Paraloid B-72

Eleonore Kissel <eleonore.kissel [at] conservationpreventive__com>
writes

>... does anyone have an idea why titanium white (and not, for
>instance, zinc white) has been recommended in previous the National
>Parks Services Conserv-O-Gram, at least one Conservation DistList
>posting (Stephen Koob, 2002) as well as personal communications I
>have had with colleagues, when making a white opaque
>Paraload/Acryloid B-72 solution?

The NPS Conserve-O-Gram refers to a mixture developed for labeling
museum collections.

Many museum staff who number collections want to use a white ink.
25% B-72 in acetone with rutile titanium white pigment is the most
light stable white pigment we could find for these people (the zinc
oxides alter over time, and numbers may become illegible).  Many
museums prefer a white area written on with a black number rather
than writing a white number on a dark object surface. Unfortunately,
a large number of museums used the white directly on the surface of
artifacts as the first base coat, instead of on top of a clear base
coat barrier.  Light Impressions, the major supplier of this
material, based on the recommendations of NPS, did not supply the
material with adequate instructions for use.  Thus, people used it
in ways that might permanently damage collections and could harm
their health (most numbering occurs in areas with no ventilation or
air movement, such as storage areas).  In order for the rutile
titanium white to go into suspension in the acrylic, it a few drops
of toluene were added to the mix.  Toluene's health effects are more
severe than the acetone, as most of us working with these solvents
know.  However, this information was not transferred to the primary
consumer, the museum staff person trying to keep inventory control
of the collection.

Because of its misuse and a misunderstanding of its properties, we
have discouraged people from using the B-72 and titanium white mix.
Plus, if you have ever made it, it is a nasty, horrible process,
especially if you are making large batches.  Instead, we steer
people to Golden's liquid acrylics, titanium white and emphasize
that it must be applied over a clear base coat of B-72 or B-67
(depending on the artifact substrate being numbered).

The other warning we give is that some acrylics may contain trace
amounts of ammonia, which can damage metals, in particular copper
alloys.  We do not know if the Golden products have ammonia or not.

I hope this why titanium dioxide (only the rutile form) is
recommended as a white pigment by NPS and a little on the history of
its use and misuse in America's museums.

Helen Alten, Instructor for the on-line course
MS 208: Applying Numbers to Collection Objects
next offered July 5-July 31, 2006 at
<URL:http://www.museumclasses.org>
Northern States Conservation Center
PO Box 8081
St. Paul, MN 55108
651-659-9420


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                  Conservation DistList Instance 19:29
                 Distributed: Tuesday, December 6, 2005
                       Message Id: cdl-19-29-005
                                  ***