Shellac stains in terracotta

Susan White <smwhitewhite [at] hotmail__com> writes

>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.

One of my very first projects as conservation intern years ago was
treating a white ground lekythos that had been previously mended
with shellac. The shellac had turned dark brown with age and had a
distressing habit of staining the white ground if not approached
cautiously.  As Susan White suggests, methanol worked better in
dissolving the shellac than ethanol. Sometimes one needs the more
toxic solvent to do the job.

Colleen Day
Parks Canada Atlantic Service Centre


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                  Conservation DistList Instance 21:35
                Distributed: Tuesday, December 18, 2007
                       Message Id: cdl-21-35-009
                                  ***