Novel markers to early detect degradation on cellulose nitrate-based heritage at the submicrometer level using synchrotron UV–VIS multispectral luminescence

Cellulose nitrate (CN) is an intrinsically unstable material that puts at risk the preservation of a great variety of objects in heritage collections, also posing threats to human health. For this reason, a detailed investigation of its degradation mechanisms is necessary to develop sustainable conservation strategies. To investigate novel probes of degradation, we implemented deep UV photoluminescence micro spectral-imaging, for the first time, to characterize a corpus of historical systems composed of cellulose nitrate. The analysis of cinematographic films and everyday objects dated from the nineteenth c./early twentieth c. (Perlov's collection), as well as of photo-aged CN and celluloid references allowed the identification of novel markers that correlate with different stages of CN degradation in artworks, providing insight into the role played by plasticizers, fillers, and other additives in stability. By comparison with photoaged references of CN and celluloid (70% CN and 30% camphor), it was possible to correlate camphor concentration with a higher rate of degradation of the cinematographic films. Furthermore, the present study investigates, at the sub-microscale, materials heterogeneity that correlates to the artworks' history, associating the different emission profiles of zinc oxide to specific color formulations used in the late nineteenth and early twentieth centuries.