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Spectroscopic techniques were carried out to identify the dyes used on the famous mediaeval Lady and the Unicorn tapestries kept in the Cluny Museum. Among the six tapestries, La Vue shows a colour variation between the front, which appears blue, and the back, which appears violet, on the Lady’s skirt. In the Middle Ages, it was common for the violet colour to be made with a blue dye bath (woad or indigo) followed by a red bath, which could be madder, cochineal, kermes, or orchil. Since orchil is known to be very unstable to light, its potential use in the original recipe was investigated and a study on this dye was performed. Contactless analyses (hyperspectral imaging in the visible-near-infrared range and UV fluorescence spectroscopy) were carried out on both the tapestry and mock-ups prepared following various mediaeval recipes. The investigation allowed for the identification of woad and orchil on the back of the tapestry, which was preserved from exposure to light. In addition, an ageing study elucidated colour degradation, revealing not only the different responses to light of different dyes but also the effect of specific dye preparations on light resistance. The experiments showed that the longer the maceration, the higher the light resistance of the dye. Furthermore, the red orchil colour fades faster than the woad.

Leye Cave (Dordogne, France) is a laboratory cave in the Vézère area, a region that contains some of the most famous rock art caves in the world such as Lascaux, Font-de-Gaume and Combarelles, and is listed as Human World Heritage by UNESCO. Leye Cave was selected because it is representative of painted caves, with respect to parameters such as its geological stage, the presence of water and carbon dioxide, the geological state of its walls, and the size of the cave. These wall states are studied to better understand the conditions of conservation of rock art caves without damaging them. The choice of an equivalent medium, i.e., a non-painted cave, was made to be able to conduct experiments or take measurements that would not have been possible in a rock art cave. The climatic conditions (temperature, hygrometry, etc.) monitored since 2011 are central to our understanding of the genesis and evolution of wall states. Leye Cave is sub-horizontal then descendant, forming a cold air trap. The phenomenon of condensation is thought to be important in the genesis of these wall states. Our article presents a model which describes the competition that exists between the conduction of the rock heating the air and the convection cooling the rock, in the area named the “Throne Chamber”, located in the deepest parts of the cave.

The aim of this research work was to conduct a comparative study on the effectiveness of the application of chemical cleaning versus laser cleaning in the removal of surface congruent dissolution products from a potash-lime–silica historical stained-glass sample. EDTA was selected as the chemical cleaning agent. Laser cleaning was performed using a 238 fs pulse UV (343 nm) laser. The comparative cleaning studies were carried out on a stained-glass piece supplied by the Maison Lorin Glass Restoration Workshop from Chartres, France. Given the complex nature, irregular thickness and heterogeneity of the encrustations found on the glass, the two cleaning approaches were carefully performed step by step, while monitoring the process using an optical microscope. Raman spectroscopy and field emission scanning electron microscopy were used to characterize the changes induced on the sample surface during the cleaning process. The results demonstrate that the two cleaning approaches were able to eliminate the outer surface dark layer associated with carbon compounds, as well as the external part of the white layer generated by the crystallization of salts, formed with the dissolved elements after a reaction with the air. A comparison of the advantages and disadvantages of each method is also presented.

The impact of wavelength and pulse duration in laser cleaning of hard blackish contaminants crust from archaeologically significant Pleistocene bone is investigated in this research. The objective is to determine the practical cleaning procedures and identify adequate laser parameters for cleaning archaeological bone from Sima de los Huesos (Spain) based on conservation and restoration perspectives. Bone surface cleaning was performed utilizing two Q-switched Nd:YAG lasers: sub-nanosecond pulsed lasers with emission wavelengths at 355 nm and 1064 nm, respectively, and a Yb:KGW femtosecond pulsed laser with an emission wavelength in the third harmonic at 343 nm. In all experiments, the laser beam scanning mode was applied to measure cleaning efficiency in removing contaminants and degradation products while assessing the underlying substrate surface damage. Several properties, including wavelength-dependent absorption, pulse repetition rate, and thermal properties of the material, are analyzed when evaluating the ability of these lasers to boost the cleaning efficiency of the deteriorated bone surface. Bone surface morphology and composition were studied and compared before and after laser irradiation, using Optical Microscopy, Scanning Electron Microscopy with Energy Dispersive X-ray Spectrometry (SEM-EDS), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Photoelectron Spectroscopy (XPS) characterization methods. The results indicate that 238-femtosecond UV laser irradiation with 2.37 TWcm−2 is significantly safer and more efficient toward surface contaminant desorption than sub-nanosecond laser irradiation. The results herein presented suggest that these types of fs lasers may be considered for realistic laser conservation of valuable historic and archaeological museum artifacts.

The site of Lalibela is the result of Tertiary volcanic activity which led to the formation of a vast outcrop of basaltic slag from which churches were carved. This reddish rock which is particularly suitable for carving, is extremely interactive with water. It was beneficial for the impressive excavation phases, but is now problematic for conservation purposes. Digging meant either the penetration of water into the massif and its erosion, but also the protection of the monuments from water stagnation. This is a very paradoxical situation in which water plays an alternately positive and negative role. Due to its sacred dimension, any intervention on the rock must be discussed and validated by the community. 3D technologies were used to carry out an assessment of the state of the site, to create a virtual 3D model that can be accessed and consulted remotely by all the specialists faced to the conservation problem; to trace the historical evolution of the site.

