It’s a Wash

May 2, 2018
Assistant paper conservator Christina Taylor places a 16th–17th-century Dutch print into a water bath, a technique conservators use to clean works on paper.

One of the most common methods for cleaning works on paper may also be the most surprising to non-conservators: water baths.

In conservation labs around the world—and right here in our own Straus Center for Conservation and Technical Studies—original drawings and prints on paper are often cleaned by being sprayed with, or even submerged in, water. “Washing works of art on paper is an effective way to treat a variety of problems at once,” said Anne Driesse, senior conservator of works on paper. “As long as the artwork—both support (paper) and media—can withstand prolonged exposure to water, washing a work is good” for removing such imperfections as stains and discoloration.  

Pre-Treatment Precautions

Long before any liquid meets paper, however, conservators must determine whether using a water bath is in fact the best way to treat the work in question. They look closely at the object’s history and the desired outcome of treatment. As Driesse said, “We proceed quite slowly.”

Through a series of tests on minuscule areas of the object, both the paper and the media are assessed. Tiny droplets of conditioned wash water are placed on the object and immediately blotted to check for a reaction. (Sometimes, this is even done under a microscope.) Subsequent spot tests may occur for progressively longer periods to determine whether prolonged moisture contact affects the media. 

If the media and support are deemed stable, the next step is to select the method of washing. Options include fully immersing a work; “float washing,” or floating a work on the surface of a bath (thereby not fully immersing both sides); and “suction washing,” conducted atop a table with many small holes and a vacuum that pulls cleaning solution (and, it is hoped, any discolored elements from the paper or media) into blotters.

Another important step is deciding which formulation of water is appropriate. Tap water is never used; it contains far too many imperfections and chemicals (such as chlorine). Instead, conservators start with deionized water and slowly “condition” it by adding small amounts of ions until the water reaches a target pH level (correlated with the actual object’s pH level). This important step ensures that the water won’t damage the art.

A Warm—and Effective—Bath

Recently, assistant paper conservator Christina Taylor was treating a 16th- to 17th-century Dutch print that had become discolored. At some point in its history, the print was affixed to a backing sheet of paper; Taylor hoped to separate the two.

Testing and research revealed that the ink used for the print was oil-based and not water-sensitive. The paper was presumed to contain rag material, which generally ages and withstands treatment better than some 19th- or 20th-century papers. Based on these factors, she felt it would be possible to submerge the object without risk of damage.

First, Taylor introduced humidity by resting the work between two layers of Gore-Tex (a synthetic waterproof material) within a humidity chamber. After an hour, she lightly sprayed it with conditioned water. “You always want to prepare the work gradually; you never take a work on paper from completely dry to totally wet,” she said.

Next, she filled a small tub with warm, conditioned water. Holding the dampened print between thin sheets of polyester (which helped her avoid directly touching the print), she lifted it out of the humidity chamber and into the tub. Gently, she pushed the print below the water, and then removed the top layer of polyester.

It’s important to note that neither Taylor nor Driesse shies away from directly touching a work of art with clean bare hands when necessary. Paper conservators rely on their sense of touch to gently handle works of art and to ensure that the very act of handling doesn’t cause damage. Wearing gloves—commonly misperceived as an appropriate technique in many situations—would add a layer of distance between conservators and the work, and the loss of tactility could inadvertently present a greater risk to the art than any oils from the fingertips.

Holding the polyester layers surrounding the print, Taylor lowers the work into the water.

After just a few minutes, Taylor noticed tiny bubbles form around the edges of the print, indicating that it had begun to separate from the backing paper. She gently inserted a small spatula underneath the print’s edges. “I’m hardly applying any pressure at all, and it’s coming right off,” she said.

Taylor begins to gently separate the print from a backing layer of paper.

To make the removal even easier for her to observe the process, she decided to work on a light table. Within minutes, she had detached the print.

  • On a light table, Taylor completely removes the soaked backing paper from the print.

  • After returning the print to the water for a short period of time, Taylor noticed that the water was starting to discolor—a sign of the water bath’s effectiveness.

After a second bath—and the removal of further discoloration and old mounting adhesive (evidenced by the pale yellow water left behind in the tub)—it was time to dry the print. Taylor air-dried the work until it was merely damp to the touch, and then placed it between layers of blotter (thick, very absorbent paper). She periodically switched the blotters with dry ones over the course of several days.

A few weeks later, Taylor completed the treatment by filling a small loss at the bottom edge of the print with paper pulp, and drafted a formal treatment report work for the object’s record. Later this year, her hard work can be appreciated by a wider audience: the print will be featured in a gallery installation.

When Less Is More

On the other side of the paper lab, Driesse was busy cleaning another work, Winslow Homer’s Men Beaching a Boat (1881–82). Her preliminary testing had revealed that the media (black chalk) and paper were more sensitive than the print Taylor had worked on, so she took a more conservative approach.

  • of Senior conservator of works on paper Anne Driesse prepares conditioned water for use in a water bath.
  • of Driesse sprays the verso (reverse) of a drawing with a cleaning agent.
  • of Driesse prepares to float the work on the water’s surface.
  • of With the work now floating on the surface, Driesse keeps a very close watch on it. This particular drawing is Winslow Homer’s Men Beaching a Boat (1881–82).

Rather than one or two lengthy baths, she gave Homer’s drawing a series of 10- to 15-minute float washes. Between those she treated the drawing with a specified agent to target areas of discoloration. She also used a suction table to remove degradation. Through this multipronged approach, she was able to achieve a dramatically cleaner overall appearance for the drawing. (See the slider below to appreciate the difference.)

There may be no shortcuts or “one size fits all” solutions when it comes to washing works on paper, but the outcomes are almost always the same: each work is brought much closer to its original appearance.