MCI Project Summaries 2008 - Smithsonian Institution

MCI 6270 Sculpture: Head of John F. Kennedy by Robert Berks
MCI Staff: Carol A. Grissom, Nicole C. Little, Judy Watson
Berks’ s Bust of John F. Kennedy was requested for loan by the Secretary of the
Department of Interior for his office, and the head of conservation at the National Portrait
Gallery was concerned that the highly colored patina on Berks’s bust would react adversely in
the uncontrolled environment at the Department of Interior. The cast-bronze head generally has
a dark brown patina, but its many interstices, which are part of its style, have duller surfaces
coated in an irregular pattern of powdery green, red, and rusty orange-colored material. Low
magnification did not indicate any active formation of crystals in the green patina, which might
suggest the presence of copper chlorides such as the deleterious paratacamite, but copper
chlorides are commonly present in solutions used to produce green-colored patinas. X-ray
diffraction analysis of a sample was inconclusive, but SEM-EDS analysis clearly showed the
presence of chlorides. Thus, it was advised that the head not be lent, since copper chlorides can
be activated in the presence of moisture.
154