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.

You should try combinations of solvents, as that often has a
dramatically different effects than pure solvent alone.  I had a
badly conserved unglazed terracotta to work on and the stains from
the residual shellac were terrible.  They were greatly reduced by
poultices of 50:50 ethanol/acetone. You might experiment with
cocktail of methanol/ethanol/acetone also, but you may find residues
persist despite your best efforts.

Linda S. Roundhill
Art and Antiquities Conservation, LLC
18121 157th Ave NE
Woodinville, WA 98072
425-481-0720


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                  Conservation DistList Instance 21:35
                Distributed: Tuesday, December 18, 2007
                       Message Id: cdl-21-35-005
                                  ***