Finnish wallpaper pigments in the 18th–19th century: Presence of KFe3(CrO4)2(OH)6 and odd pigment mixtures

Several Finish wallpapers from the 18th and 19th century were analysed by using Raman spectroscopy assisted with EDXRF instrumentation, in an attempt of determine the pigments used in their manufacture process as well as of trying to date some of the samples through pigment composition. All pigments present in samples were determined and surprisingly the unusual and strange iron (III) chromate yellow pigment was found. Besides, unusual mixtures were found to obtain fashionable colours, especially in blue and green areas, where more than one blue pigments were mixed with green and yellow pigments. Blue verditer, ultramarine blue, Prussian blue, chrome yellow, calcite, lead white, red and yellow iron oxide, gypsum and carbon black were identified. The presence of the risky and poisonous emerald green must be highlighted. The results were compared with those found in other wallpapers from Spain and France.

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► Decorated wallpapers dating from the 18th and 19th century were analysed.
► Yellow iron (III) chromate (KFe3(CrO4)2(OH)6), a very strange pigment was found.
► Unusual and odd mixtures were found to obtain fashionable colours.
► The presence of the poisonous emerald green (Cu(C2H3O2)2⋅3Cu(AsO2)2) is described.