Identification of Pre-1950 Synthetic Organic Pigments in Artists’ Paints. A Non-Invasive Approach Using Handheld Raman Spectroscopy

Rika Pause,Inez Dorothé Van Der Werf,Klaas Jan Van Den Berg

doi:10.3390/heritage4030073

Rika Pause, Inez Dorothé Van Der Werf + Show 1 more

Open Access

https://doi.org/10.3390/heritage4030073

Copy DOI

Journal: Heritage	Publication Date: Jul 17, 2021
Citations: 11	License type: CC BY 4.0

Affiliation: Cultural Heritage Agency of Netherlands

Abstract

There is little information on the actual use of early synthetic organic pigments (SOPs) in art objects, especially those from before 1950. Their presence can, however, pose a challenge to conservation because their chemical composition, as well as their lightfastness and sensitivity to solvents, are often unknown. Here, a study on the non-invasive identification of SOPs in historic pre-1950 varnished paint-outs from artists’ materials manufacturer Royal Talens is presented. The paints were analysed using a handheld Raman device. Spectra were evaluated by recording the spectra of the same samples with a benchtop instrument. This study demonstrated that the identification of SOPs in varnished oil paints with a non-invasive approach is possible and rather straightforward. The handheld Raman device allowed us to identify fourteen SOPs from eight pigment classes. Besides the occurrence of expected and the known SOPs of this time period, there were also some surprising results, like the detection of the triarylcarbonium pigments PG2 and PB8, and the monoazo Mordant Yellow 1.

Highlights

IntroductionAfter the accidental discovery of mauveine in 1856, a new class of dyestuffs and pigments was developed and introduced to the market
After the accidental discovery of mauveine in 1856, a new class of dyestuffs and pigments was developed and introduced to the market. These were formerly defined as coal-tar dyes and are nowadays called synthetic organic pigments (SOPs)
In contrast to natural organic pigments, they are synthesized in a laboratory environment and produced on an industrial scale, so that natural organic pigments like indigo and alizarin can be considered as SOPs when they are produced industrially [1]

Summary

Introduction

After the accidental discovery of mauveine in 1856, a new class of dyestuffs and pigments was developed and introduced to the market. In contrast to natural organic pigments, they are synthesized in a laboratory environment and produced on an industrial scale, so that natural organic pigments like indigo and alizarin can be considered as SOPs when they are produced industrially [1]. After their introduction, paint manufacturers started to use SOPs for their tube paints, which led to new shades in artists’ colours and to the imitation of traditional pigments [2,3,4].

Objectives

Methods

Results