New Materials and Advanced Procedures of Conservation Ancient Artifacts

1. Introduction

This Special Issue focused on scientific works on new materials and advanced procedures used in the preservation of ancient artifacts. It is known that cultural heritage assets, along with those of nature, represent the identity document of a nation. In the last 30 years, the science of preservation of ancient artifacts has increasingly established itself in research as a very attractive field, at the border between the two interdisciplinary areas of environmental science and engineering and that of materials science and technology. Two of the subfields of conservation science, preservation and restoration interventions, which required complex accounting studies between the new materials and application procedures with the old traditional ones, respecting the unanimously accepted rules of operation, led to obtaining, characterizing and elaborating of effective protocols of preserving, restoring and displaying the museum, which would allow it to be kept as close as possible to its original form since it was put into operation.

2. The Published Articles

The passage of time, through the action of environmental and human factors, through the lack of an adequate/firm preservation policy both for display and storage, often lead to damage with changes in the physical condition of the structurally functional elements and to the degradation of the component materials through the alteration of nature chemical. To stop the evolutionary effects of the exhibited artifacts, but also for the new ones discovered in the archaeological sites, with a precarious state of conservation, after determining the nature of the materials and the archaeometric characteristics, involving modern methods of investigation, in a system of coexistence or corroboration between interdisciplinary instrumental techniques, a series of compatibility studies, synergy and optimization of the preservation and restoration interventions are elaborated, respectively, and adequate protection measures are taken for display/storage, depending on the age, state of conservation, heritage value and typology/size of the artifacts.

In the first article [1], the authors studied a series of icons from the Monastery of Saint Mary, Techirghiol, Romania, which underwent some inappropriate restoration procedures, namely aggressive cleaning with metallic soaps that affected the pigments and binders based on egg and walnut oil. The microsamples of pictorial material were investigated by microscopic techniques (OM and SEM-EDX), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, wavelength-dispersive X-ray fluorescence spectroscopy (WDXRF) and gas-chromatography with mass spectrometry (GC-MS). Then, they were examined using optical microscopy (OM), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, wavelength-dispersive X-ray fluorescence spectroscopy (WDXRF) and gas chromatography with mass spectrometry (GC/MS) in good agreement with data from the literature. This study allowed the identification and quantification of the metallic soap, which generated deposits in the form of a white efflorescence, from the binding medium through oil polymerization of the metal carboxylate ionomer and the crystallization of saturated fatty acids. Six pigments (calcite, lithopone, carbon black, red ocher, vermilion and ultramarine) were identified, mostly affected by cleaning operations with triglyceride soaps, which led to the formation of encrusted, alveolar films, exfoliation, blisters and cracks of the pictorial layers. The obtained results allow the development of an experimental protocol for valorization through preservation-restoration.

The second paper [2] presents the authentication of a Stradivarius violin, “petit” type, model 1723, by correlating the structural–functional dimensional data with a series of archaeometric and chemometric characteristics determined by dendrochronological analysis and by three modern instrumental techniques (Microscopia Electronica de Scanning, coupled with X-ray Diffraction, µ-FTIR Spectroscopy and Thermal Derivatography in Dynamic Mode). The purpose of this study is to establish the structural–functional characteristics, the nature of the materials and their state of conservation in order to valorize, after restoration, as a collection artifact, similar to another study carried out by the authors. The violin is in a poor state of conservation, with the elements of the sound box cracked longitudinally (two large cracks extended on the top cover of the sound box, which runs through both loops and four cracks with vertical displacement at the level of the frets), along with a lot of damage (fractures and lack of material in the marginal area of the fillets, delays and tips, superficial scratches on the large loop, in the area of the jaw and the outer edge near the fillet) from handling both on the upper cover (front plate) and on the lower one (back plate). It has undergone varnishing/re-varnishing and restoration interventions with the opening and closing of the resonance box (removal and refitting of covers). On the screw, in the outer upper area, there are two cracks, one at the level of the hole for button 2 on one side and another at level 3 on the other side, resulting from handling, pressing and turning the button. On both verso and obverse, in the bow work area, the varnish is encrusted with extensive eroded areas. The violin is missing all structural and functional elements, only the head/snail with tongue, neck and tension knob centered on the end of the big loop is missing, the four keys/tension knobs, the fret, the mouthpiece, the string with the tuners, the saddle, the barber are missing with the holding clips and the four strings, plus the bow is missing). The violin is a 1723 model, small Stradivarius (1/2), built by an Italian luthier (possibly one of Antoniou Stradivari’s two sons), being a replica of the Stadivarius violins from 1721–1729. The leucometric characteristics of the label and the patina inside the resonance box are the basic elements that confirm the age of approx. 290 years. Through UV reflectography, the presence of gypsum, egg white and rosin was established in the preparation. The inner label is made of old paper on which the inscription is printed in black ink on two lines: “Antonius Stradivarius Cremonensis/Faciebat Anno 1723”, without the copyright logo; it is unframed and has evenly cut sides, with unfringed edges, the paper support of the label has an age patina with the degree of apparent whiteness corresponding to an age of over 290 years, and the printing ink is slightly embrittled, which demonstrates that the binder has slightly degraded, showing fine traces of cracking and expansion, without traces of microbiological contamination. Under the stereomicroscope, the inner surface of the sound box shows an easily legible age patina, which in the interwar period seems to have been cleaned when it was opened. The embedment of the counter-ecclesia is specific to the period 1721–1729. EDX and µ-FT-IR data correlate very well with those obtained by thermal analysis in dynamic mode, they highlight the presence in the structure of the wood (from the upper cover), hydrothermally treated in borax and alum solutions, for water, chemical and microbiological stabilization (insectofungic) and varnished for aesthetics and climate protection, in addition to cellulose and lignin and components from the preservation treatment and varnishing, representing the strong point of the authentication.

