Krista asks for help with cleaning Mesoamerican pottery.
     I know nothing of the firing processes of your pieces, and nothing
of the chemical composition of your paint, and so advise you to test
the method I am about to describe.
     For cleaning ancient Greek ceramics, both "painted" and coarse
ware, we use hydrochloric acid as described by R M Cook _Greek
Painted Pottery_ (Methuen 1960) 285f:
     "If water is not enough - and it rarely is - a more efficient solvent is
dilute hydrochloric acid.  Though neat hydrochloric acid does not
damage well made and well preserved Greek pottery, one part of acid
to twenty parts of water is normally ample.  The specimen should be
saturated with water before it is put into the solution of acid.  If it
fizzes or bubbles there is no cause for alarm.  After twenty-four hours
or so it may be taken out and brushed lightly.  If a deposit still
remains, it can be steeped longer or in a stronger solution of the acid.
 When finally removed the specimen should again be soaked and
rinsed in water, and then put aside to dry.
     "Pottery that has been cleaned sometimes develops whitish
crystals on its surface, caused by salts that have penetrated the clay.
The cure is soaking in plain water."
     I have used this for terracottas with vestiges of post-firing matt
paint, and have found that the acid does not affect the paint.
- Anne Mackay
 
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(Prof) E A Mackay
Department of Classics
University of Natal
Durban 4001
South Africa
E-Mail: [log in to unmask]