Physicochemical investigation of blackening process of rock art pigment in Leang Lompoa (Pangkep Regency, South Sulawesi, Indonesia)
Moh. Mualliful Ilmi (a*), Grandprix Thomryes Marth Kadja (b,c), Pindi Setiawan (d), Djulia Onggo (b), Ismunandar (b)

a) Chemistry Laboratory, Department of Pharmacy, Universitas Nahdlatul Ulama Sunan Giri Bojonegoro, Jl. A Yani no. 10, Bojonegoro 62115, Indonesia
*ilmi.kimia[at]gmail.com
b) Division of Inorganic and Physical Chemistry, Institut Teknologi Bandung, Jl. Ganesha no. 10, Bandung 40132, Indonesia
c) Research Center for Nanosciences and Nanotechnology, Institut Teknologi Bandung, Jl. Ganesha No. 10, Bandung 40132, Indonesia
d) Division of Visual Communication and Multimedia, Institut Teknologi Bandung, Jl. Ganesha no. 10, Bandung 40132, Indonesia

Abstract

The color change process is among the various threats endangering the preservation of the Maros-Pangkep rock art. Among the rock art sites in the Maros-Pangkep Region experiencing the color change of rock art pigments is Leang Lompoa. The color change process is indicated the presence of black deposits covering several hand stencils images. In this work, we aim to investigate the blackening process in rock art in Leang Lompoa by studying the physicochemical properties of the pigment. Here, we employed a combined multi-analytical characterization, including optical microscopy observation, elemental analyzes of X-ray fluorescence (XRF), scanning electron microscopy coupled with energy dispersive electron spectroscopy (SEM-EDS), and Raman spectroscopy. The result indicates that the blackening process of the rock art of Leang Lompoa was due to the formation of black deposit made up charcoal. It was confirmed by by the presence of peaks of D and G Bands at Raman shifts of 1326 cm-1 and 1598 cm-1. Charcoal deposits can originate from the accumulation of soot generated by anthropogenic activities around the site. In addition, the deposit may also have formed due to an accidental fire on a haystack on the site, where the Leang Lompoa site is now used as a hay storage area by the local population.

Keywords: Rock art, burning, black deposit, Leang Lompoa, Pangkep, Indonesia

Topic: CHEMISTRY AND MATERIAL SCIENCES