Damaged ebonized finish

I am preparing a sideboard with overhead cupboards designed by
E.W.Godwin (1867) for the first display at the redeveloped NGV
International building. The ebonized finish on the upper surface of
the sideboard exhibits areas of damage. The damage is characterised
by a matte appearance, some areas of raised grain, and other
localised spots remaining tacky that react to pressure like stiff
dough (when examined microscopically). The damage appears to have
been due to prolonged contact with water as the areas correspond
with the spaces between the cupboards. The undamaged finish, likely
to be shellac-based, is soluble in ethanol, pet spirits and slightly
in acetone. The damaged areas are soluble in acetone, ethanol, pet
spirits and slightly in Shellsol T.

Ideally we would like to treat these areas so that they have
comparable sheen to the surrounding undamaged finish, however due to
the delicate nature of the surface we currently cannot apply waxes
or other finishing materials as mechanical action can shift the
tacky areas. I would appreciate any advice on how to treat the
damaged ebonized surface preferably without removing the original
finish.

Suzanna Shaw
Conservator of Frames and Furniture
National Gallery of Victoria, Australia


                                  ***
                  Conservation DistList Instance 17:2
                  Distributed: Thursday, June 19, 2003
                        Message Id: cdl-17-2-016
                                  ***