Adhesive and filler for alabaster

Robert K. MacDowell <macdowell_r [at] mediasoft__net> writes

>We have just received for possible conservation a few lamp parts
>made of alabaster and would very much appreciate hearing from anyone
>who has had experience in bonding and filling missing chips and
>other pieces with regards to the adhesives they would choose and the
>filler material.
>...
>
>I'm concerned about the hardness of all of the repair materials we
>have in relation to the very soft nature of alabaster and the
>problems that will likely arise in trying to shape any fills without
>damaging the surrounding, soft, alabaster.

Wherever possible I use Paraloid B-72 for bonding alabaster.  But
when it comes to fills, despite their attractive qualities with
respect to compatibility with the substrate and ease of
reversibility, I find bulked acrylic resins like Paraloid, even with
the addition of xylene, somewhat unattractive for use in this
application.  And very often I find that there is simply no
substitute, from an aesthetic and workability standpoint, for bulked
and color-matched epoxies, particularly where translucency is of
paramount importance.  I get around their inherent vices by thorough
consolidation of the entire area of loss prior to filling and--most
importantly--by shaping and polishing the fill material using
acetone, either on a spatula or on a swab, before it has fully
cured.  I don't shape or polish with abrasives after the fill
material has cured, thus avoiding the potential damage you describe.
Some of the longer-cure epoxies (Epotek series and Fynebond) are
excellent for this purpose as they are still able to be taken down
and shaped with acetone or a scalpel even after 18 hours.

Alternatively, where this process is not possible or advisable,
there is an excellent method explained very clearly and fully in

  Gansicke and Hirx,
  "A Translucent Wax-Resin Fill Material for the Compensation of
  Losses in Objects."
  JAIC vol 36, no. 1 (Spring 1997): pp17-29,
  <URL:http://aic.stanford.edu/jaic/articles/jaic36-01-002_indx.html>

Rachel C. Sabino-Gunaratna
Assistant Conservator of Objects and Sculpture
The Museum of Fine Arts, Houston
5601 Main Street
Houston, TX 77005
USA
713-639 7852
Fax: 713-639 7780


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                  Conservation DistList Instance 21:3
                  Distributed: Thursday, May 10, 2007
                        Message Id: cdl-21-3-006
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