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A bandage for sick works of art

A “bandage” that removes adhesive from paper-based works of art will help museum curators, conservators and collectors in their struggle to save Europe’s art heritage from the ravages of time. Mounted prints, drawings and photographs can be damaged by changes in humidity or temperature because their paper expands and contracts at different rates from the mount material beneath. The new bandage carries an enzyme that softens the starch-based mounting adhesive, allowing the work of art to be safely removed from the mount.

The product developed by the team members of EUREKA project EU 1495 — EUROCARE-ENZYMGEL is easy to use and cheap enough for tight museum budgets. The art world has already shown a great deal of interest in the technique, and when the bandage goes on sale in 1998 the developers expect it to become a standard item in the conservation workshop.

Starch: the natural glue

Starch, for centuries one of the few adhesives available, remains a very good glue for mounting prints and drawings, explains Professor Gerhard Banik of the Staatliche Akademie der Bildenden Künste in Stuttgart, Germany. The problems start when the humidity changes and the mount expands or contracts. The print, which is on a different type of paper and is generally much weaker than the mount, can be creased, cockled and even torn as it expands and contracts to a different extent.

The problem is made worse by the 19th-century habit of adding aluminium sulphate to the starch to make a stronger glue. Over the years the mixture of alum and starch hardens, increasing the likelihood that the print will be damaged and making the glue very difficult to remove. The challenge was to find a way to remove the hardened glue quickly and simply.

The Albertina Collection in Vienna, dating from the early 19th century, is one of Austria’s most important collections of graphic art. It contains thousands of rare prints and drawings pasted into albums, many of them in urgent need of conservation. In 1989 Professor Banik and his staff started working with conservators from the Albertina in an effort to find a way to remove hardened starch glue. The team experimented with amylase, a natural enzyme found in saliva which attacks starch, but the trials were unsuccessful and the project languished.

A quick and easy solution

In October 1995 the partners decided to re-start the work as a EUREKA project. The Albertina became the project leader, and the Austrian subsidiary of German chemical manufacturer Henkel joined as a third partner to supply materials and expertise in laboratory techniques. “We were looking for a method of starch removal that could be carried out with the minimum of special care,” Professor Banik explains. “In European collections there are hundreds of thousands of works of art needing treatment. Many conservation departments do not even have their own laboratories, and they do not have big budgets either. So our solution had to be something that was inexpensive and that could be used straight out of the box.”

The team started work with a mixture of methylcellulose, a gum-like thickening agent, with amylase and other additives including gelatine to help the enzyme work under conditions of low humidity. By late 1996 they had a working prototype in the form of a starch-softening gel. To use it, a piece of paper was placed over each glue spot, a drop of gel was placed on top and covered with a plastic film to stop it from drying out. The enzyme gradually diffused through the paper, and once it had softened the starch the drawing could be lifted away from the mount.

Tests first on dummy materials and later on real prints at the Albertina showed that the gel was easy to use and worked well. However, it had a limited shelf life that would pose problems in everyday use. There was also a commercial difficulty: Henkel owned a patent on the product but was not interested in marketing it. “When we published our results there was a lot of interest from other art conservators,” says Professor Banik, “but we didn’t have a commercial product. We couldn’t sell it, and we couldn’t talk about how it was made.”

To get over the shelf-life problem the team set about developing a second version in which the chemicals are carried as a dry mixture on a sheet of thin polypropylene fleece. “It’s a sort of poultice,” says Professor Banik. “You cut a piece to size, place it on the glued area and then moisten it. It’s easy to use, it gives consistent results and because it uses only a very small quantity of enzyme it doesn’t damage the print.”

The new poultice will be marketed by a commercial partner outside the EUREKA project: Walter Klug & Co. of Immenstadt, Bavaria, a company that sells paper and other materials for conservation purposes. The team members have yet to do a formal marketing study, but Professor Banik is confident that they are on to a winner. “The material to treat the Albertina Collection alone will cost several million Schillings,” he says, “and then there are all the other art collections across Europe with the same problem. This is going to become a standard tool for conservators.”

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