The following paper [3] focuses on an old Orthodox icon on a carved linden wood support, of particular beauty and ornamental and iconographic complexity, having a great heritage value, which required the development of an optimal preservation–restoration protocol for museum appreciation. It is made by an anonymous author and dated to the end of the 18th century and the beginning of the 19th century.

Initially, the nature of the painting materials was determined, and their state of conservation was evaluated, using OM, SEM-EDX, micro-FTIR methods and CIE L*a*b* colorimetry and visible and UV reflectography were used to evaluate the washing test and in compatibility studies. Based on the data obtained, the optimal materials and procedures were selected for structural reintegration (including support completions and filling gaps), then chromatic reintegration and polishing, followed by final revarnishing, with or without patina additives.

After aging, based on previous experiences, based on compatibility studies, a series of materials were chosen for cleaning systems of ingrained dirt, the preparation layer, the polychrome film, polishes and varnish, with which one of the authors performed the intervention preventive consolidation, and after cleaning, the definitive one, as then it was moved to chromatic reintegration, polishing and varnishing. In its final form, the painting was reintroduced into the museum circuit.

Another work [4] is devoted to the conservation of cultural heritage by taking measures to prevent degradation and damage caused by temperature and air humidity factors that are difficult to control. The objective of the research was to describe the museum microclimate and to identify and analyze the risk of degradation of museum artifacts to study the impact of indoor and outdoor hygrothermy on indoor microclimate parameters. In order to achieve the objective, the following were carried out: the acquisition of data on relative humidity and air temperature from inside and outside; the assessment of the museum’s load of artifacts and the transformation of data into quantitative and qualitative numerical measures of the risks of damage to the collections. In correlation with the structural and functional parameters of the museum, the working levels of the heating and air conditioning systems, the layout, the load and the typological complexity of the exhibited artifacts, were also taken into account in the analysis. The results obtained and analyzed against the background of previous experiences allowed us to develop a series of useful recommendations for stabilizing the climatic conditions inside the museum and to propose measures to mitigate the negative impact of the analyzed environmental factors.

A special place was occupied by work [5], which focuses on the study of an ancient artifact, type of ax with a copper disc, with a surface decoration made of a tin-based alloy, which was found east of the Mountains Carpathians in the Moldavian Plateau. According to previous studies, this is believed to be a unique piece belonging to the Middle Bronze Age of the Western Carpathian—Wietenberg, Suciu de Sus, and Ottoman–Füzesabony cultures. In order to evaluate the application process and the origin of the ores used, the variation of the concentration of chemical alloying elements in the surface and volume phase of the base alloy (copper) and of the ornament (tin) was determined with the help of optical microscopy (OM), stereomicroscopy (SM) and SEM-EDX electron microscopy. The archaeometric characteristics identified, as originating both during its use and during the period of lying in the archaeological site, were used in archaeometallurgical evaluations and in determining the state of conservation of the two components (axe and ornament), on the surface, interface and in stratigraphic section. Experimental data showed that, after being cast in porous silicon stone molds, the object was coated with a thin film by dipping in a readily fusible tin alloy material, which included copper as the main alloying component and arsenic and iron as minor components. After depositing this bright white ornamental layer, a beautiful decoration was applied to its surface by incision and engraving. The artifact was used as a battle ax, but it also had a rank function, because it belonged to a community leader. The data prove the ability of ancient craftsmen to design and process copper alloys to achieve authentic, extremely beautiful artifacts. Moreover, the work offers new possibilities to reveal the social and symbolic function of certain ancient bronze objects.

Another paper [6], compares the new hydro-stabilized wood from white elm and poplar, with samples from archaeological excavations, in order to elucidate the mechanism of the degradation processes and establish the state of conservation after recovery from the archaeological site. The archaeological elm was estimated to be ~350 years old, and the poplar ~1000–1200 years old. Analysis of the chemical composition of the archaeological samples showed significantly low holocellulose values, while the lignin, extractive and ash contents were considerably high, compared to the freshly cut samples. Fourier transform infrared (FTIR) spectroscopy also confirmed changes in the chemical structure of the elm and poplar archaeological samples. Through SEM-EDX electron microscopies they demonstrated that erosion bacteria were the main degrading agent in both the archaeological elm and the poplar, although hyphae of rot fungi were detected inside the vessel of the elements of the archaeological poplar sample.

The last paper [7] focuses on the study of the state of preservation of old documents on paper with inscriptions based on different types of ink, in an attempt to first determine the degree of damage and degradation and then to choose the best preservation solutions and restoration. The paper focuses on the analysis of three old documents exhibited at the “Poni-Cernătescu” Museum in Iași, Romania, which were analyzed by optical microscopy (OM), scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX), micro-FTIR and FT-Raman spectroscopy. Thus, based on the previous experiences of the group of authors regarding the morphology and chemical composition of writing paper and inks, the nature of the paper supports and the type of ink, as well as the crystallinity index of the cellulose, were determined. PCA (Principal Component Analysis) was also used over time by using spectral data collected by FTIR and Raman spectroscopy. Thus, the degree of degradation of the documents was established by corroborating with the other methods used and solutions were chosen for the preservation and restoration interventions.

3. Conclusions

In conclusion, this Special Issue has managed to collect high-quality papers on various applications in the science of conservation of ancient artifacts of cultural heritage, and we hope, based on the previous experiences of the collective of authors, by citing the most representative works published by them in recent years, to provide a solid state-of-the-art reference in this area of research.