Primal B60A

Stefka Bargazova <sbargazova<-at->britishmuseum<.>org> writes

>My colleague Duygu Camurcuoglu and I have recently started testing
>Primal (Rhoplex) B60A for consolidation of cracks and flaking
>surfaces of archaeological ceramics as alternative to Paraloid B72.

I have not specifically worked with Primal B60 A, but I have done
extensive research on using PVA emulsions, acrylic emulsions and
acrylic colloidal dispersions for the consolidation of ceramics and
mud brick.

I found that the acrylic colloidal dispersions were the most useful,
owing to their better stability, better penetration and neutral pH,
and the dispersion of choice was Primal (Acrysol) WS-24, whose
properties are similar to that of Paraloid B-72.

Emulsions are different than acrylic colloidal dispersions, and one
of the major disadvantages of the acrylic emulsions is the high pH,
and Primal B60 A is no exception.  Rohm and Haas lists it at a pH of
9.6.  It also has a minimum film formation temperature of 9 deg. C
and is very soft (< 1.0 Tukon hardness).  It also has a very high
viscosity (1500 cps), so will not penetrate very well, and has a
very low glass transition temperature (16 deg. C).

More important, acrylic emulsions remain extremely sensitive to
water after application, and will swell, or possibly dissolve, in
prolonged soaking in water, so it would not be appropriate at all
for consolidation and then salt extraction.  This was published in a
British Museum publication, that I do not have a reference for.

In general, the only reason to consider a water-based system for the
consolidation of archaeological ceramics would be if the ceramics
were very, very large, and the use of a solvent would be difficult.
B-72 penetrates extremely well when dissolved in acetone or an
acetone:ethanol mixture of 90:10.  It has also been documented as an
excellent consolidant for later salt extraction, as soluble salts
can be extracted through the consolidated ceramic.

References for acrylic colloidal dispersions used on archaeological
ceramics and mud brick are:

    Koob, Stephen P.
    "Consolidation with acrylic colloidal dispersions",
    in Preprints of the AIC ninth Annual Meeting, Philadelphia,
    1981, pp. 86-94

and

    Koob, Stephen P., Rogers, Mark H., and Sams, G.K.
    "Preserving the eighth century B.C. mud brick architecture at
    Gordion, Turkey: approaches to conservation"
    in the 6th International Conference on the Conservation of
    Earthen Architecture, Adobe 90 Preprints, 1990, pp. 289-294.

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


                                  ***
                  Conservation DistList Instance 29:40
                   Distributed: Sunday, March 6, 2016
                       Message Id: cdl-29-40-002
                                  ***