Enameled gold in the Green Vault

One of Saxony’s most famous museums is the Green Vault in Dresden Castle. Its treasures include the filigree enameled gold gems created by court jeweler Dinglinger representing the court of the Great Mogul of India. For decades these were exhibited in glass cabinets which released numerous pollutants. The result: the elaborate enameling gradually began to peel off. The fragments were meticulously collected and their position was registered – but the problem was how to fix them back on again. The conservation material is subject to extremely rigorous requirements: it has to be transparent, long-lasting and have similar properties to those of glass, while at the same time being capable of establishing a firm bond between enamel and metal.

“We developed a suitable material at the Fraunhofer Institute for Silicate Research ISC in Würzburg twenty years ago – enamel ORMOCER®: restorers were thrilled with it,” explains Dr. Gerhard Schottner, Head of Department at the ISC. This material not only ensures lasting conservation of enamel gems, it is also perfect for transparent and permanent bonding of ivory and rock crystal. There is one problem, however: the raw materials were no longer available in consistent quality. In this synthesis of silicon-organic compounds, even the slightest impurities can cause major differences. So what was to be done? “We need the very best material for cultural heritage preservation. But the amounts required are extremely small,” explains Schottner. For this reason, material development and sales are not profitable for a company geared towards economic success. The answer was the Executive Board Project along with funding provided by the German Federal Environmental Foundation.

The ISC teams examined and analyzed the raw materials as well as the individual production stages down to the smallest detail, fine-tuned the reaction conditions such as moisture levels and looked into the impact of various solvents. The process is now almost complete: the material is in the final testing phase and the restorer involved – Rainer Richter of the Dresden State Art Collections – is extremely satisfied.