Preservation Of Murals On Salt Loaded Masonry
Vaults By Electromigration
Author(s)
I. Rörig-Dalgaard & L. M. Ottosen
Abstract
Salt induced deterioration of murals in churches has increased within the last
decades in Denmark. However, no lasting preservation method has been found.
Either murals are repainted by conservators or placed in climate chambers which
give the deterioration a break. Ion migration in a solution in an applied electric
DC field is termed electromigration and is a well known and accepted transport
process. In wet porous clay brick masonry, which most Danish church vaults
consist of electro migration is expected to be an efficient transport mechanism
for ion extraction out of the vaults. This idea was tested in the present work.
Electromigration experiments in bricks with low NaCl concentration (spiked
into the brick by soaking) showed that it is possible to clean a brick to its initial
ion content new from the factory. An experimental setup which is applicable
under real conditions and with ion contents corresponding to heavily polluted
church vaults (1.4 weight% chloride) showed significantly decreasing ion
contents as a function of time. Experiments are ongoing to reach a harmless ion
content which is thought to be a matter of duration and optimization of
experimental conditions.
Simultaneously with the electromigration process varying extends of acid and
base is produced due to electrode reactions. Clarifying experiments showed
extreme pH changes and pointed out the need for developments of electrode
setups to avoid these changes. New experiments with the developed electrode
units reduced the pH changes remarkably, which make the method usable in
connection with cultural heritage.
On the basis of successful laboratory results electrokinetics for extraction of
ions from masonry vaults might be the missing lasting method to extract the
damaging salts and thereby preserve the murals.
Keywords: electromigration, chloride extraction, pH stability, church vault.
Keywords
electromigration, chloride extraction, pH stability, church vault.
Related Book
Other papers in this volume
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