X-ray Fluorescence and Colorimetry Data of Vermilion (HgS) Degradation Induced by Hypochlorite and UV Light

Description

The dataset presented analyzes mockup samples replicating oil canvases painted by Cristóbal Lozano, an XVIII-century Peruvian artist. These samples were exposed to sodium hypochlorite (bleach) and UV-A light to simulate degradation caused by household cleaning products on oil paintings using vermilion (HgS) as the red pigment.

Steps to reproduce

1. Preparation of Mockup Samples: Vermilion with 99% purity (α-HgS, Sigma-Aldrich®) was used. Samples were prepared on Belgian linen cloth with a plain weave (24 weft by 18 warp threads), cut into 30 mm x 10 mm x 1 mm pieces. A ground layer of calcium carbonate and Cervione animal glue was applied, followed by a second layer of vermilion and linseed oil (VanDyck®) in a 3:2 ratio. 2. Degradation Testing: Linen samples were suspended inside 6.4 cm x 1.5 cm glass containers with 3 mL of commercial bleach (7.5% v/v NaClO). Samples were exposed to UV-A light (399 nm wavelength) in a controlled chamber (Figure 2A), arranged between two UV-A lamps. A control group remained in darkness, with containers covered in aluminum foil. UV-A was selected for its ability to penetrate glass. 3. Data Collection: Over 30 days, data were collected at 0, 1, 3, 6, 10, 20, and 30 days. The UV-A lamp raised the linen temperature to 31°C, with an average relative humidity of 82%. A PCE-XXM 30 wireless instrument measured red color intensity by analyzing the absorption spectrum (baseline intensity at ~500 nm vs. signal intensity at ~700 nm for red wavelengths). Lab color space measurements (L: lightness, a: green/red, b*: yellow/blue) were also performed. Elemental analysis using portable X-Ray Fluorescence (pXRF, Hitachi X-MET 8000 Expert) detected high atomic number elements in alloy mode, with a measurement time of 20 seconds per sample. Colorimetry and pXRF analyses were conducted after each exposure interval.

Institutions

• Universidad de Ingenieria y Tecnologia

Categories

Funders

• Prociencia - CONCYTEC

  Grant ID: 035-2019-FONDECYT-BM

Licence