St. John's Co-Cathedral is located within the fortified city of Valletta, the capital city of Malta.  Image © Katey Corda, 2012
Facade of St John’s Co-Cathedral in Valletta, Malta.
Interior of the Grand Masters’ Crypt of St John’s Co-Cathedral before conservation treatment.  Image © Courtauld CWPD
A large loss of painted plaster from the Crypt vault exposed the construction technique of keyed ashlar masonry, cut from the local globigerina   limestone. Image © Courtauld CWPD
large areas of the wall paintings were detaching and at imminent risk of collapse. Image © Courtauld CWPD
large areas of the wall paintings were detaching and at imminent risk of collapse. Image © Courtauld CWPD
Salt efflorescence, biofilms and dirt were hindering appreciation of the paintings and diminishing recognition of the Crypt’s significance. Image © Courtauld CWPD
Salt-related deterioration was causing powdering and loss from both the wall paintings and limestone tomb monuments. Image © Courtauld CWPD
Salt-related deterioration was causing powdering and loss from both the wall paintings and limestone tomb monuments. Image © Courtauld CWPD
Salt-related deterioration was causing powdering and loss from both the wall paintings and limestone tomb monuments. Image © Courtauld CWPD
Beginning conservation treatment in the Crypt. Image © Courtauld CWPD
Consolidation of powdering wall paintings. Image © Courtauld CWPD
Testing the strength of a custom grout for stabilization of the detached plaster. Image © Courtauld CWPD
Syringes, catheters, needles and pipettes were used to inject a custom grout into voids behind detached areas of decorated plaster.  Image © Courtauld CWPD
Syringes, catheters, needles and pipettes were used to inject a custom grout into voids behind detached areas of decorated plaster.  Image © Courtauld CWPD
Losses in the wall paintings were filled with a lime and sand mortar, compatible with the original materials.  Image © Courtauld CWPD
Salt efflorescence, loose dirt, and microbiological growth were cleaned from the wall paintings by dry dusting with paint brushes and carefully wiping with damp sponges.  Image © Courtauld CWPD
Salt efflorescence, loose dirt, and microbiological growth were cleaned from the wall paintings by dry dusting with paint brushes and carefully wiping with damp sponges.  Image © Courtauld CWPD
The wall paintings partially cleaned in the western apsidal area.  Image © Courtauld CWPD
The wall paintings during cleaning. A layer of salt efflorescence, loose dirt, and microbiological growth has been cleaned from the left side of the image but remains on the right.  Image © Courtauld CWPD
Detail of the wall paintings before (left) and after (right) cleaning. Image © Courtauld CWPD
Detail of the wall paintings before (left) and after (right) cleaning. Image © Courtauld CWPD
A consolidant was applied to the powdering limestone tomb monuments by syringe and needle.  Image © Courtauld CWPD
A consolidant was applied to the powdering limestone tomb monuments by syringe and needle.  Image © Courtauld CWPD
A consolidant was applied to the powdering limestone tomb monuments by syringe and needle.  Image © Courtauld CWPD
A consolidant was applied to the powdering limestone tomb monuments by syringe and needle.  Image © Courtauld CWPD
Detail of the limestone tomb monuments before (left) and after (right) consolidation and cleaning.  Image © Courtauld CWPD  
Detail of the limestone tomb monuments before (left) and after (right) consolidation and cleaning.  Image © Courtauld CWPD
During consolidation of the powdering limestone monuments.  Image © Courtauld CWPD
Detail of the limestone tomb monuments before (left) and after (right) consolidation and cleaning.  Image © Courtauld CWPD
A thick layer of dirt and microbiological growth was cleaned from the stone floor of the Crypt. Image © Courtauld CWPD
Detail of the Crypt stone floor before (left) and during (right) removal of a thick layer of dirt and microbiological growth. Image © Courtauld CWPD
A thick layer of dirt was cleaned from the inscribed marble plaques set into the floor of the Crypt. Image © Courtauld CWPD
Image of the inscribed marble plaques set into the floor of the Crypt before (left) and during (right) removal of a thick layer of dirt. Image © Courtauld CWPD
A section of wall painting obscured by layers of limewash was uncovered. Image © Courtauld CWPD
Uncovering a section of wall painting obscured by layers of limewash. Image © Courtauld CWPD
Detail of the Crypt before (left) and after (right) conservation treatment.  Image © Courtauld CWPD
Detail of the Crypt before (left) and after (right) conservation treatment.  Image © Courtauld CWPD
Detail of the Crypt before (left) and after (right) conservation treatment.  Image © Courtauld CWPD
The Crypt after conservation treatment.  Image © Courtauld CWPD
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