China
Africa
Explore chapters and articles related to this topic
Analysis of Ancient Mosaic Images for Dedicated Applications
Published in Filippo Stanco, Sebastiano Battiato, Giovanni Gallo, Digital Imaging for Cultural Heritage Preservation, 2017
Filippo Stanco, Sebastiano Battiato, Giovanni Gallo
Mosaics are made of colored tiles, called tessera or tessella, usually formed in the shape of a cube of materials separated by a joint of mortar. The earliest known mosaic materials were small cones of clay pressed into wet plaster. Semi-precious stones such as lapis lazuli and onyx, as well as shells and terra cotta were also used. As the art developed, glass, ceramic, and stone tesserae were the most common materials, along with pebbles. Modernly, any small singular component can be used: traditional materials, glass or ceramic cast or cut into tiles, plus plastic, polymer clay (such as Sculpey or Fimo), beads, buttons, bottle caps, pearls, etc. The physical study of materials used in mosaics continues to be an active research field [10,17,38].
A note on the early thermographic approaches for the investigation of the Cultural Heritage
Published in Quantitative InfraRed Thermography Journal, 2023
S. Paoloni, N. Orazi, U. Zammit, P. Bison, F. Mercuri
In the late 1990s, IRT started to be also applied to the study of mosaics. A mosaic can be regarded as a multilayered structure consisting of surface tesserae, setting bed, plaster and a supporting ground. Variations in humidity and temperature values can lead to mosaic deteriorations and, in particular, to the detachment of the surface and sub-surface layers from the ground. In 1998, Spagnolo et al. carried out [31] some investigations in both a test sample and in a Roman-era mosaic hosted in the Hadrian’s Villa, Tivoli. Such studies were aimed at evaluating the effectiveness of an experimental approach including the combined use of Electronic Speckle Pattern Interferometry (ESPI) [32] and IRT for the non-destructive evaluation of mosaics. As regards the thermographic images that were recorded after the heating induced by the irradiation of two IR lamps, besides the contrasted features corresponding to internal defects, false indications originating from the presence of different coloured tesserae could also be observed. Owing to such a circumstance, the correct interpretation of the IRT images was considered not straightforward to obtain and, consequently, ESPI was regarded as a more reliable technique.
Features of light scattering on mosaic layers composed of structurally similar birefringent domains
Published in Journal of Modern Optics, 2020
D. D. Yakovlev, M. M. Sherman, A. A. Murauski, D. A. Yakovlev
Light scattering techniques are widely used in studying liquid crystalline (1) and polymer materials (2–4) and, in particular, structure formation processes in such materials (4). Often experimental conditions allow consideration of the problem of scattering of light on a liquid-crystal (LC) layer or a polymer film as the problem of diffraction of a light beam on a mosaic of tesserae (domains) with almost identical (similar) internal structure but different azimuthal orientation of elements of this structure. Such layers will be referred to here as quasiequidomain layers, and layers of tesserae having identical internal structure as equidomain layers. One of the most frequently used types of the equidomain layer is a locally uniaxial layer with the spatial distribution of the local optic axis of the form where ϕ(x, y) is the angle of the azimuthal orientation of the local optic axis; the z-axis of the reference frame (x, y, z) is perpendicular to the layer boundaries (5–7). In such a layer, the local optic axis is parallel to the layer boundaries at every point in the layer and its orientation is independent of z (Figure 1(a)). Such layers will be called simple mosaic birefringent (SMB) layers. SMB layers are often used as an optical model of fine-domain layers of a low molecular weight LC or LC-polymer material that exhibit the so-called schlieren texture (8,9) (the schlieren texture is a kind of optical pattern that is seen when the layer is viewed under a polarizing microscope with crossed polarizers; examples are given in Figure 1(a)). Such LC layers usually have no preferred azimuthal orientation of the local optic axis. Furthermore, the light scattering properties of the layer are often independent of its azimuthal orientation (optical statistical rotational invariance).
Mortar and Concrete: Precursors to Modern Materials
Published in International Journal of Architectural Heritage, 2023
The creation of this material is described by Pliny (1898 [c.77 CE]): Even broken pottery has been utilized; it being found that, beaten to powder, and tempered with lime, it becomes more solid and durable than other substances of a similar nature; forming the cement known as the ‘Signine’ composition, so extensively employed for even making the pavements of houses. Some confusion has since arisen regarding the naming of this material, and the terms ‘opus signinum’ and ‘cocciopesto’ are often used interchangeably to describe mortar which contains lime and crushed tile or pottery. However, this is at odds with the descriptions of ‘signinum work’ by Vitruvius (1914 [c.25 BCE]), which is specified for cisterns: Signinum work is made as follows. In the first place, procure the cleanest and sharpest sand, break up lava into bits of not more than a pound in weight, and mix the sand in a mortar trough with the strongest lime in the proportion of five parts of sand to two of lime.Further confusion occurs when comparing these definitions to those used within the field of mosaic conservation, where ‘opus signinum’ has been defined as a “pavement made of lime mortar mixed with ceramic fragments into which quadrangular tesserae or small stone fragments are inserted, either randomly or to form geometric designs,” and ‘cocciopesto’ as a “pavement made of lime mortar mixed with ceramic or stone fragments without the insertion of other elements” (Alberti et al. 2013). While the manufacture of pressing-room floors from broken pottery laid over a bed of lime was described by Cato (1935 [c.160 BCE]) prior to Vitruvius or Pliny, he gives no indication that this was done to produce any kind of chemical reaction or hydraulic improvement to the mortar and, instead, it seems this was done to produce a durable ceramic top layer which could be rubbed down to form a smooth layer.