Sticky tape was first invented in the mid-19th century, and it’s been making conservators’ lives hell ever since.
“Tape is the bane of the conservator’s existence,” says Margaret Holben Ellis, a professor of paper conservation at New York University. The problem is simply that tape works too well. Removing it can easily take off a layer of paper, and adhesives from old tape can sink into paper, staining it an unsightly yellow or brown.
You can’t really blame people for using tape, says Elissa O’Loughlin, a former conservator at the Walters Art Museum, who co-teaches a five-day course on paper conservation. “It’s just human nature,” she says. “It was seen as a miracle product.” Pressure-sensitive tape, to use the official term, is much more convenient and easy to use compared to older adhesives that required heat or water. Of course, people would use it to repair rips in drawings and documents, without thinking of conservators in the future.
Removing tape is challenging because no two cases are the same. Depending on the type of tape, the type of paper, and the type of ink on the paper, you have to use different techniques.
So the first thing to do is identify the type of tape, which is why O’Loughlin travels with “70 pounds of historical tape examples” when teaching her tape-removal class. They fall into two broad categories: the acrylic-based tape most recognizable as Scotch tape, and rubber-based tapes used in the early 20th century. The second type, says O’Loughlin, “brings horror to the mind of most conservators.” It is notorious for staining paper.
(People in the past have also been, let’s say, creative. Ellis says she’s also seen postage stamps, band-aids, and surgical tape. “People have this concept that if it’s safe to use on a person after surgery, it must be safe to use on art,” she says. Pro tip: “It’s not the case.”)
Conservators often remove Scotch tape by using a stream of hot air to soften the adhesive. Or they remove it mechanically, with a microscope and carefully wielded tool. The older rubber tapes, especially the ones that stain, need solvents to dissolve the adhesive. A conservator can float an entire sheet of paper in a bath of solvent, so long as the chosen solvent does not dissolve dyes or ink. They may also place the object into a vapor chamber, where vaporized solvent slowly dissolves the adhesive.
If more precision is necessary, conservators can use a pipette to apply tiny drops of solvent only where the adhesive is. They do this on top of a suction table, which has a porous surface that sucks the solvent down through the paper and into the table. This stops the solvent’s natural tendency to spread across the paper.
In a recent paper, a group at the University of Florence reported on a possibly more precise way of using solvents on paper: by trapping them in a gel. The gel, which Piero Baglioni, an author of the study, likened to contact lenses, confines the solvent inside a matrix of molecules, allowing it work on tape adhesive without penetrating deeper into the paper. The idea comes from painting conservators, who already use similar gels. A paper conservator, Antonio Mirabile, used Baglioni’s gels to remove tape from a handful of drawings —including a sketch of a scene from the Sistine Chapel where where they found an inscription that reads di mano di Michelangelo (“from Michelangelo’s hand”) under the tape. (Baglioni doesn’t actually think the sketch was done by Michelangelo, and their journal article suggests a collector may have used tape to cover up the false inscription.)
But using solvent gels on paper is a new technique, and the paper conservators wanted more evidence of its efficacy and safety. “We tend to be cautious people. We tend to like a lot of evidence before we proceed in treating irreplaceable works of art,” says Ellis. Paper, after all, is one of the most fragile materials. It’s difficult to work with, but also rewarding.
“I love paper,” says Ellis. “It’s high-risk. It’s not as forgiving as other substances.”