Building upon what David said, "reversibility" is a term that is full of
contradictions and levels of meaning.  For something to be truly reversible,
all of it must be removed from an object with no residue left behind.  In
practice, this never occurs.  Even on a smooth surface, molecules of the
coating material, like B-72, are left behind.  Reversibility of coatings
generally is used to mean that the coating can be dissolved in relatively
mild solvents that will not harm many (but not all) surfaces, and that it
remains similarly soluble as it ages.  Thus, B-72 is "marketed" as meeting
this definition of reversibility.  However, there are some surfaces and some
types of materials that can not sustain even the mildest solvents without
damage.  One example is surfaces that are crumbly.  And as David pointed
out, marking materials can be very difficult to remove from absorbent
surfaces.  The user must apply discretion to determine which surfaces and
objects are safe for specific marking materials.

The only truly reversible method of marking that I know of is a label placed
next to an object and not attached to it.  The next closest is an acid-free
string tag tied loosely to the object.  All other marking methods are not
truly reversible.  This includes pens, paints, and barrier coatings used
before these are applied.  The level of intrusion/absorption, and the
acceptability of this must be determined by the user for each object.
Generally, the museum profession has accepted a little bit of invasiveness
in a small area as a trade-off for marking objects.  But for certain
specific objects, alternative marking techniques will be required.

Marc

American Conservation Consortium, Ltd.
     4 Rockville Road
     Broad Brook, CT 06016
     www.conservator.com <http://www.conservator.com/>
     860-386-6058

*Collections Preservation Consultation
*Conservation Assessments & Surveys
*Environmental Monitoring & Low-Tech Control
*Moisture Management Solutions
*Collections in Historic Structures
*Collections Care Grant Preparation
*Conservation Treatment of:
     Furniture
     Painted Wood
     Horse-Drawn Vehicles
     Architectural Interiors

Marc A. Williams, President
     MS in Art Conservation, Winterthur Museum Program
     Former Chief Wooden Object Conservator, Smithsonian Institution
     Fellow, American Institute for Conservation (AIC)

> -----Original Message-----
> From: Museum discussion list [mailto:[log in to unmask]]On
> Behalf Of Kristy Caratzola
> Sent: Thursday, February 28, 2008 2:19 PM
> To: [log in to unmask]
> Subject: [MUSEUM-L] Reversiblity of B-72
>
>
> I've recently heard that B-72 Acryloid is irreversible.  If this
> is true why is it
> marketed as a liquid labeling product for Collections Objects?
> What should be
> used to label Collections Object that is reversible and archivally sound?
>
> Kristy Caratzola
> Planting Fields Foundation
> Oyster Bay, NY
>
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