Evaluation of laser cleaning for the restoration of tarnished silver artifacts

Abstract

a b s t r a c tIn this study we evaluate the laser cleaning of tarnished pure and sterling silver substrates using a nanosecond Q-switched Nd:YAG laser at 1064, 532 and 266 nm. To assess the effects associated with cyclic laser cleaning treatments, several cycles of tarnishing followed by laser cleaning were applied on silver coupons that were characterized by gravimetry, colorimetry, scanning electron microscopy, X-ray photoelectron spectroscopy and micro-Raman spectroscopy. According to the obtained results, none of the three wavelengths is recommended for laser cleaning of pure silver objects, while for sterling silver artifacts, the visible laser wavelength of 532 nm seems the most appropriate.

Procedimentos de limpeza aplicados na conservação de ladrilhos de marmorite do início do século XX

“…Estudos mostram que longos pulsos induzem alteração nos objetos -nos metais, por exemplo, causa fusão -, enquanto pulsos curtos são preferíveis (PINI et al, 2000). O tratamento a laser, com irradiação a 1.064 nm, causa grandes perdas de massa em granitos (POZO-ANTONIO et al, 2016) e alteração de cor em objetos metálicos (PALOMAR et al, 2016), fato corroborado pelas alterações de brilho observadas.…”

The research progress on corrosion and protection of silver layer

“…The analysis and characterization of the Ag discoloration part and corrosion layer mainly includes: Based on the analysis of discoloration site and corrosion layer of Ag objects, the scientists and technicians have developed the corresponding cleaning methods to recover the appearance and performance of corroded Ag, which includes: mechanical cleanings [19,20], chemical cleanings [19][20][21] (sodium glycinate, thiourea acid solution, thiosulphate solution, formic acid, alcohol, surfactant, acetone, et al), electrochemical cleanings [22,23] (constant current cathodic reduction, electrolytic pencil), laser cleanings [24][25][26][27] [Q-switched Nd: YAG laser, emitting infrared (1064 μm), visible (532 nm) and ultraviolent (355 nm) radiation], Ar ions irradiation cleanings [28], Ar plasma cleanings [29,30], plasma afterglows cleanings [31], UV/Ozone cleanings [32], and so forth. The characteristics of various cleaning methods are also pointed out.…”

Investigation on the Surface Properties of 5A12 Aluminum Alloy after Nd: YAG Laser Cleaning

“…Takahashi et al [11] proposed a new concept of laser-assisted material removal that uses laser-assisted ultraviolet radiation to achieve nanoscale correction of microscopic three-dimensional (3D) objects. Palomar et al [12] used a nanosecond Q-switched Nd: YAG laser to remove dirt from pure silver products, and then determined the optimal cleaning threshold of pure silver cultural relics. Delaporte et al [13] used a Nd: YAG laser (6 ns) and a xenon flash lamp (200 ms) for dust removal of radioactive compounds.…”