Verdigris
Composition and Properties of Verdigris
Verdigris is not a unique chemical substance but is a collective name for various copper acetates. Their color varies from blue to green.It reacts with binding media such as oils and resins and forms transparent oleates or resinates. This property has been utilized for preparing transparent green glazes called copper resinates by dissolving verdigris in warm turpentine resin mixed with mastic and wax.Neutral verdigris is neutral copper acetate with the formula Cu(CH3COO)2·H2O. It can be prepared by solving basic verdigris in acetic acid.Basic verdigris can contain several forms of copper acetates such as [Cu(CH3COO)2]2·Cu(OH)2·5 H2O or Cu(CH3COO)2·Cu(OH)2·5 H2O which are both blue. The following copper acetate shows green color: Cu(CH3COO)2·[Cu(OH)2]3·2 H2O.The pigment, in general, is not very stable and decomposes on heating, they are soluble in dilute acids and react with alkalis forming copper hydroxide. The painting materials change their color from blue-green to green with time for approximately one month. It had also a bad reputation for insufficient lightfastness but newer experiments do not confirm this fact. The pigment darkens when mixed with sulfur-containing pigments such as ultramarine or orpiment.Copper acetate also occurs naturally as the rare mineral hoganite.
Names
Copper rust, Spanish greenPG 20, CI 77408Vertegrez, from Old French verte grez (13c.), verte de Grece (late 12c.), literally “green of Greece,” from obsolete French verd, from Latin viridis From Online Etymology Dictionary
Preparation
Basic verdigris can be prepared by bringing copper in contact with acetic acid vapor, water vapor, and air. The neutral pigment is formed by dissolving basic verdigris in acetic acid.Illustrated instructions for the preparation of this pigment together with historical recipes can be found in Travelling Scriptorium by the Yale University Library.
History of Use
Verdigris has been in use since prehistoric times until the present day. It was employed for green tones in landscape or interior paintings as it was the most intense green pigment at the time of the renaissance. With the arrival of modern green pigments such as emerald green and viridian the use of verdigris ceased. The following graph gives the frequency of its use in the paintings of the Schack Collection in the Bavarian State Art Collections in Munich (1).An extensive collection of occurrences of verdigris in paintings from several historical periods can be found in the blog post ‘Pigment: Copper rust, Verdigris and Copper Resinate by The Eclectic Light Company.Examples of use
Quote
The numerous chimneys with their fantastic shapes rose grimly in the moonlight, like a strange band of goblin sentinels, perched of the roof to watch the mansion. The general effect was that of an ancient structure falling to decay, deserted by all inhabitants save the rats that gnawed the wainscot along the thick old walls. The door-plate that glittered on the faded door, half covered as it was with rust and verdigris, with its saintly name afforded the only signs of the actual occupation of Monk-hall by human beings: in all other respects it looked so desolate, so time-worn, so like a mausoleum for old furniture, and crumbling tapestry, for high-backed mahogany chairs, gigantic bedsteads, and strange looking mirrors, veiled in the thick folds of the spider's web. The Quaker City; or, the Monks of Monk Hall, part 1, chapter 7 "The Monks of Monk-Hall" (1844)
Source: George Lippard
I disagree with those who assert that Titian and El Greco painted on a tempera underpainting. ...In contrast to Titian, El Greco very frequently employed glazings ...In El Greco we find a curious combination of tempera school ideas associated with a freedom of the brush stroke surpassing that of his master, Titian. Like the tempera painters, El Greco often underpainted in grisaille and glazed upon such a monotone underpainting the fiery hues of madder lake, verdigris, azurite blue and yellow (probably Indian yellow). This... largely accounts for the brilliance and extraordinary luminosity... But El Greco's grisaille... was brushed on roughly and the texture of the superimposed color often does not correspond with that of the grisaille. This... is an entirely unorthodox method. Entirely unconventional also was his use of the madder, which, at times, he applied with an extreme impasto defying the nature of this glazing color. Frederic Taubes, Studio Secrets (1943) pp. 10-11.
Source: El Greco
The two oxides [cuprous oxide & cupric oxide of copper were used in glass-making; verdigris was manufactured and put to several uses; white lead was used as a cosmetic by the Athenian ladies, and found further use as a medicine; red lead was used as a paint; stibium, or native antimony sulphide, was used as a paint for the eyelashes, and is still used for that purpose in the East under the name of kohl; black oxide of manganese was used in glass-making, especially for clearing up darkened masses, and so got its name of pyrolusite; the native carbonate of zinc was also known and used; the sulphides of arsenic, orpiment and realgar, were well-known pigments.
Source: A Short History of Chemistry
