Stains on marble

Andrew Thorn <artcare [at] iprimus__com__au> writes

>Eric Miller <eric.g.miller [at] btinternet__com> writes
>
>>We are currently cleaning a marble fireplace that has yellow/brown
>>tar stains that do not respond to our attempts at removal. Laser
>>cleaning works but it turns the marble yellow. (A 1999 DistList
>>entry affirms Synperonic N, but this is no longer available.) Any
>>suggestions?
>...
>Thank you for your comments on the impact of laser cleaning on
>marble. Gradually some critical assessment of this wonder tool is
>emerging at last.

To the person who has only a hammer, every problem looks like a
nail. The laser is only another tool for conservators, requiring the
same discrimination, user skills and understanding as any other. Its
capabilities, advantages and disadvantages are as unique, though
perhaps less understood, as those of solvents, poultices, a cotton
swab or a scalpel. Any of these can be misused out of inexperience,
carelessness, or a lack of understanding of its limitations and
dangers, and indeed no one could argue the terrible damage that has
been wrought by well intentioned restorers and conservators wielding
these arguably 'simple' tools. Lasers, new to the scene, require
even more due diligence and caution on the part of conservators than
such long-standing conservation tools, materials, techniques and
technologies that have benefited from generations of development-
trial, error, research, and publication.

I certainly agree that conservators must be skeptical, especially of
advances that may be driven in part by economic and commercial
forces. There are no "wonder tools". Practitioners without
selectivity, sensitivity, education and experience who seize on such
concepts should immediately find other work more suited to their
philosophical approach--perhaps creating mortgage derivatives or
engineering credit-default swaps.

I hope Andrew Thorn would agree that to dismiss the class of
physical and chemical interactions and reactions that laser
wavelengths can produce as tools for conservation would be as
limiting as to dismiss the activity of poultices, gels, detergents,
and even (safer) solvents.

Tony Sigel
Conservator of Objects and Sculpture
Straus Center for Conservation and Technical Studies
Harvard Art Museum
32 Quincy Street
Cambridge, MA 02138
617-496-1903
Fax: 495-0322


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                  Conservation DistList Instance 22:52
                 Distributed: Thursday, March 12, 2009
                       Message Id: cdl-22-52-001
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