Synthesis of Copper Pigments, Malachite and Verdigris: Making Tempera Paint

Abstract

A ll paints contain pigment, which provides color, and a binder (or medium), which suspends the pigments and binds them to the surface of the object to be painted. Two paint pigments, malachite and verdigris, are synthesized in this general chemistry laboratory experiment and then a tempera paint is made using malachite. While introducing the students to the composition of artists' paints, performing this experiment exposes students to chemical concepts such as stoichiometry (excess reactants and yields), solubility, precipitation, and properties of emulsions.Copper sulfate is the starting material for the one-step synthesis of malachite and the three-step synthesis of verdigris. Both syntheses can be done with a magnetic stir plate, standard glassware, and chemicals purchased from hardware stores and supermarkets. The products are dried and weighed to determine percent yields. Malachite pigment is combined with egg yolk binder to make tempera paint. A version of the student write-up for this experiment can be found in a laboratory manual that contains standard first-year general chemistry experiments, all of which can be done with household chemicals. 1 The experiment was tested by students enrolled in a general chemistry course. Knowing they would be required to finish both syntheses in one lab period was a strong motivation for students to read the experiment before coming to class to devise timesaving strategies. Results obtained from the class include time required to finish both syntheses, yields of both pigments, as well as the ideas used by students to make best use of their time.This experiment can also be used to explore green chemistry. Among the principles to classify a reaction as "green" are the use of nonhazardous starting materials, their maximum incorporation into products, use of ambient temperature for energy efficiency, and production of nontoxic products. The malachite dx.

Wall paintings through the ages: the medieval period (Italy, twelfth to fifteenth century)

“…Other colours could not withstand the alkaline environment of the lime, and were therefore more often used in a secco paint, bound in organic media as egg or oil. The range includes a few organic pigments (Aceto 2021) and some inorganic pigments such as lead white, a basic lead carbonate, and red lead (Gonzalez et al 2016;Gliozzo and Ionescu 2021); arsenic-based pigments such as realgar and orpiment (Gliozzo and Burgio 2021); cinnabar, a mercury sulphide which is bright red, and could be mixed with white to give a pink flesh colour (Thompson jr 1933;Spring and Grout 2002;Gliozzo 2021); ultramarine, an expensive blue pigment prepared from the mineral lapis lazuli (Gaetani et al 2004;Osticioli et al 2009;Favaro et al 2012); azurite, a natural blue pigment cheaper than ultramarine, obtained by this copper carbonate hydroxide natural mineral (Dei 1998;Bucklow 2013;Švarcová et al 2021); malachite, a pigment obtained from this natural green copper carbonate hydroxide, which was sometimes also used in a fresco paint without organic binders (Solomon et al 2011;Švarcová et al 2021).…”

Characterizing Color with Reflectance

“…A set of paint swatches collected by a student is shown in Figure 2. At least two papers in this Journal describe students making paints from artists' pigments in a traditional general-chemistry course (malachite and verdigris) 22 and in a novel multidisciplinary general-chemistry course (Egyptian blue). 23…”

From Test Tube to Turner – the Role of the Chemist in Art

“…A similar process was developed for the production of verdigris (the green of Greece) (basic copper acetate) 10,11 . This same principle of using an acid to dissolve a metal or metal oxide and then using a base to precipitate it is the sample principle as that used below for other inorganic pigments but they needed stronger acids.…”