Stabilization of verdigris pigment on paper : evaluation of antioxidants under mild accelerated degradation conditions

Malešič, Jasna (author), Retko, Klara (author), Finšgar, Matjaž (author), Kralj Cigić, Irena (author)

Copper-based pigments, such as verdigris, have caused severe damage to many important historical documents, and their preservation remains a significant concern for paper conservators and researchers. This study re-evaluates the efficacy of two promising antioxidants, tetrabutylammonium bromide (TBABr) and benzotriazole (BTA), as stabilization agents for paper documents containing verdigris pigment. The evaluation was conducted under mild accelerated degradation conditions using historically accurate mock-up paper samples. To assess the stability of the mock-up papers, various parameters were measured during accelerated degradation, including colour, molecular weight (Mw), and pH value. Size exclusion chromatography measurements of Mw confirmed that TBABr provided superior stabilization compared to BTA. Additionally, the total colour change was slightly more pronounced in the samples treated with BTA compared to those treated with TBABr. However, during degradation, some paper samples containing thicker application of pigment exhibited significant black and brown spots, regardless of treatment (untreated, treated with BTA, or TBABr). X-ray photoelectron spectroscopy confirmed the presence of both Cu(I) and Cu(II) oxidation states in all samples, with a higher Cu(II) content on the surface of TBABr treated samples compared to those treated with BTA. This may indicate differences in the mechanisms of degradation. Raman spectroscopy identified the spots on both untreated and TBABr-treated samples as copper(II) oxide.

• Language: English
• Keywords: verdigris, degradation, paper, stabilization, antioxidants
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 12 str.
• Numbering: Vol. 90, iss. 5, art. e202400670
• PID: 20.500.12556/RUL-168919
• UDC: 7.025.3/.4:691.14
• ISSN on article: 2192-6506
• DOI: 10.1002/cplu.202400670
• COBISS.SI-ID: 226885635
• Publication date in RUL: 28.05.2025

Record is a part of a journal

• Title: ChemPlusChem
• Shortened title: ChemPlusChem
• Publisher: Wiley, Chemistry Europe
• ISSN: 2192-6506
• COBISS.SI-ID: 2732539

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.

Secondary language

• Language: Slovenian
• Keywords: verdigris, papir, razgradnja, stabilizacija, antioksidanti, ohranjanje dokumentov