B72 is a copolymer resin that is primarily used in art,
architectural and artifacts conservation as an adhesive and a consolidant of
powdery surfaces. It probably has some water repellent properties as
well. I don’t see a problem per se with exterior use. Its
glass transition is relatively high, but you can also increase it by mixing it
with other types of resins. B72 is used in solution, and the
concentration of the solution will affect how far it penetrates into a
substrate. B72 is probably more permeable than the paint, so vapor
permeability is not likely an issue. You can find out more about B72 and
other materials through the website of the American Institute for the Conservation
of Historic and Artistic Works (AIC): www.conservation-us.org.
From that website you can search the Journal of the American Institute for Conservation
for articles on B72, mural conservation, etc.
The key to this issue is understanding the paint layers—what
they are comprised of (likely an oil or alkyd binder with lead pigments), how
many layers there are, and what the nature of the deterioration is. Your
best bet is to consult with a mural or paintings conservator, who will have a
grasp on what different treatments will do with respect to the paint and the
substrate (penetration, adhesion, differential expansion/contraction, re-treatability,
etc.).
Mary E. Slater
Associate | Architectural Conservator
ARCHITECTURAL RESOURCES GROUP, INC
Architects Planners
Conservators
Pier 9, The Embarcadero, Suite 107 | San Francisco, CA 94111
415.421.1680 x246 | 415.421.0127 fax | [log in to unmask]
San Francisco | Pasadena | Portland
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From: The listserv where
the buildings do the talking [mailto:[log in to unmask]] On
Behalf Of Rudy Christian
Sent: Thursday, September 02, 2010 5:29 AM
To: [log in to unmask]
Subject: [BP] Paint preservation question
Well folks, here's another inquiry that came to PTN that
seemed best mangled by all the Pinheads, not just this one. My suggestion would
be to build a timber frame enclosure over it and keep the rain and sun off!
>My name is Sondra Carson and I am a member of the Landmark
Preservation Commission (LPC) in Fort Collins, Colorado. Currently, we are
discussing various options to protect a Coke-a-Cola sign that was painted on a
brick wall. One of the options presented to the LPC included using
Acryloid B 72 to prevent any further deterioration of the flaking paint. I have
thoroughly read Preservation Briefs 1 & 2 published by the National Parks
Service (published circa 2000). Based on these publications, it is my understanding
that water repellents are only indicated as a means to control deterioration or
dissolution when water penetration is problematic after repairs have been made
to make it watertight.
Even though these water repellents are relatively vapor permeable,
I couldn't find any literature/journal articles that suggest the primary
indicated use of Acryloid B72 as a means to preserve a historic painted
advertisement. In essence, I've been looking for the effects of water
repellents layered over lead based paint on vapor permeability on a masonry
wall. I'm guessing it would decrease but I don't know how drastic.
So, my question... Is Acryloid B72 (or any other water
repellent) ever indicated as a protective coating over a historic lead based
paint advertisement on an exterior masonry wall? I’ve been told Acryloid
B72 is considered a new and safe water repellent being used in the conservation
of painted advertisements but I am unable to find any research
studies/literature/journal articles that can back up this opinion.
I would deeply appreciate it if you could shed some light on this
for me.<
Suggestions?
Rude E
Helping put the *Shine* on HP
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