The conservator then tested the solubility of both the surface coating
and the underlying decoration on the drum using a series of solvents.
The coating was readily soluble in deionized warm water (indicating
that it was shellac, not varnish), but the colorant over other areas
required stronger solvents: acetone and methylene chloride. Clearly,
the surface was not the expected clay slip. Further tests on the
surface flakes, removed with a needle tool and a small scalpel,
indicated that it was some kind of paint.
After test results were in, the painstaking task of dismantling the old
restoration was begun. Using the same solvents and a large quantity of
cotton swabs, the conservator successfully removed the shellac,
over-paint, fill materials, and adhesive with virtually no loss of
original surface. The Nasca artist's polychrome slip decoration was
revealed to be in remarkably good and stable condition.
The Nasca drum fragments were reassembled with Acryloid B-72, a
synthetic thermal plastic resin that does not embrittle or discolor
over time. Even more important to modern conservators, this adhesive is
readily
removable ("reversible") with solvents. Areas of large loss were
reconstructed using hydrostone (gypsum) and an emulsion adhesive. The
original, slipped decoration of Nasca birds will remain visible to
scholars and to the museum-going public.
