Microscopic techniques (OM, ESEM) and a multianalytical approach (EDX, FTIR, XRD, TGA-DTA) to assess the fire damage on the painted stuccoes from the Petruzzelli theatre (Bari, Southern Italy).

The Petruzzelli Theatre in Bari (Southern Italy) is an important example of a nineteenth century "Politeama" (i.e. a venue intended for various forms of live entertainment) which was inaugurated in 1903. It was decorated with stucco elements, consisting of mouldings and decorations in greater or lesser relief present on the ceilings and walls, and on statues. In 1991 the Theatre was struck by a fire, which caused serious damage to the main auditorium, whose furnishings and roof were almost completely destroyed; the foyer was less badly affected, and a large part of the decorations (stucco, papier-mâché and wood) on the walls and ceilings remained apparently intact. On site examination by naked eye detected diverse forms of damage to the decorations ; both extensive blackening due to the presence of combustion deposits, and superficial "roasting", crumbling, cracks and separation of the stuccoes from the wall were observed in the areas affected by the flames. In contrast, in the areas furthest from the heart of the fire the damage appears to be basically due to the effect of high temperature fumes, with the presence of combustion deposits, underneath which the material seems intact. The present study aims at the characterization of the constituent materials and the painted surface decorations, as well as ascertaining the effects of the fire. It was carried out on the samples from the surviving parts of the stage-box decorations, directly affected by the fire, and on those present inside the foyer, affected by the fire to varying degrees. These stuccoes were compared with samples not affected by the fire, that were taken from rooms next to the Theatre. The composition and structure of the stuccoes and modifications related to the fire effect were investigated by Optical microscopy in transmitted and reflected light (LM) and ESEM, as well as by combined analytical techniques such as EDX DRX, FT-IR and DTA-TGA. The combined microscopic observations and analyses pointed out different types of stuccoes in terms of mineralogical-petrograhical composition. The effects of the fire action were identified in the formation of some new mineralogical phases, coming from the de-hydration of the gypsum binder, as well as from the mineral pigments used in the painted layers. Their presence allowed determining the different temperatures that were locally reached during the fire. Damage in the forms of microcracks affecting the stucco groundmass, detachments and melting of the superficial finishings were also observed, as well as micro-blisters likely due to the burning of the oil binder.