Page 348 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

Weil (i996) notes that the famous statue of David by Donatello (i386-i466), 1 4 which
was cast during the i430s, was covered with a dark lacquer. This helped to conceal small cast-
ing flaws and repairs, which are reputedly a common feature of fifteenth-century Florentine
bronzes. Donatello's sculpture, shown in PLATE 68, is now in the Museo Nazionale del Bargello
in Florence and once stood in the courtyard of the Medici Palace.
A similar use of dark lacquer to conceal flaws was discovered when the lacquer and corro-
sion products were cleaned from the bronze doors cast in 1433 - 45 by Antonio Averlino (Filarete)
(1400-1469) for St. Peter's Basilica in Rome. The doors contained numerous repairs and were
made in different alloy components; patination was used to disguise the uneven surface appear-
ance. In contrast, the bronze doors on the Church of San Michèle at Monte Sant'Angelo, Italy,
were probably finely cast, since they have an inscription from the sponsor, Pantaleone d'Amalfi,
to the effect that the doors need to be cleaned once a year to retain their bright and shiny appear-
ance (Federici 1969).
Gauricus (Gaurico 1969) mentions that polished bronze or brass will turn yellow by placing
it on an incandescent plate and that the surface of a bronze can be blackened by holding it over
the smoke of damp or wet-burning hay. Sometimes drying oils, colored lacquers, or varnishes
were applied directly to the polished metal surface to give it a warm glow or to darken it. Vasari
describes the use of oil or varnish to turn the surface black, and Gauricus suggests coating it with
pitch. In archival material concerning a bronze mythological group by Massimiliano Soldani
(1656-1740), Avery (i996) discovered an interesting reference to patination after repairs had
been made. An English dealer identified as Zamboni had written to Soldani asking for his advice
on how to repair the bronzes damaged during shipment. The sculptures had been mended by
soldering but this had ruined the patination. In his reply, dated 28 April 1725, Soldani advised
never to solder the parts but rather to fix them together with molten bronze of the same alloy as
that of the cast so it will have the same color. To restore the damaged patina, Soldani continued,
it is necessary to remove the old one first by bathing the bronze in lye and using a bristle brush
to remove the varnish. Then the surface is to be cleaned with pungent lemon juice that is
rubbed on the metal with smooth white sand and a wooden stick. Finally, the sand and juice are
removed with water, and the metal is dried with a cloth and by warming. Soldani's new patina
was made by first applying clear walnut or linseed oil with a bristle brush, then following this
with a coating of finely ground hematite or lapis rouge. Soldani cautioned against applying too
much hematite on the rough areas to prevent the material from lodging in recesses and caus-
ing them to appear dark and subfusc. This patina is essentially oil with a glazing of hematite that
is left to dry.
A fine translucent tawny patina on a Renaissance bronze is shown in PLATE 69. This
Laocoön, by Giovanni Battista Foggini (i652 -1725) and dating from about 1720, is in the collections
of the J. Paul Getty Museum. Mercury, a bronze cast around 1559-60 by Alessandro Vittoria

S O M E A S P E C T S O F B R O N Z E PATINAS
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