Consolidating stucco

Amir Hosein Karimy <ahkarimy [at] yahoo__com> writes

>I am am working on a stucco mihrab (gypsum) in a hot arid city. The
>ornaments have became very powdery with poor stability of layers.
>which consolidant do you propose to use on this case? and also which
>coating material?  Does anyone have any recommendation about the
>percentage or solvents?

The Tg (glass transition temperature) of any consolidant is a
significant factor. It would be helpful to know what conditions the
mihrab will be kept in - what is the maximum temperature reached in
the room where it is kept, is it in use/on open display or kept in a
case which would protect it from dust?  Although you might normally
prefer a more stable copolymer such as Paraloid B72 (which can work
extremely well for such materials), if the temperature is likely to
reach 35 deg. C it would be more sensible to consider a resin with a
higher Tg such as Paraloid B4 (Tg 50 deg. C) or B44 (Tg 60 deg. C)

The conditions when the consolidation takes place could also have a
considerable effect on the results. Ideally conditions should be
much cooler than the summer maximum, and kept as stable as possible
to control the rate of evaporation of the solvent, allowing
sufficient penetration and preventing darkening of the surface.
Testing different methods and materials would be very helpful, if
there is time for this. There's an interesting article from 2011
comparing the effects of temperature on various polymers at

    <URL:http://bit.ly/Mw02HP>

for example.

Helena Jaeschke
Conservation Development Officer
Renaissance Southwest


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                  Conservation DistList Instance 26:11
                 Distributed: Saturday, August 4, 2012
                       Message Id: cdl-26-11-004
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