Laser Cleaning External Alabaster: High Speed Timelapse
September 13, 2018 | By Hirst-Conservation |
Work on this unique alabaster archivolt of the Norman doorway dating from ca. 1160 is underway at St Mary’s Church, Tutbury, with a programme of pre-consolidation and meticulous laser cleaning. We couldn’t resist documenting the dramatic transformation with some very high speed time lapse recordings.
The doorway is of outstanding significance as it represents ‘the earliest example of English alabaster carving (ca.1160) and the only instance of its use in an exterior arch in the country’ but concerns about the condition of the alabaster elements were raised when a large section became detached, causing significant material loss. This instigated a series of condition surveys and treatment trails and a conservation strategy has been developed with architects Robert Kilgour. During the assessment it became apparent that the crust formation on the surface of the alabaster contributes significantly to the deterioration of the material and prevents the conservation/consolidation of the stone material. Therefore, cleaning of the alabaster elements forms an integral part of the conservation treatments. Due to the fragile condition of the stone laser cleaning provides the most suitable method as it does not require direct surface application or any aftercare to remove residuals.
To reduce the risk of any material losses during the laser cleaning, the most friable areas have been pre consolidated by a combination of injection of nano-lime and lime-based filleting repairs. Laser cleaning is nearing its completion so that the next phase of further consolidation including mortar repairs, grouting and the application of sacrificial shelter coating can be implemented. Look out for our progress updates!
For more information about this wonderful church visit the project website http://tutburystmarys.org/priory-projects/copaa
Being conservators rather than filmmakers we have tried a few different methods of recording, and indeed attaching cameras to scaffold. Stone 24 was a taken as a video using standard Panasonic camera, and edited using adobe premiere pro. Stone 27 was all on the phone using framelapse app and edited on adobe clip: a much more convenient workflow when on the scaffold, but the quality is better suited to small screens.