Laser and chemical cleaning tests for the conservation of the Porta del Paradiso by Lorenzo Ghiberti

Abstract In the framework of the preservation project of the Porta del Paradiso , carried on by the Opificio delle Pietre Dure of Florence, we investigated a cleaning methodology based on integrated chemical and laser techniques. This novel approach, which will replace the previous chemical protocol, was aimed at cleaning a number of gilded sculptural elements of the door frieze, without their being dismounted from the bronze framework. To such an end, optimised chemical and laser cleaning techniques were first singly investigated, and then integrated treatments were tested. The critical evaluation of each procedure was achieved through various diagnostic means to characterise the cleaned surfaces from chemical and physical points of view. The analysis demonstrated the various advantages of a laser-based treatment followed by light sodium potassium tartrate poultice application.