Colour changes by laser irradiation of reddish building limestones

Grossi Sampedro, Carlota and Benavente, David (2016) Colour changes by laser irradiation of reddish building limestones. Applied Surface Science, 384. pp. 525-529.

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Abstract

We have used X-ray photoelectron spectroscopy (XPS) as a novel method to investigate the causes of colour changes in a reddish limestone under irradiation by a Q-switched Nd:YAG 1064 nm laser. We irradiated clean dry and wet surfaces of Pidramuelle Roja, a building stone frequently used in the Asturian heritage, at fluences ranging from 0.12 to 1.47 J cm−2. We measured the colour coordinates and undertook XPS analysis of the state of oxidation of iron both before and after irradiation. Visible colour changes and potential aesthetic damage occurred on dry surfaces from a fluence of 0.31 J cm−2, with the stone showing a greening effect and very intense darkening. The colour change on dry surfaces was considerably higher than on wet surfaces, which at the highest fluence (1.47 J cm−2) was also above the human visual detection threshold. The use of XPS demonstrated that the change in colour (chroma and hue) is associated with a reduction in the iron oxidation state on dry surfaces during laser irradiation. This points out to a potential routinary use of XPS to analyse causes of colour changes during laser cleaning in other types of coloured building stones.

Item Type: Article
Uncontrolled Keywords: q-switched nd:yag 1064 nm laser,heritage red limestones,x-ray photoelectron spectroscopy,iron oxidation state,colour variation
Faculty \ School: Faculty of Medicine and Health Sciences > School of Health Sciences
Depositing User: Pure Connector
Date Deposited: 02 Jun 2016 11:01
Last Modified: 10 Jun 2020 23:58
URI: https://ueaeprints.uea.ac.uk/id/eprint/59193
DOI: 10.1016/j.apsusc.2016.05.031

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