Pigments—the palette of organic colourants in wall paintings

Abstract

The present contribution deals with the use of organic colourants in wall paintings, polychrome pottery and painted stone artworks, i.e. painted artworks on inorganic supports. The term organic colourants is referred to the chemical nature of these compounds but not to the way of application; therefore, organic colourants can be dyes, lakes or pigments. The use of organic colourants in wall paintings has been given little attention in the past, perhaps on the assumption that they were rarely used by ancient artists. Recent diagnostic studies, however, brought evidence that their use was not fragmentary; on the contrary, there seems to be continuity in the centuries, at least with regard to the most widely used such as madder, Tyrian purple and indigo. Sources, alteration phenomena, identification methods and analytical evidence is given for the main organic colourants with concern to red, yellow, green, purple and blue hues. Drawbacks and issues are discussed with concern to the identification techniques.

Wall paintings through the ages: the roman period—Republic and early Empire

“…The so-called first style or "incrustation style" in Roman painting, documented from the middle of the second century BC, is usually interpreted as an "Italic version" of the socalled masonry style or Greek masonry style (Hinks 1933;Bruno 1969). This aims at reproducing using painted plaster and stucco the architectural elements and ornamental features of the opus quadratum-what suggests a clear inspiration by the construction models of the classical period.…”

“…This new approach revitalised the studies in Roman painting, leading to an increase in the number of publications in the following decades (e.g. Abdal Casal 1982 for Spain) It impacted also on the centennial studies in Roman wall paintings in the Vesuvian area, which began to focus on the production process and to understand it as artisanal manufacturing only from the 1990s onwards.…”

Production, transport and on-site organisation of Roman mortars and plasters

“…Three archaeological reviews on prehistoric (Domingo Sanz and Chieli 2021), Roman (Salvadori and Sbrolli 2021) and Mediaeval (Murat 2021) wall paintings clarify the archaeological and historical/cultural framework. A series of archaeometric reviews illustrate the state of the art of the studies carried out on Fe-based red, yellow and brown ochres (Mastrotheodoros et al 2021); Cu-based greens and blues (Švarcová et al 2021); As-based yellows and reds (Gliozzo and Burgio 2021); Pb-based whites, reds, yellows and oranges (Gliozzo and Ionescu 2021); Hg-based red and white (Gliozzo 2021) and organic pigments (Aceto 2021). An overview of the use of inks, pigments and dyes in manuscripts, their scientific examination and analysis protocol (Burgio 2021) as well as an overview of glassbased pigments (Cavallo and Riccardi 2021) are also presented.…”

Mortars, plasters and pigments—research questions and sampling criteria

“…Three archaeological reviews on prehistoric (Domingo Sanz and Chieli 2021), Roman (Salvadori and Sbrolli 2021) and Medieval (Murat 2021) wall paintings clarify the archaeological and historical/cultural framework. A series of archaeometric reviews illustrate the state of the art of the studies carried out on Fe-based red, yellow and brown ochres (Mastrotheodoros et al forthcoming); Cu-based greens and blues (Švarcová et al 2021); As-based yellows and reds (Gliozzo and Burgio 2021); Pb-based whites, reds, yellows and oranges (Gliozzo and Ionescu 2021); Hg-based red and white (Gliozzo 2021); and organic pigments (Aceto 2021). An overview of the use of inks, pigments and dyes in manuscripts, their scientific examination and analysis protocol (Burgio 2021) as well as an overview of glass-based pigments (Cavallo and Riccardi forthcoming) is also presented.…”

“…Moreover, while the recipe's reconstruction mostly regards the technological issue, the end-use of a mortar provides the necessary link to establish its suitability and functionality. Basically, there Table 1 Definitions and uses of pigment, ink, dye and de/colouring agents to be used in archaeometry * For a review on organic colouring materials used in wall painting, see Aceto (2021) in this TC ** The term lac may refer to two very different types of inorganic compounds: a) the gommalacca or shellac, i.e. "a pink-red-purple organic colourant derived from an insect and used as a lake pigment or a dye" (Berbers et al 2019); b) a mixture of nitrocellulose and resin/wax Glass are two types of mortars: the aerial (Ergenç et al 2021 in this TC) and the hydraulic ones (Arizzi and Cultrone 2021 in this TC).…”