards, and other threats if not stored and handled properly. Book conservators are the people who help repair this damage, preserving and protecting books for future readers. We spoke with a few of these experts to learn more about the job, from their favorite projects to the surprising utility of commercial freezers.

1. THERE'S NO SINGLE PATH INTO THE FIELD.

According to Mindell Dubansky, head of book conservation at the Metropolitan Museum of Art, becoming a book conservator requires an intensive mixture of hands-on and academic experience. "It's very challenging because there aren’t that many formal educational opportunities," she says, "and [the route] is not that straightforward."

People may get into book conservation through bench training (i.e. learning on the job as a lab technician), working in a commercial bookbindery, taking bookbinding classes, earning a degree from a handful of specialized trade schools, or going through a book arts, material culture, or library science master’s program. But Dubansky says that where you study—and the collections you have at your disposal—will shape your skill set and determine the course of your career. She herself received an undergraduate arts degree from Carnegie Mellon before studying bookbinding and restoration at what's now London's Camberwell College of Arts. She later earned her master's in library science and a certificate in library preservation from Columbia University. Today at the Met, she works on a collection that includes everything from artists' sketchbooks to Beethoven's funeral invitations.

2. THEY NEED TO BE GOOD WITH THEIR HANDS.

Loving books is great, Dubansky says, but it's no substitute for fine motor skills: Conservators spend lots of time sewing, measuring, gluing, rebinding, handling sharp objects like knives, and treating books with chemicals. She recommends that aspiring book conservators take basic bookbinding classes before deciding whether to pursue a career in the field. The experience should let them know whether they enjoy working with their hands, something they'll be doing frequently once they become full-fledged professionals.

"The process [of bookbinding] is simple but requires great accuracy," Dubansky says. That accuracy becomes even more important when you transition from a bookbinding class to on-the-job conservation.

3. OLD BOOKS CAN BE EASIER TO RESTORE THAN NEW BOOKS.

You might think that centuries-old books are always more fragile than newer works. But Katie Wagner, a rare book conservator for the Smithsonian Libraries, says that's not always the case: "We have books from our collection that are hundreds of years old, and that paper is in better shape than modern paper. That’s because the process of making paper from cotton and linen changed around 1840. They started incorporating wood pulp and they weren’t de-acidifying it first." When paper becomes too acidic, it degrades and turns hard.

As a result, even well-made books from the late 19th century onward can be brittle to the touch. "If a book is pre-1840, it's often easier to restore than a book from 1940," Wagner says.

4. THE MAIN TOOLS OF THE TRADE HAVEN’T CHANGED FOR CENTURIES.

“If a bookbinder from the 19th century walked into our room [at the Met], they would feel very much at home,” Dubansky says. Book conservators have used the same equipment for hundreds of years, from basic hand tools like bone folders (used to make sharp creases in paper and other materials) to thread and needles used to re-sew tattered tomes.

Changing technologies have added new techniques to the mix, of course, “but day to day, it’s the basic tools that we probably use the most,” Wagner says.

5. SOME CONSERVATION TECHNIQUES ARE SURPRISINGLY BASIC.

Even schoolroom supplies can find new life in a conservation department. Take, for example, the humble eraser. Victorian-era volumes sometimes have sooty pages if they were housed near coal-burning furnaces, and according to Wagner, erasers can remove this residue. But since the pressure of a regular eraser’s point can cause streaks and lines to form on the page, bookbinding supply companies sell ground-up eraser crumbs, which conservators sprinkle onto pages and then rub in circles. Once the white eraser crumbs have turned black, they’re carefully brushed from the page, and new layers of crumbs are applied until the stains have faded. (Not all conservationists opt for erasers, though; some prefer to use small rubber sponges called soot sponges.)

Another conservation technique involves an appliance you might not expect: When conservators spot mold growing on a book, they stick the volume inside a commercial freezer, which Wagner says inhibits growth.

6. EVERY DAY ON THE JOB IS DIFFERENT …

No two books (or their materials) are exactly alike, which keeps the job fresh and interesting. "I'm always getting something new to treat," Wagner says. Books from different eras and places vary in their materials and construction, as well as in the kinds of traumas they've experienced, whether it's water or insect damage or mold exposure. Amateur fixes from prior owners—a taped page, for example—can inflict their own kind of damage.

Repairs can include re-backing books, patching tiny holes and tatters with Japanese paper (it's thin and strong), humidifying paper to separate stuck pages, and deciding which methods of treating stains work best with the book's ink and materials. Some books might be good candidates for washing using de-ionized water—which can remove dirt and debris—although this method isn't conservators' first line of treatment, since it changes the structure of paper.

"You have to look at each object as its own entity and decide what’s best for it," Wagner says.

7. ... BUT LIKE ALL JOBS, THERE ARE DULL MOMENTS.

When they’re not repairing old tomes, book conservators can sometimes be found tackling paperwork of a different sort. “For every rare book I treat, I have to write a condition report,” Wagner says. “When that book comes in I have to photograph it, and I have to note its size, its condition, how it’s bound, and the problems it’s having. That can be time-consuming."

8. THE BEST CONSERVATION JOBS ARE INVISIBLE.

A conservator’s job typically isn’t to make an old book look like new again (unless it’s, say, going on display in a period room), but to make it readable using as little work as possible. “I’m not going to rebind a book because it’s old and beat-up,” Dubansky says. “I treasure the fact that it’s old and beat-up. What I’m going to try to do is repair all the parts that are vulnerable to make it functional.”

9. THEY OFTEN FREELANCE.

Book conservators can be found working at bookbinderies, museums, college and university libraries, public libraries, and other types of institutions. Some, however, also tackle freelance projects on the side, working with clients to restore items like tattered family Bibles, old journals, and heirloom books. Many conservators are also self-employed: Instead of working a 9-to-5 at a single institution, they'll work part-time or with institutions or private individuals on a project-by-project basis.

10. DIGITIZATION HELPS SAVE OLD BOOKS.

Some books are beyond repair, like when they're "so brittle that they're breaking to the touch," Wagner says. In that case, the book may be a good candidate for digitization, since at least then the subject matter will be available to researchers. Conservators will use special copiers or take individual photos of each page ("very, very carefully") to immortalize the words without harming the book itself.

11. THEY SOMETIMES GET TO WORK ON HISTORY-CHANGING DOCUMENTS.

In 2013, a life-changing first edition passed through Wagner's hands: Edward Jenner’s An Inquiry into the Causes and Effects of the Variolae Vaccinae (1798), which details the English physician's work with what would ultimately become the smallpox vaccine. "That was amazing because he’s the father of immunology," Wagner says.

While rare and influential, the book itself wasn't in great condition. Its inside pages were covered in mold, and its stitching had unraveled so that sections were detached from the binding, among other damage. The first thing Wagner did to treat the book was to stick it into the freezer to blast its mold. Then, after dry cleaning it with a brush, she dismantled the book's text block (a.k.a. the "block" formed by a book's cut and stacked pages), washed individual pages in de-ionized water, and humidified and dried the color plates. Wagner then patched holes from mold growth with Japanese paper before re-sewing them together and re-casing them in their original binding.

Wagner says she still remembers the project because of the amount of labor that went into it—and the importance of the book in medical history, now preserved for future generations to enjoy.