For centuries, ivory has often been used to make art objects. But to protect elephant populations, the ivory trade was banned internationally in 1989. To restore the ivory parts of ancient art objects, it is therefore necessary to resort to substitute materials – such as bones, shells or plastic. However, there is not yet a really satisfactory solution.
TU Wien (Vienna) and the 3D printing company Cubicure GmbH, established as a spin-off of TU Wien, have now developed a high-tech substitute in cooperation with the department of the Archdiocese of Vienna for the care of the Addison’s art and monuments and restoration: the new “Digory” material consists of synthetic resin and calcium phosphate particles. It is processed in a hot, liquid state and cured in the 3D printer with UV rays, exactly in the desired shape. It can then be polished and matched to create a deceptively authentic ivory substitute.
Beautiful and mechanically stable
“The research project started with a precious 17th-century state coffin in the parish church in Mauerbach,” explains Professor Jürgen Stampfl of the Institute for Materials Science and Technology at TU Wien. “It is decorated with small ivory ornaments, some of which have been lost over time. The question was whether they could be replaced by 3D printing technology.”
The team already had experience with similar materials: the research group also works with ceramic materials for dental technology, for example. Nevertheless, it was difficult to develop a suitable substitute for ivory: “We had to meet a whole series of requirements at the same time,” says Thaddäa Rath, who worked on the project as part of his thesis. “The material should not only look like ivory, the strength and stiffness should also be correct, and the material should be machinable.”
Stereolithography in the 3D printer
Through many experiments, Thaddäa Rath and other members of the TU Wien and Cubicure team managed to find the right mixture: tiny particles of calcium phosphate with an average diameter of about 7? M were embedded in a special resin, as well as extremely fine silicon oxide. powder. The mixture is then processed at high temperature in Cubicure’s 3D printers using the hot lithography process: layer by layer, the material is cured with a UV laser until the complete object is completed.
“You should also keep in mind that ivory is translucent,” says Thaddäa Rath. “Only if you use the right amount of calcium phosphate will the material have the same translucent properties as ivory.” Then the color of the object can be retouched – the team achieved good results with black tea. The characteristic dark lines that normally run through ivory can also be applied later with great precision.
No more defenses!
In the field of restoration, this is a big step forward: with the new “Digory” material, not only a better, more beautiful and easier to work with available ivory substitute than before, 3D technology allows also to reproduce the smallest details automatically. Instead of painstakingly carving them out of an ivory substitute material, items can now be printed in hours.
“With our specially developed 3D printing systems, we process different material formulations for completely different areas of application, but this project was also something new for us,” says Konstanze Seidler of Cubicure. “In any case, it is further proof of the diversity of possible applications of stereolithography.”
The team hopes that the new “Digory” material will be widely accepted in the future – as a high-quality aesthetic and mechanical substitute for ivory, for which no elephant should lose a tusk.
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Material provided by Vienna University of Technology. Note: Content can be changed for style and length.