Earthenware ceramic

Helen Privett inquired about how to treat ferric oxide stains on a
cream colored earthenware horse figure.  It is assumed that the
dowels were secured into the ceramic with an adhesive.  I would
suggest first breaking the bond of the adhesive with the appropriate
solvent, then attempting to pull the dowels out.  If that does not
work, then if possible, you might try carefully drilling around each
dowel with a fine bit just enough to weaken the bond enough to pull
it out.

Try reducing the intensity of the staining with 3% hydrogen peroxide
solution on swabs.  If that is not effective, then try a 10% oxalic
acid solution in deionized or distilled water.  Rinse the acid off
and don't soak the object in it as it will tend to recrystallize if
not completely removed. The acid will complex the ferrous ions,
turning the solution a greenish yellow.  Test a small area first to
see the effect of the solution on the surface and if the staining
gets drawn in any deeper.

Paul S. Storch
Senior Objects Conservator/Section Head/Internal Unit Preparation
    Specialist
Daniels Objects Conservation Laboratory (DOCL)
B-109.1, Minnesota History Center
345 Kellogg Blvd. West
St. Paul, MN  55102-1906
651-297-5774
Fax: 651-297-2967



                                  ***
                  Conservation DistList Instance 16:29
                 Distributed: Friday, October 25, 2002
                       Message Id: cdl-16-29-002
                                  ***