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Subject: Paraloid B-72

Paraloid B-72

From: Stephen Koob <koobsp<-a>
Date: Wednesday, November 23, 2005
Eleonore Kissel <eleonore.kissel [at] conservationpreventive__com>

>... 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?

I believe there are published reports of B-72 not behaving well in
outdoor exposure situations (e.g.,loss of adhesion, yellowing from
pollution/bird excrement) but this is not surprising, as it was
never designed, nor intended, for outdoor use.

However, I can attest to the fact that it does hold up incredibly
well, indoors, even under adverse conditions, such as archaeological
storerooms, with no climate control, experiencing ranges of humidity
from 10-100%, and temperatures of -10 deg. C to 35 deg. C, and this
is true, even for archaeological glass, one of the most difficult to
repair materials in the archaeological record. If the temperature
exceeds 40 deg. C for any extended length of time, the stability of
the resin may be compromised, owing to its glass transition
temperature (Tg), of 40 deg. C.

As to the use of titanium dioxide to opacify the resin, I can only
say that titanium dioxide produces a significantly more opaque
coating than zinc white, and therefore, much less pigment is
required to obtain an opaque white (and isn't titanium dioxide
significantly more stable than zinc white?).

Stephen Koob
The Corning Museum of Glass
One Museum Way
Corning, NY 14830

                  Conservation DistList Instance 19:29
                 Distributed: Tuesday, December 6, 2005
                       Message Id: cdl-19-29-006
Received on Wednesday, 23 November, 2005

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