In the right aisle of the north arm of the transept there is a late sixteenth-century altar with the marble altarpiece of Santa Tecla among the lions, made by Carlo Beretta in 1754. She was devoted to chastity and for this she was denounced as a Christian by her betrothed and condemned to be torn to pieces by lions. A lioness, however, stood between her and the beasts who spared her, crouching at her feet. This episode was portrait both on the altar and on the stained glass window of the Cathedral. The first cathedral built as such from the third-fourth decade of the century was dedicated to Santa Tecla. IV until its gradual demolition in the fifteenth century, completed in 1461, to make room for the Cantiere del Duomo, which at the time reached the first spans of pillars, beyond the transept.
The intervention from restoration was aimed at removing the widespread and tenacious deposit of particles present on all surfaces that totally obscured the colors of the stone, allowing to rediscover the delicate shades and to contrast the chromatic interference of the old grouting made of epoxy resin, now altered and chromatically changed .
We can summarize the operations carried out in:
Removal of inconsistent surface deposits with flat brushes and vacuum cleaner
Cleaning of the surface of the masonry by wet microaeroabrasivatura.
Removal where necessary of the resin used in the past to fill the joints between the segments
Chromatic balancing intervention to conceal the altered resin and restore correct readability to the masonry face
Cleaning of the statuary and the bas-reliefs of the altars with enzyme-based compresses (lipase)
Removal of processing residues with a steam generator
Surface protection with microcrystalline waxes