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Silver artefacts and particularly ancient silver artefacts present the serious problem of the black look due to ambient contamination. The black colour is the consequence of the layer forming on the surface made of acanthite and jalpaite, both compounds are sulphur composts. Recently UV laser cleaning technique has demonstrated to be very promising in processing of cultural artefacts. To operate on artefacts without to contaminate the bulk, first we determined the laser fluence threshold of the bulk, second we controlled the surface compounds and at the end we operated the laser irradiation. In this work we utilised certified silver and silver/copper samples in order to perform preliminary studies. The threshold fluence we found were 780 and 510 mJ/cm2 for the Ag pure and for the Ag/Cu alloy, respectively. The jalpaite concentration on Ag/Cu sample increased after the laser dose of 25 J/cm2, while for higher laser dose its value lowered pointing out that complex processes take part during the laser application. As a successful of our studies we applied the technique on a Carlino coin made of silver coined in 1689 under King Carlo II. The analyses were performed by two different techniques able to find the percentage of elements and the chemical compounds; the EDXRF and the XRD. We found that the sulphur concentration decreased on laser dose. Operating on the coin up to a dose of 280 J/cm2 the sulphur concentration deceases up to 20 %, while the coin look becomes clear just after a 50 J/cm2.

In this paper we report the experimental results of the study of evaluation of an UV laser cleaning treatment on a bronze bell outdoor, dating from the second half of the 600. Energy dispersive X-ray fluorescence (EDXRF) non-destructive analysis was performed on the bell before, during and after the cleaning treatment in order to assess the laser ablation threshold, to define the efficiency of laser cleaning process, to avoid possible damage of laser on the bell, to determine the concentration of the constituents of both the patina and the alloy. In particular, an EDXRF portable apparatus was used in order to evaluate the variation of concentration of sulfur, chlorine, calcium, copper, lead and tin during the laser cleaning.

Energy-dispersive X-ray fluorescence (EDXRF) portable spectrometers are becoming very popular in many fields for the on-site analysis of elements. This is mainly because EDXRF is a nondestructive, multielemental technique that is extremely well suited for the analysis of any material. An EDXRF spectrometer mainly consists of an X- or γ-ray excitation source, an X-ray detector with electronics, and a pulse-height analyzer. Recent technological developments have resulted in small, low-power, dedicated X-ray tubes, thermoelectrically cooled semiconductor detectors, and small pulse-height analyzers. Therefore, completely portable EDXRF spectrometers are available that can be assembled on-site, having the size of a book and a weight ranging from as light as 500 g (using a radioactive source) to a few kilograms (using an X-ray tube). These spectrometers can be employed for on-site analysis in various fields, such as works of art, alloys, soil, environmental samples, forensic medicine, paper, waste materials, mineral ores and their products, or anywhere a portable apparatus would be required. This article reviews the present status of the development and application of EDXRF portable systems. The various components of a portable system are described: the radiation source, i.e. small, low-power, dedicated X-ray tubes or, alternatively, radioactive sources that emit X-rays or low-energy γ-rays; and X-ray detectors, i.e. proportional gas counters and semiconductor detectors, with special emphasis on the more recent thermoelectrically cooled X-ray detectors: Si-PIN (Positive-Intrinsic-Negative), Si-drift, CdTe, CdZnTe, HgI2, and others. Commercial systems are considered, and finally the most common and significant applications are described, with particular emphasis to the field of works of art.

