## 1 Introduction  
Modern restorers/conservatives need to know more about the remaining original portions of any work of art and understand how the piece of art has been treated over the years. Also, a major problem facing conservatives is caused by improper conservation treatments from the past [1]. The methods of art restoration used in earlier periods were closely linked to the techniques known at that time. Advances in science and technology and the development of conservation as a profession during the 20 th century have led to safer and more effective approaches to studying, preserving, and restoring objects. Modern conservation practice adheres to the principle of reversibility, which dictates that treatments should not cause permanent alteration to the object. Art conservation has become an important tool of research; it is a standard practice among professional conservators to document treatments with photographs and written reports [1, 2]. Thus, there is a real opportunity for science to further integrate into the preservation as well as restoration of modern art, especially in diagnosing art, because the appearance of a work of art reveals only its current state. Over the past few decades, the diagnosis of artworks has become less invasive thanks to the development of advanced non-invasive techniques, such as X-ray fluorescence (XRF) [3; 4; 5], Fourier transform infrared (FTIR) [5; 6; 7], and attenuated total reflectance Fourier transform infrared (ATR-FTIR) [8; 9] spectroscopy, or scanning electron microscopy (SEM) [10; 11], to enumerate only those methods that were used in the present study. These techniques can provide insight into the history of a work of art and evaluate previous interventions, which, in turn, can help with conservation and recovery efforts [12]. In many cases, the diagnosis will reveal the condition of a painting and may indicate its vulnerabilities. Sometimes, the diagnosis will reveal a '_pentimento_', or an early change of mind by the artist [13]. In other cases, the diagnosis reveals all the interventions of other artists or restorers who hide or destroy part of the original work. Depending on the philosophy of restoration, the work of art is preserved in its current state, restored to its original state, or left as a pastiche of old and new [14]. At the same time, cultural heritage is increasingly threatened by damage and even destruction from natural causes, as well as social and economic instability. In this regard, painted wood carvings or panels are very vulnerable to changes in the microclimate [15]. Before any restoration or consolidation, it is important to carefully examine the object to determine its current state of preservation with maximum precision so as to choose the most suitable treatments [16; 17]. Given the highlighted aspects, the assessment of the state of degradation of a work of art should be substantiated as a concept of mandatory diagnostic methodology. This must be materialized by a protocol based on the fusion of historical and stylistic data on the one hand and scientific data, which should include local microclimate conditions, the nature of aggressive agents, and their effects, on the other [18; 19]. The protocol must start from the knowledge of the materials used in the creative process, as well as in previous interventions, together with data based on historical and stylistic documentation about aggressors who have acted over time on the work of art. To determine the degree of degradation, it is necessary to establish a correct relationship between the microclimate and aesthetic changes. At the same time, the proposal for appropriate chemical reactions becomes a well-founded matter of the protocol. In addition, it is necessary to know in depth the details of alteration processes and accelerated aging on replica samples. Finally, one can choose the most appropriate complementary techniques to achieve the best results in the validation of restoration data, in a minimum time, and at a low cost, by providing accurate data and not approximate proposals.