The masterpiece was made in 1464-1470 by Hans Duringer.
The conservation of the clock started in May 2019. The object was cleaned from overpaint, then consolidated and some of preserved original parts of the framework were reassembled. To cover not original tree, leaves and apples were added. To cover the clock's base, an extra wooden covers were assembled. Some sculptures which were reconstructed in the nineties of XX century were corrected, for some like death and Madonna new polychrome was made. Adam, Eve, angels, deacons and snake's head were disassembled and will be replaced with new ones in 2020.
Pigments and silver leafs were identified with microscope methods. Study of transactions of oak wood showed some big vessels of this species.
Astronomical Clock / Cross sections
As usual blue paint was prepared with lazurite and applied on gray layer [sample 1]. Green parts of the clock's architecture were firstly covered with minimum layer [sample 2]. Paper stars were gilded and then glued onto the clock's surface. Silver leafs were burnished on bole/gesso layer [sample 3].
Cross-section from planetarium background shows paper star covered with silver. Stars were glued on the clock's surface before last lacquer were used.
Astronomical Clock / Cleaning
With deionized water and Shellsol T were chosen to remove dirt from surface.
Pigments and silver leafs were identified with microscope methods. Study of transections of oak wood shows big vessels of this species.
The surface was cover with Paraloid B72. Aerograf was used to made this layer.
cleaning disassembled parts of the clock
Astronomical Clock / Removing overpaint
To uncover original decoration, dull overpaint was removed.
The medieval clock decoration was darker  than colors used when it was repainted . Glaze was used by authors. After removing the secondary polychrome, a heterogeneous layer of paint appeared.
During removing overpaint, many damages of paint layer were revealed.
Astronomical Clock / Retouching
Retouching the areas of an artwork where paint is missing
Transparent paints were used to retouch. Dry pigments and Paraloid B72 were mixed to obtain paint for retouching.
right side with new polychrome
The sculptures added during the rebuild of the clock were covered with new polychrome.
New paint layer looks older to make reconstructions more similar to original parts. Background of Madonna's radial halo was covered with darkblue paint layer.
After conservation, sculptures made by Stanisław Wyrostek became more similar to the medieval figures.
Astronomical Clock / Tree of the knowledge of good and evil
Leaves & Apples
At the top of the clock, to cover the reconstructed tree of knowledge of good and evil, copper leaves and apples were added.
The leaves were covered with silver. All apples were made of araldite, and then connected to the leaves with a frame made of aluminum tape. These branches were then stiffened with araldite, after which the last layer of paint was made and silver patinated. The leaves were protected with a layer of Paraloid B44 and shellac.
Peper stars recontruction
The original paper stars were first examined. The best quality cotton paper with a weight of 80 g was chosen.
As in the pattern, a layer of glue from rabbit skin was applied, followed by a primer, a white bole and a final red or yellow bole layer.
It was important to recognize and copy the color and thickness of the shellac layer.