Results about the efficiency of the laser cleaning on the reduction of corrosion products from the surface of ancient coins are reported. In this work an ancient copper coin datable from 1500 to 1600 A.D. and a UV excimer laser were utilized. The goal of this work consists to study the potentiality of UV laser treatment in the reduction of the chlorine concentration on the coin surface which is the main responsible of the corrosion processes of the ancient coins. We used Energy Dispersive X-Ray Fluorescence (EDXRF) and X-Ray Diffraction (XRD) techniques to estimate the chemical composition of the coin surface, before and after UV excimer laser cleaning. In particular, we measured the chlorine, copper and calcium concentrations. We found that a radiation dose of about 19 J/cm 2 was able to reduce the chlorine concentration from 2.3 % w/w to 0.6 % w/w without damaging the metal bulk. Keywords: ancient coins; patina ; copper chlorides; laser cleaning; EDXRF portable apparatus

The present work has the purpose to evaluate experimentally the ablation threshold fluences of copper, silver, and their alloys in order to induce a safety laser cleaning of the metal artifacts avoiding damages to the bulk. We used two different pulsed lasers: a KrF excimer laser operating at 248 nm, 23 ns pulse duration and a Nd:YAG laser operating at 532 nm (second harmonic), 3 ns pulse. Preliminary experimental results about the laser cleaning of bronze coins will be reported. The laser cleaning consists on the reduction of the chlorine concentration from the surface of the coins. The laser cleaning, carried out by the KrF laser, provides a safe way of removing the chlorine concentration as the Energy Dispersive X-Ray Fluorescence analyses will demonstrate.

Portable energy-dispersive X-ray fluorescence (EDXRF) spectrometers are becoming very popular in many fields for the on-site analysis of elements. This is mainly because EDXRF is a nondestructive, multielemental technique that is extremely well suited for the analysis of any material. An EDXRF spectrometer mainly consists of an X- or γ-ray excitation source, an X-ray detector with electronics, and a pulse height analyzer. Recent technological developments have resulted in small, low-power, dedicated X-ray tubes, thermoelectrically cooled semiconductor detectors, and small pulse height analyzers. Therefore, completely portable EDXRF spectrometers are available that can be assembled on-site, having the size of a book and a weight ranging from as light as 500 g (using a radioactive source) to a few kilograms (using an X-ray tube). These spectrometers can be employed for on-site analysis in various fields, such as works of art, alloys, soil, environmental samples, forensic medicine, paper, waster materials, mineral ores and their products, or anywhere a portable apparatus would be required. This paper reviews the present status of the development and application of EDXRF portable systems. The various components of a portable system are described: the radiation source, i.e. small, low-power, dedicated X-ray tubes or alternatively radioactive sources that emit X-rays or low-energy γ-rays; and X-ray detectors, i.e. scintillators, proportional gas counters and semiconductor detectors, with special emphasis on the recent thermoelectrically cooled X-ray detectors: Si-PIN (silicon positive–intrinsic– negative), Si-strip and CZT (cadmium–zinc–telluride). Commercial systems are considered, and finally the most common and significant applications are described.

In this work we report the preliminary experimental results on the selective ablation of sulphur in ancient stones. The sulphur concentration was reduced after laser action. For this goal an excimer laser operating at 308 nm wavelength and time duration of 20 ns was used. In order to estimate the sulphur concentration before and after laser cleaning, a portable apparatus for energy-dispersive X-ray fluorescence (EDXRF) was utilised. The processed sample were characterized by an initial sulphur concentration of 2.8% w/w. After the laser treatment, sulphur concentration decreased after a total deposited energy of about 30 J/cm 2 up to 1.2% w/w value. Due to the porosity of the stone, in fact, it is difficult to eliminate completely the S presence in the composition of the stones. It was also observed that after a few laser shots the initial black area of the stone became white showing in this way the great potential of the laser action on the cleaning process of the pietra leccese.

In this work we determined experimentally the threshold fluence of the most common metals found in cultural heritage, e.g. copper, silver and their alloys. We carried out the ablation process in air at atmospheric pressure with 8 ns pulsed Nd:YAG and 23 ns pulsed KrF lasers, at 532 and 248 nm, respectively. We irradiated every target by a fixed number of laser shots (repetition rate of 1 Hz) at several laser fluence values. Then, the resulting craters were characterized by a stylus surface profiler in order to obtain the dependence of ablation rate on laser fluence F. Here, we defined the ablation raate as ablated matter thickness for single laser pulse, x. Therefore, we identified the ablation threshold fluence, Fth, as the fluence value below which no ablation process would occur.