Femtosecond Laser Cleaning of Metallic Antique Artworks - Advantages, Limits and Economic Aspects

Corrosion products and other contaminations of metallic artworks can often not be removed sufficiently by conventional conservation techniques. A laser cleaning method for antique metallic artworks using a femtosecond laser technology is presented. Due to the small thermal impact of this technology, compared to nanosecond laser ablation, damage or discolouring of the original surface is avoided. The selective removal of corrosion products from original objects made of copper, bronze alloy and silver, using a Titan-Sapphire femtosecond laser, is shown. Moreover, the influence of the laser fluence and of the number of cleaning cycles on the specific removal efficiency is presented leading to specific fluence thresholds. The maximum surface-specific cleaning rates are evaluated from the viewpoint of restoration in practice, so that an economic balance sheet including operating and labour costs is given for this technology.