Issue 45, 2016

Characterization and utilization of Prussian blue and its pigments

Abstract

This review deals with our long-range goal of determining why the Prussian blue pigments, typically either the “soluble” KFeIII[FeII(CN)6xH2O or the alternative “insoluble” FeIII4[FeII(CN)6]3·xH2O compounds, used by artists from shortly after the discovery of Prussian blue in 1704 and well into the early twentieth century, often fade when exposed to light. In order to achieve this goal it was decided that first, for comparison purposes, we had to prepare and fully characterize Prussian blues prepared by various, often commercially successful, synthetic methods. The characterization has employed a large variety of modern methods to determine both the stoichiometry of the Prussian blues and the arrangement of the voids found in the latter “insoluble” Prussian blues. The refinement of synchrotron radiation derived X-ray powder diffraction data obtained for a formally soluble and an insoluble Prussian blue required refinement in the Pm[3 with combining macron]m space group and lead to the K1.9[FeIII4FeII3(CN)18]·{1.9 OH + 7.0H2O}, 1, and FeIII4FeII3(CN)18·11.0H2O, 2, stoichiometries. The former compound, 1, exhibits an apparently random iron(II) long-range void arrangement, whereas 2 exhibits a more non-random long-range arrangement, however, a pair distribution function analysis indicates a short-range ordering of the voids in both compounds. After further detailed characterization of many Prussian blue samples, painted samples on linen canvas, were subjected to accelerated light exposure for up to 800 hours either as pure Prussian blues or mixed with (PbCO3)2Pb(OH)2, ZnO or TiO2, the white pigments often used by artists to lighten the intense Prussian blue colour. The results indicate that the first two of these white pigments play a significant role in the fading of the colour of Prussian blues. In order to achieve our long-range goal, several Prussian blue samples were prepared from “ancient” recipes published in 1758 and 1779. These so-called “ancient” samples, painted in a dark and a pale blue shade, were also subjected to accelerated light exposure. The colorimetric results, in conjunction with X-ray powder diffraction refinements, pair distribution analysis and Mössbauer spectral results, indicate that, depending on the exact method of ancient preparation, the Prussian blue pigments were sometimes badly contaminated with alumina hydrate and/or ferrihydrite, a contamination which leads to extensive fading or decolourization of the Prussian blue pigments. The presence of ferrihydrite was subsequently confirmed in the study of a surface paint fragment from an eighteenth-century polychrome sculpture.

Graphical abstract: Characterization and utilization of Prussian blue and its pigments

Supplementary files

Article information

Article type
Perspective
Submitted
26 Aug 2016
Accepted
22 Oct 2016
First published
24 Oct 2016

Dalton Trans., 2016,45, 18018-18044

Characterization and utilization of Prussian blue and its pigments

F. Grandjean, L. Samain and G. J. Long, Dalton Trans., 2016, 45, 18018 DOI: 10.1039/C6DT03351B

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements