Preservation of the Hermitage's historical porcelain collection

The Museum of the Imperial Porcelain Factory, managed by the State Hermitage Museum in St. Petersburg, is a unique place where the rarest works and works of art are kept. The porcelain collections contain exhibits that reflect the history and culture of Russia for several centuries. One of the historical gems of the museum is a series of porcelain figurines called "Nationalities of Russia", created in 1907−1917 by the author P. P. Kamensky. The collection has no analogues in its unique design and technique. Despite the quality and durability of the porcelain products, time and circumstances can cause irreparable damage to the exhibits. That is why one of the tasks of the Imperial Porcelain Factory is to preserve and recreate the collection. It was performed using modern 3D scanning techniques. The project was implemented jointly with the State Hermitage Museum and the Kiberon Group company, professionals in the field of 3D technologies.

There are 74 figures in the collection, which range in height from 36 to 40 cm. The Kiberon Group had the task of digitizing 28 figures: after processing the scan results, their three-dimensional models were prepared to create a digital archive of the collection. The same 3D models were used to create copies of gypsum polymer sculptures through 3D printing. A 3D scanner of the "PRO" line from RangeVision, a leader in the development and production of professional 3D scanners and related software in Russia, was used to digitize the figures. Cyberon Group specialists conducted 3D scanning on the museum’s territory.

Anna Ishchenko, a 3D designer at Cyberon Group, spoke about the difficulties she faced in the process of digitizing porcelain figures.:

• "The whole complexity and responsibility of the project was as follows:
• The sculptures are more than 100 years old. Any tactile manipulation of them was excluded. The entire process took place in the presence of museum staff, and any movement of exhibits was carried out with their help and under their supervision.
• Most of the sculptures in the painting are black or even in dark blue or black color gradations. Dark colors have a poor reflection coefficient, which can lead to the scanner simply not "seeing" the object. This is the specifics of the technology. Not every 3D scanner has the ability to scan dark and black objects.
• The porcelain material has its own glossiness and luster, which greatly complicates the process. Usually, shiny objects are coated with a matting spray before 3D scanning. But in this case, its use was not possible due to the age and value of the figures.
• High-precision scanning was required to create copies as close as possible to the original. In this regard, the sculptures were scanned in sections, not in their entirety."

How was such a difficult task accomplished?

The RangeVision "PRO" 3D scanner is customizable: it has four scanning zones for objects of various sizes. This made it possible to choose the optimal area in terms of the size of the object and the required quality of the final model. The surface of the sculptures was digitized in the second scanning area, the size of which is 300*225*225 mm. At the same time, the 3D resolution was ~ 0.17 mm. To simplify the task and due to the limitations on manipulating sculptures, a turntable was used for scanning. The object on the turntable rotated 360 degrees in 12 turns.

It was possible to achieve the maximum amount of information about the object for the light figures by making three groups of scans:

• The first group of scans was captured with the scanner pointing from bottom to top, at an angle of 45 degrees;
• The second one is at a 90—degree angle (scanning the middle of the sculpture);
• The third is when the scanner is directed from top to bottom, at an angle of 45 degrees.

There were 6 such stages for dark and black-colored figures. The situation with figures in black/dark gradations was complicated by the fact that for successful scanning it was necessary to "light up the object", thereby obtaining a reflection of light from it. But in addition to the black color, there were light shades in the painting (face, hands, patterns on clothes). The result was achieved thanks to the variable exposure settings of the RangeVision 3D scanner. The scan was repeated at standard exposure settings and at exposure magnified 2−3 times. This eliminated the "over-illumination" on the object that occurs when lighting porcelain, in conditions that do not allow the use of a matting spray. For sculptures with very complex, deep details in clothing, additional scanning was performed in the supine position of the object, in which the scanner could "see" the folds and depressions.

"As a result of the work, we received 4−5 groups of scans for light shapes and 10 for dark ones. A meaningful and convenient amount of information for post—processing," says Anna.

After digitization of the exhibits, post-processing of the results was carried out. The initial stitching and processing of the scans took place in the scanner’s bundled software, RangeVision ScanCenter, which allowed combining groups of scans in automatic mode, which accelerated and facilitated the work. In the presence of groups with repeating geometry, the scans were combined manually point-by-point. The final preparation of the models and fitting to size, taking into account the shrinkage of the materials of further production, was carried out in the Blender program. As a result, 3D models in the STL format were obtained.

The gypsum polymer copy obtained by printing on a 3D printer was used to create a plaster mold, which was refined by the artists of the Imperial Porcelain Factory, taking into account modern technological features of production. Then the future product was cast into these molds and subjected to a double high-temperature firing.

The final stage of replica creation is the exact copying of the painting from the original museum. The copying of the sample and the subsequent painting of each product are carried out manually in the workshop of highly artistic products, taking into account the color nuances and the smallest details. Thanks to the professionalism of the sculptors and artists of the Imperial Porcelain Factory, the experience of the specialists of the Kiberon Group company, and high-precision RangeVision 3D scanning equipment, it was possible to carry out a large-scale project to preserve and recreate the "Peoples of Russia" collection, significant for the history.