Laser ablation cleaning of an underwater archaeological bronze spectacle plate from the H.M.S. DeBraak shipwreck

Bartosz A. Dajnowski

doi:10.1117/12.2022526

30 May 2013 Laser ablation cleaning of an underwater archaeological bronze spectacle plate from the H.M.S. DeBraak shipwreck

Bartosz A. Dajnowski

Author Affiliations +

Proceedings Volume 8790, Optics for Arts, Architecture, and Archaeology IV; 87901K (2013) https://doi.org/10.1117/12.2022526
Event: SPIE Optical Metrology 2013, 2013, Munich, Germany

Abstract

Laser ablation was successfully used to sequentially remove layers of concretion and corrosion from the surface of a copper alloy spectacle plate from the shipwreck of His Majesty’s Sloop of War DeBraak. The H.M.S. DeBraak was a single-masted cutter that was originally a Dutch ship until it was taken by the British, refitted, and repurposed as a Royal Navy ship in 1796. The ship sank along the Delaware coast in 1798 and artifacts were recovered from the wreck site in 1984. This spectacle plate is an important part of the ships rudder and it is part of the collection of the Delaware Division of Historical and Cultural Affairs. The object was brought the Winterthur/University of Delaware Program in Art Conservation for treatment. The object was examined with cross section microscopy, Raman spectroscopy, X-ray fluorescence spectroscopy (XRF), and Energy Dispersive Spectroscopy (EDS) as well as Back Scattered Electron (BSE) analysis with a Scanning Electron Microscopy (SEM). Interestingly, layers of both copper and iron corrosion products were identified within the concretion. A 1064nm Long Q-Switch (LQS) laser with 100ns pulses was tested along with a Short Free Running (SFR) with 60 - 130 microseconds pulses, at various fluences and frequencies, to determine optimal cleaning parameters for removing the concretion. Laser cleaning also revealed fragments of wood from the original rudder, which were previously trapped within the concretion. After laser cleaning, the spectacle plate was treated with 3% Benzotriazole in ethanol and then given a protective microcrystalline wax coating.

Citation Download Citation

Bartosz A. Dajnowski "Laser ablation cleaning of an underwater archaeological bronze spectacle plate from the H.M.S. DeBraak shipwreck", Proc. SPIE 8790, Optics for Arts, Architecture, and Archaeology IV, 87901K (30 May 2013); https://doi.org/10.1117/12.2022526

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