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Subject: Shellac stains in terracotta

Shellac stains in terracotta

From: Linda Roundhill <artsconservation>
Date: Thursday, December 6, 2007
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

                  Conservation DistList Instance 21:35
                Distributed: Tuesday, December 18, 2007
                       Message Id: cdl-21-35-005
Received on Thursday, 6 December, 2007

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