Using lasers for cleaning ceramic and plaster patrimonial objects

International audienceTraditional cleaning techniques (sandblasting, chemical, ...) turn out to be ineffective or damaging on some ceramics and plaster objects. It's especially true on outdoor ceramics covered with black crust or indoor biscuits wares and plasters exposed to dust and repeated handling. The use of lasers to remove dirt, such as for stone, has then been considered. This paper study the behavior of these materials under the impact of different type of lasers irradiation (Nd:YAG first and third harmonic, excimer,...). According to the type of dirt and underlying material, the effectiveness of cleaning depends on the laser wavelength and its energy density. The results are satisfactory with no damage and no coloration change on plaster cleaning by Nd:YAG third harmoni

Lasers Cleaning of Patrimonial Plasters

International audienceThe use of the lasers Q-switched Nd:YAG to remove the dust of the stone monuments especially sculpture gradually replaces the more abrasive technique of sandblasting. This tendency made us consider the lasers as solution for the cleaning of ceramics and the plasters. Indeed in museums, these materials are often covered with dirty mark (dust, grease, etc.) which is difficult to remove without damaging the object. This paper deals with the impact of different types of lasers (Nd:YAG first and third harmonic) irradiation on plaster and with the effects on its morphology and its crystallography. Plaster is an interesting material because of its typical acicular crystals altered at low temperature. That is why synthesis samples were prepared, constrained in temperature then analysed by various processes (SEM, XRD, TGA. . . ). These results were compared with samples cleaned by laser. That enabled us to conclude that plasters cleaned by UV-laser (third harmonic of the Nd:YAG) underwent neither yellowing, nor morphological or crystallographic changes. It has to be opposed to the intense yellowing, and sometimes morphological destruction, which appears with an infrared wavelength (first harmonic of the Nd:YAG)

Cathodic electrochemical detection of sonochemical radical products

This paper reports on an electrochemical technique for the detection of oxidizing radical species, produced as the result of cavitation induced by ultrasound. A study of two example reactions is reported: the Weissler reaction and the Fricke reaction. In both cases, redox-active materials trap oxidative radicals. Electrochemical detection within a flow cell system is then used to sense redox-active products of the reactions between a chosen trapping agent and radicals produced within an ultrasonically irradiated aqueous solution. A demonstration of the sensitivity of electrochemical detection of radical products is presented. An equivalent dose of the ultrasonic reactor is reported

The ‘Historiated’ Neolithic Stele of Saint-Samson-sur-Rance (Côtes-d'Armor, France)

International audienc