TECHNOLOGICAL ANSWERS
TO RESTORATION

The growing need to preserve our cultural heritage is causing a rise in the demand for increasingly accurate cleaning techniques, featuring high selectivity and low impact.

CASI DI STUDIO

DOMITILLA'S CATACOMBS

BAKERS’ NICHE IN THE ROMAN CATACOMBS OF SAINT DOMITILLA - ROME

AUTHORITY RESPONSIBLE OF THE RESTORATION:  Pontificia Commissione di Archeologia Sacra - Roma

RESTORER:  Maria Gigliola Patrizi

Edited from “M. G. Patrizi, B. Mazzei, M. Mascalchi, S. Siano; Laser removal of dark film on frescoes in hypogean areas: the case study of the bakers’ niche in the catacombs of Domitilla in Rome, APLAR 3 conference proceedings,  Bari, July 18-19, 2010, Padua, 2010, pages 73-83”

 

HISTORY:

The bakers’ niche is located on the first floor of the catacombs of Domitilla. Its walls are mainly frescoed, often with dry overpainting. The microclimate inside the hypogean structures of the catacombs is usually     quite stable, featuring high relative humidity between  96% and 100%, and temperatures around 14-17°C all through the year. One of the most common decay problems concerns the precipitation and crystallization of calcium carbonate that covers the frescoes almost entirely. An instance of such decay is the typical dark film covering the vaults and the upper walls of the rooms that may range from thin films to very thick layers. 

LASER CLEANING METHODOLOGY:

During the last twenty years, the removal of incrustations has been carried out mostly manually, trying to remove the most of the concretion, at the same time protecting the original painting. Nevertheless, the results obtained with this method were unsatisfactory as they did not result in the complete cleaning of the surface. Therefore, two laser systems, Long Q-switch (EOS 1000 LQS) and Short Free Running (EOS 1000), have been tried for cleaning tests. The tests carried out with the LQS system have used 5Hz frequency and 0.7 J/cm2 fluence: the dark film was completely removed from all the shades of colors: white, green and ochre. When the layers showed particularly thick earth incrusting, the irradiation of the LQS was no longer enough. Therefore, the SFR system was used: to obtain the optimal results, different parameters were used in consecutive steps, and frequencies between 2.1 J/cm2  and 7.0 J/cm2 were used.

ADOPTED SYSTEM