Читать книгу Monument Future - Siegfried Siegesmund - Страница 17

Expert reports form the basis for the decision-making concerning conservation measures on marble and sandstone sculptures. However, in the dialogue between the experts, quantitative results in the expert reports are transformed into lingual assessments using subjective expressions such as “weakly/strongly affected” or “little/highly endangered”. In this way, primarily objective measurement values obtain a subjectively tinged interpretation.

Against this background it is the goal of the Risk Number concept to replace a subjective assessment with a preferably objective and quantitative evaluation. The Risk Number is defined as the product of a Measurement Number M(i) and a Valuation Number B(i):

R(i) = M(i) * B(i)

The Measurement Number M(i) constitutes a measured parameter (i) in the form of a dimensionless value. It is calculated by scaling the actual measurement values to the original condition of the object.

The Valuation Number B(i) indicates the effect of the relevant parameter (i) regarding weathering grade and risk of damage.

For the calculation of the Overall Risk Number R(total) of a sculpture, 104 different parameters are evaluated, which are assigned to 10 Excel data sheets representing the following categories:

1 Object Description

2 Art Historical Evaluation

3 Restoration History

4 Environment / Exogenous Risk Factors

5 Natural Stone / Endogenous Risk Factors; calculated separately for marble and sandstone

6 Damage Caused by Human Beings / Vandalism

7 Mechanical Damage / Loss of Material

8 Surface Alteration

9 Ultrasonic Diagnosis

10 Evaluation of Overall Risk Number

For each of these parameters and for each data sheet a separate Risk Number R(i) is calculated. These are summarized to the Overall Risk Number R(total), which expresses the risk the object under consideration is exposed to. The design of the calculation method causes the Risk Number to be a number between zero and one.

Due to a purely mathematical implementation of the measured values, the Risk Number represents an objective and quantitative assessment of the state of damage condition and risk damage.

So far, the application of a Risk Number is intended for marble and sandstone sculptures. An overall 36Risk Number R(total) has been calculated for altogether 8 sculptures and 4 tombstones.

The sculptures include: Apollo, Vestal Verging (both Carrara marble, Neue Kammern, Sanssouci Palace garden, Potsdam), the Flora Aeolus (both Laas marble, Garden of Nymphenburg Palace, Munich), Hera (original), Hera (copy), Rhea (original), and Rhea (copy) (all Cotta sandstone, Baroque Garden, Großsedlitz near Dresden).

The Tombstones from Jewish Cemeteries are: Baiersdorf/Erlangen: Bernhard Ehrenbacher, Siegmund Sulzberger, Loew Ganz (all Schilfsandsteine), No. 1091, Double tomb (red Buntsandstein)

The Total Risk Numbers R(total) calculated for these objects vary from 0.36 (tombstone No. 1091 to 0.64 (sandstone sculptures Hera and Rhea).