EVALUATION OF NEW AND OLD METHODS FOR CONSOLIDATION AND DESALINATION OF LIMESTONE CASESTUDIES; RENAISSANCE SCULPTURES IN LIMESTONE

Abstract

The thesis discusses the methods for consolidation of weathering limestone based on compatibility of consolidants with limestone. I base my essay on literary investigation, two case studies, and to some extend experimental work. The case studies represent two lunettes made by the sculptor Nicola Firentinac 1450-1500; Lunette on St: Ana Church, Island Hvar, Croatia and Lunette on St: Klara Church, Trogir, Croatia. This bachelor thesis discusses difficulties in decision making with slat laden reliefs in limestone and methods that can demonstrate effect of combined treatments; cleaning, desalination, consolidation and fills. The methods to be evaluated are: calcium hydroxide, barium hydroxide, ammonium carbonate, ammonium oxalate, new developments of nano-lime techniques, and alkoxysilanes. Except for the alkoxysilanes, which are important part of the discussion because of their wide usage and commercial availability, the methods discussed here can be considered as preventive measures. The experiment based on research of methods of consolidants' specific qualities and use is judged visually, with SEM (scanning electronic microscopy) and by water absorption. The tests which include water porosity on the untreated limestone, THEOS treated sample, and the penetration depth of barium hydroxide are performed on limestone from Gotland. The SEM results show that the penetration of barium hydroxide is directly proportional to the low porosity of the material and that the penetration is possible. Other methods have been judged visually or by microscopy. Due to the same nature of consolidate and substrate, SEM cannot distinguish between materials and provide any results for the methods using carbonates and oxalates. The tests also show that THEOS doesn’t influence hydrophobic behavior of limestone.