Consolidating polychrome limestone altarpieces

The treatment of eight polychrome limestone altarpieces will include
desalination, stone cleaning and paint consolidation. We will have
to carry out the consolidation of the fragments after desalination.
Ethyl silicates after hydrolysis and condensation originate
colloidal silica that is deposited inside the porous structure of
the stone.

The silica molecules are chemically similar the silicate minerals
and therefore they exhibit a very good compatibility with stones
having a silicate-based composition. In theory the ethyl silicate
would not show any affinity to carbonate minerals but previous
experiences in the museum with limestone sculptures revealed the
contrary. In fact an increase in cohesion and strength of the stone
was reached. Studies carried out at LNEC (National Laboratory for
Civil Engineering) reveal that the main positive characteristics of
these types of consolidants are the very high capacity for migration
inside the carbonate stones, the slight reduction in water vapour
permeability and the absence of strong interfaces between treated
and non-treated zones.

Do you think that applying an ethyl silicate to limestone
altarpieces is the correct choice?

    **** Moderator's comments: For more information about this
    project, see Conservation DistList Instance: 19:15 Thursday,
    September 15, 2005


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                  Conservation DistList Instance 19:16
               Distributed: Thursday, September 22, 2005
                       Message Id: cdl-19-16-020
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