Laser ablation-ICP-MS depth profiling to study ancient glass surface degradation

Area of Science:

• Archaeometry
• Materials Science
• Analytical Chemistry

Background:

• Archaeological glass analysis is hindered by surface weathering and corrosion.
• Accurate elemental analysis requires penetrating these alteration layers, often exceeding 10 μm.
• Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a key technique for elemental analysis.

Purpose of the Study:

• To investigate the chemical and physical changes in ancient glass alteration layers.
• To assess the effectiveness of laser drilling for analyzing weathered glass.
• To correlate elemental composition changes with glass degradation.

Main Methods:

• Laser drilling in two modes (1 Hz and 10 Hz) for controlled material removal.
• Inductively coupled plasma-mass spectrometry (ICP-MS) for elemental quantification.
• Sum normalization calibration protocol for quantitative depth profiling (wt%).
• Profilometry for measuring depth and material removal via laser shots.

Main Results:

• Detailed elemental depth profiles (ca. 20 elements to 5 μm; 50-60 elements to 50 μm) were obtained.
• Increased SiO2 (wt%) in the alteration layer correlates with Na2O and K2O depletion.
• Laser drilling parameters directly influence depth and spatial resolution of analysis.
• Chemical and physical changes were measured in four ancient glass artifacts.

Conclusions:

• Laser drilling coupled with ICP-MS is effective for analyzing ancient glass weathering.
• Elemental changes, particularly alkali depletion, drive alterations in glass structure and density.
• Understanding these changes provides insights into glass artifact preservation and degradation factors.