Shellac stains in terracotta

I am currently treating a group of unglazed Greek terracotta vessels
for a small museum.  Several of the pieces have been poorly restored
using shellac as an adhesive.  Unfortunately the shellac has badly
stained some of the pieces along the join lines.  I've used ethanol
poultices and have had little luck in removing them.  Does anyone
have any good ideas for safely removing old shellac stains from
terracotta?  I've heard methanol can sometimes work, but wanted to
check with others first before trying it.

Susan White
White Conservation Services


                                  ***
                  Conservation DistList Instance 21:33
                Distributed: Wednesday, December 5, 2007
                       Message Id: cdl-21-33-021
                                  ***