Project overview

Project overview
The wall mosaic on the east wall of the St Erasmus Chapel, designed by JR Clayton and executed by A Salviati, was installed as a memorial to Thomas Brassey and his wife in 1879. Donald Insall Associates appointed Cliveden Conservation to repair and clean the damaged mosaic. Cliveden Conservation engaged with visitors, enabling them to witness ‘conservation in action’ and instructed volunteers with light cleaning of the wall mosaics in the north aisle of the Cathedral.

Summary of the conservation work carried out
The rainwater management system devised by Sir Giles Gilbert Scott for the chapel had caused the pointing of the external walls to fail and damage to the mosaic. Blisters and salts, due to the continual penetrating rainfall on the lower walls of the chapel, could be seen on the stonework inside and a fur of salt was present over most of the mosaic. Delamination of the fabric from the substrate meant large areas of the mosaic had been literally pushed off the wall.

Using transparent plastic sheeting, conservators made tracings of the designs to be replicated and reinserted for the missing and damaged sections before removing the delaminated mosaic areas. Areas that were already faced-up were cut and lifted away from the wall. Delaminating areas which had changed shape and held too much original mortar containing salts were broken down and the tesserae cleaned for reuse.

Using the tracings and original tesserae, conservators made replacement sections of the damaged and missing design. Where replacement or additional tesserae were required, new smalti, sourced to match the texture and tones of the originals, were carefully cut to size.

Edges of the areas that had been removed were checked and consolidated with grout. Hollow surrounding areas were also grouted. Where necessary, small holes were drilled and tesserae removed to allow for injection of pre mixed mortar. Walls were cut back and old fill was removed. Areas were brushed free of loose material.

A new bedding mortar was applied to the walls and mesh and tesserae sections were pressed in place. Joins and gaps were filled with additional tesserae. The areas were grouted using the same mortar material, then toned in with a wash of coloured acrylic paint. The mosaic was carefully cleaned to remove salt and grease.

Results
The mosaic was successfully repaired and cleaned.