Technique for cleaning Tarragona miocene age dolomitized silty limestone, altered by urban pollution

Abstract

This paper reports the results of studies conducted to evaluate the most suitable cleaning technique for highly dolomitized, middle Miocene (Serravallian) calcisiltite from Tarragona, Spain, used to build Les Saleses Convent Church in Barcelona. This stone material was widely used in the decorative and sculptural details on Catalonian modernist buildings. On the church, as on most of the modernist buildings made of this material, the limestone was found to be greatly decayed, with highly reactive black crusts, soluble salts and disaggregation. The cause of these pathologies lay in both the surrounding environment and the original crystalline water-repellent coating applied to the stone surface. Based on the results of an analysis of the stone, the coating and the alterations, water-based procedures and chemical poultices were ruled out as cleaning methods. In subsequent testing, low pressure abrasive blasting and the localized use of laser techniques were found to yield good results. These two techniques were checked for effectiveness and their parameters were determined.

Keywords

• cleaning
• abrasive blasting
• laser