ABSTRACT
The preservation and restoration of paintings are delicate tasks that involve removing dust, varnish, or overpainting without damaging the original material. Traditional chemical cleaning methods have limitations, especially when faced with frames containing sensitive paints. An alternative is laser cleaning. Laser cleaning involves the selective absorption of laser energy by contaminants, allowing for controlled removal. This study focuses on the restoration of the Issenheim altarpiece frames of Matthias Grünewald (1512-1516), painted in tempera and oil.bTwo types of lasers were tested for the cleaning process: Nd:YAG, LQS and SFR 1064 nm and Er:YAG 2940 nm. Optical coherence tomography (OCT) was used for the evaluation of the cleaning, providing valuable insights into the composition, structure, and conservation needs of the frames. The results of the laser cleaning tests showed that the Er:YAG laser in Very Short (150 µs) mode was effective in removing residues from the frames, but the original paint was sensitive to the laser treatment. The Nd:YAG laser in LQS (100 ns) mode demonstrated potential for selective cleaning. It al-lows for the restoration of the original appearance of the frames while minimizing the risk of irreversible damage. The study highlights the importance of selecting appropriate laser parameters, closely monitoring the cleaning process, and utilizing advanced imaging techniques like OCT for evaluation. Continuing research is being conducted to further understand the mechanisms of destructuring induced by lasers on paintings. In conclusion, this research contributes to the ongoing exploration of laser cleaning in heritage conservation and restoration, emphasizing the need for skill transfer and collaboration between professionals and heritage laboratories.
