Page 184 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

Notes
ι Plutarch Moralia, the Oracles at Delphi no longer 12 Lead in cast bronzes is present as a series of dis­
given in verse (Plutarch 1984). crete globules since lead is not soluble in copper
2 Vagbhata Book of Rasaratnasamuchchaya (Ray or tin as the bronze cools; the lead is distributed
1956:170). as small globules in interdendritic regions of the
3 Pedanius Dioscorides De materia medica 5.98 bronze casting. In cases where gravity segregation
(Dioscorides [1933] 1968). has occurred, there may be some settlement of the
4 Pliny the Elder Natural History 34.2 (Pliny 1979). lead toward the lower areas of the casting.
5 Pliny 34.24. 13 Shigeo Aoki, letter to the author, 15 February 1998.
6 Johann Agrícola De natura fossilum (Agrícola 14 The thermal spraying technology was origi­
[1546] 1955). nally developed in Switzerland around 1900. It
7 The bronze statue was cast in Paris at the Alexis utilizes a metallizing process in which a compres­
Rudier foundry and unveiled in 1927 in front of sor thrusts metallic powder into an oxyacetylene
the Parliament buildings in Ottawa. flame, and the semimolten metallic particles are
8 Helena Strandberg, letter to the author, 10 Sep­ then sprayed onto the substrate to be coated. This
tember 1998. process is still used in industry today, although
9 See note 8. more sophisticated facilities usually employ a
10 French artist Frédéric-Auguste Bartholdi (1834 - plasma-spraying apparatus; thermal spraying is
1904) and the famous engineer Alexandre Gustave still utilized by smaller operators.
Eiffel (1832 -1923) were instrumental in designing
and building the monument. For several years,
the statue was under the protection of the Light-
House Board, and in 1890 authorities proposed
protecting the statue by treating it like a light­
house and painting the entire monument white.
11 While the exterior of the statue was left
alone, the interior was painted with a variety
of materials in an attempt to waterproof the
structure. The galvanic reaction that might have
occurred between the copper and the wrought
iron armature was originally prevented by using
asbestos cloth soaked in shellac. When the monu­
ment underwent restoration (1988-94) , a stainless
steel armature —steel type 316L U N S S3i6o)—was
(
employed to replace the wrought iron, and a layer
of Teflon was placed between the copper and the
steel. The force of the corrosion of the original
wrought iron had pulled several rivets through
the copper sheets; pressure also caused the copper
skin to bulge outward. This cannot be repaired
now without damaging the external patina.

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