MCI Project Summaries 2008 - Smithsonian Institution

MCI 6207 Cleaning of Marble with Ammonium Citrate
MCI Staff: Claire Gervais, Carol A. Grissom, Nicole C. Little, Ron H. Cunningham, Mel J.
Wachowiak
This study focused on cleaning marble with ammonium citrate, a product often
used with success by conservators, but for which almost no critical evaluation can be
found in the literature. A systematically investigate was conducted to better understand
its action on the surface and establish –if possible- the optimal conditions of utilization of
this cleaning agent. In particular, the solubility of calcite (the main component of marble)
as well as its kinetics of dissolution in solutions of ammonium citrate at different pH and
different concentrations were established. The impact on marble surface was monitored
by characterizing the surface of polished marble tiles before and after application, by
means of several techniques (e.g., gloss measurements, micro-drop experiments,
scanning electron microscopy, and 3-D scanning), In a final step, the optimized solution
(formulation and mode of application determined by previous analyses) was applied on
weathered/dirty marble statues or fragments. A paper on this project has been submitted for
publication.
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