Abstract Controlled laser irradiation parameters using recently developed sub-nanosecond pulsed laser technology with emission wavelength in the near Infrared regime (1064 nm) have been assessed on a Pleistocene bone from the archaeological site of Sierra de Atapuerca, Spain. Burst pulse mode was employed to explore contaminant removal efficiency, while at the same time, assessing the degree of damage produced to the underlying original substrate surface. The surface morphology and composition of the deteriorated bone have been characterized, along with the effects of laser irradiation at 1064 nm, using Optical Microscopy (OM), Scanning Electron Microscopy–with Energy Dispersive X-ray Spectrometry (SEM–EDS), and X-ray Photoelectron Spectroscopy (XPS). The most effective laser cleaning parameters in burst mode have been identified in order to optimize the emission parameters of the laser, thus localizing its interaction within the outermost layers of contaminants and degradation products, avoiding damage to the underlying original bone surface. Hence, threshold cleaning and substrate damage values have been determined for this new sub-ns laser, paving the way to safer laser cleaning procedures that may be useful for the effective conservation of bone archaeological artifacts.

Stained-glass windows form an important part of cultural heritage. Short pulse lasers open new opportunities for safe decontamination. In this work, and for the first time, the interaction of sub-nanosecond and femtosecond pulsed lasers with some contemporary stained-glasses has been analyzed exploring their applicability to safely clean stained-glass windows. The results show that, in these materials, damage can be induced using energy levels below damage thresholds due to the heat accumulation in the coating layer that is being eliminated. The latter generates significant thermal stresses on the glass volume, which induce crack formation. In consequence, in order to apply safe stained-glass cleaning protocols, laser parameters have to be selected to control the temperature increase within this layer. To achieve the latter goal, two alternative irradiation procedures were explored in this work. As a first option, a reduction of the effective pulse repetition frequency to values lower than 20 kHz was applied. A second alternative was used for lasers with pulse repetition rates in the hundreds of kHz. In this case, the burst mode was employed controlling the number of pulses emitted and combined with an adequate time lapse selection between two consecutive burst runs. A proof of concept demonstration was carried out on a stained-glass sample from the Cathedral of Cuenca, dated at the end of the XV century. Resumen: Las vidrieras constituyen un elemento esencial de nuestro patrimonio cultural. Los láseres de pulsos ultracortos ofrecen nuevas oportunidades para desarrollar procesos de restauración seguros. En este trabajo, por primera vez, se estudia la interacción de láseres pulsados emitiendo pulsos en el rango de los subnanosegundos y femtosegundos con piezas de vidrieras contemporáneas, con el fin de explorar la posibilidad de desarrollar procesos seguros de restauración de vidrieras. Los resultados muestran que, en estos materiales, incluso trabajando con niveles de energía por debajo de los umbrales de daño, se puede generar deterioro por la acumulación de calor generada en la capa que se está eliminando, lo cual puede generar niveles de tensiones térmicas que provocan la ruptura del vidrio. Por tanto, para desarrollar protocolos de limpieza seguros, los parámetros de procesado deben escogerse de tal manera que se minimice la temperatura que se alcanza en esta capa. Se han explorado dos alternativas. Una es reducir la frecuencia de trabajo hasta valores por debajo de los 20 kHz. En el caso de láseres que trabajen a frecuencias más elevadas, la alternativa es trabajar en modo burst, limitando el número de pulsos en cada serie y estableciendo tiempos de espera entre dos series. Estas ideas se han aplicado sobre una pieza de vidriera de la Catedral de Cuenca de finales del siglo XV.

To the pre-Columbian Mochica culture, a culture that did not develop through writing, mural painting is a strong ideological vector that involves the implementers of those decorations and specialized craftsmen, as well as their sponsors, members of the ruling elite. Archaeometry allows us to answer questions regarding the pictorial technologies that were employed and to bring about pieces of information on the craftsmen who designed those decorations. A corpus of twelve samples of mural paintings has been analyzed in this study. They are from the ceremonial center of cultural and technological exchanges of San José de Moro (Mochica site of the Jequetepeque Valley), dated from the 8th to the 10th century (AD), where remains of mural paintings were uncovered in the alcoves of an elite entombment and on the interior walls of a huaca (Huaca La Capilla), a pyramidal building associated to worshipping. Analyses by SEM-EDS, X-ray diffraction and Raman spectroscopy were conducted on the samples, completing the analyses by portable X-ray fluorescence made in situ. The results obtained allowed us to chart part of the chaîne opératoire and to bring about pieces of information on ancient pre-Columbian craftsmen and their role in Mochica society.

One of the issues in archaeological sciences is the establishment of chronological sequences in areas of human occupation. The main objective in this context is the reconstruction of the cultural diachronic processes connected to the emergence, the evolution, and the vanishing of the material cultures connected to human societies in specific environments. Concerning the Mochica (2th-10th century, north coast of Peru), recent archaeological research is pursued in order to explain such processes. In this article, we propose a revision and a synthesis of the given information on the relative chronology of this culture. Moreover, we present an inventory of Mochica 14C dates obtained during the last forty years. Thus the goal here is to reassess the temporal and stylistical data accepted by the archaeological community.

An unusual dental deposit characterizes a skeleton from the excavation of the medieval graveyard at Clarensac (Gard, France). Its large size led us to investigate its origin, but the results of macroscopic examination alone are inconclusive. It could be either a biological formation such as tartar or a taphonomic process. To further our investigation, we carried out an analysis of the atomic composition of the deposit using a scanning electron microscope (SEM). This revealed the presence of atoms which are constituents of the inorganic portion of tartar. However, a post mortem calcification on a tartar deposit which was already present cannot be excluded. The existence of another example in the anthropological series studied, although smaller, indicates the importance of the loss of antagonist teeth in the development of such deposits.