dc.description.abstract | In recent decades, lasers have become the devices that came out of research laboratories and are widely used
in industry, engineering, medicine, arts, etc. Among the many applications, lasers have found a place in the
conservation of cultural heritage as a source of radiation in the modern diagnostic techniques, cleaning and
scanning objects of priceless value [1]. Their importance in cleaning of cultural heritage objects is based on
the properties of these techniques, such as high sensitivity, nondestructivity, selectivity, flexibility, on-site
applicability and others.
Laser techniques application in metal artifacts cleaning has to be carefully evaluated due to complex
phenomena in laser–metal interaction and specificity of every artifact item. There is a large variety of metal
materials and their combinations in cultural heritage. Also, the different organic and inorganic encrustations
and corrosion products in different progression stage can be found on artifacts surfaces [2,3].
Therefore, the optimization of laser parameters for safe and effective metal artifacts cleaning process is
important step in order to avoid unwanted side-effects such as changes in the color or grater surface damages.
A specific field of the metal surface laser cleaning is the cleaning of thin metal foils and coated surfaces. In
cultural heritage such examples are metal yarns on the textile embroidery [4, 5]. Often, these yarns are coated
with some precious metal as are silver or gold.
This paper presents a study of laser cleaning parameters for safe and effective cleaning of silver coated copper
metal yarns. In that purpose the preliminary investigation are performed on silver coated copper plate. That
investigation involve numerical modeling of laser– silver coated copper plate interaction and experimental
irradiation of real sample surface with pulsed nanosecond Nd:YAG laser by changing laser parameters as are
wavelength, laser beam energy and number of pulses. The numerical 3D model of the generated heat on the
silver coated copper plate was obtained using the COMSOL Multiphysics software package and was carried
out with the aim to define the temperature distribution around the irradiated zone and the maximum
temperatures.
Optical microscopy, SEM and EDX analysis are used for the diagnosis of the morphological and chemical
effects of laser irradiation on real sample surface. Obtained results are compared with results of laser
irradiation analyses on naturally tarnished metal yarns embroidery from museum sample.
This investigation confirms that Nd:YAG lasers can be successfully used for metal yarns cleaning. Application
of adequate numerical model can provide an opportunity for a faster and cheaper determination of the cleaning
process optimum values range. Some parameters for successfully and safely cleaning of silver coated
copper surface were determined. | sr |