The restoration of the North Doors of the Baptistery carried out in the conservation laboratory at the “Opificio delle Pietre Dure”, directed by Marco Ciatti, equipped with a special mechanism which enables to rotate and support the two huge doors during conservation.
Each wing of the doors contains 14 panels, 37 friezes, and 24 little panels with heads of Profeths and Sibille. The panels and the friezes are gilded with the mercury amalgam technique and inserted with perimeter hammering.
This part of the project, started with Annamaria Giusti, is directed by Mariadonata Mazzoni with the technical direction of Stefania Agnoletti e Annalena Brini and collaboration of the project by Andrea Montanari.
The cleaning of the metal surface is conducted by eleven restorers graduated from the Opificio restoration school.
The cleaning of the bronze without gilding is carried out with various instruments and tools, such as scalpels and compressed air tools for taking away the incrustations and deterioration products. The gilding is cleaned with the laser ablation technique, a method studied for the Doors of Paradise with the collaboration of the National Council for Research in Florence.
The restorer undertaking cleaning uses the aspirator to extract all the volatile products of laser ablation, wears a mask and has adequate eye protection, the area to be treated is moistened with deionised water using a soft brush to reduce surface temperature.
For particular alteration the cleaning is integrated with the application of chemical poultices, thin needles are utilised to fragment thick concretion.
The various stages of restorations require great attention, the restorers work with magnifying lenses and have the support of the Scientific laboratory of the Institute where are studied the chemical compounds and the alteration present on the bronze and on the gilded surfaces as well as the alloy compounds.
After conservation the doors will be inserted into showcase with dried air. The restoration began on March 2013 is proceeding according to the time required thanks to the collaboration of the various professionals involved.