The use of ground glass in red glazes: structural 3D imaging and mechanical behaviour using optical coherence tomography and nanoindentation

In this study we investigate the impact of the addition of colourless glass particles to red glazes, as seen in many 15th-17th-century easel paintings. With the use of reconstructions, we examined the influence of the paint preparation process on the morphological and mechanical properties of the paint film. Three sets of reconstructions were made, a control without ground glass, reconstructions with coarse or fine ground glass mixed in, and reconstructions where fine ground glass was ground jointly with the pigment oil mixture. The latter gave the desired consistency and colour based on visual inspection. The dried reconstructions were non-invasively imaged using optical coherence tomography (OCT). A data-analysis pipeline was developed for both the segmentation of the OCT images and the measurement of the size and spatial distributions of the glass particles within the glaze layer. Moreover, we used a nanoindentation protocol to measure the viscoelastic properties of the dried red glaze film. The OCT results show an expected decrease in median particle size with longer grinding-time, for which the additional grinding with pigment/oil resulted in a more narrow size distribution and a homogenous spatial distribution of the glass particles. The nanoindentation results indicate that the addition of glass particles increases the elastic and viscous moduli of the red glaze layers. The homogeneous size distribution, obtained by grinding the oil, pigment, and glass together, induces higher elastic and viscous moduli. Our imaging and analyses approach, combining OCT and nanoindentation, provides a non-invasive and quantitative investigation of glass particles in (semi-) transparent paint layers, and their effect on the mechanical properties of the glaze. The results of this study contribute to a better understanding of the artists’ addition of ground glass in paint layers.

VITREOUS PROTECTIVE AND DECORATIVE COVERINGS ON WOOD PARTICLE BOARD

scientific and technological bases of receiving vitreous coverings on wood with use of a torch of low-temperature plasma are developed. Before plasma dusting of glass powders by grain structure 60-120mkm, the special protective coating protecting chipboard from destruction at high-temperature influence of a plasma stream on a front surface of the wood particle board (WPB) was applied. The structure of an intermediate protective coating including mix of a fine-grained glass powder and liquid glass is developed. Preliminary drawing an intermediate protective layer provides several consecutive technological operations. For receiving vitreous coverings fight of colored and colourless glass are used which was previously ground in spherical porcelain mills. Optimum process parameters of plasma dusting of glass powder on the front surface of chipboard are developed. Optimum parameters of plasma melting is: current - 800A; operating voltage – 30B, a consumption of plasma-forming gas of argon 2m3/h. Operational and aesthetic-consumer properties of vitreous protective and decorative coverings are investigated. It is established that vitreous protective and decorative coverings have the high durability of coupling with an intermediate protective layer. The received vitreous protective and decorative coverings on the basis of colored and colourless glass have the high water resistance, acid resistance, alkali resistance, as well as microhardness and high aesthetic performance. The technology is recommended for widespread industrial introduction.

Glass sand potentiality of bar sediments from Tista and Dharla rivers, Bangladesh

The present investigation deals with the glass sand potentiality of the barsediments of Tista and Dharla rivers from different locations of Nilfamari,Lalmonirhat and Kurigram districts, Bangladesh. Accordingly, fourteen sampleswere selected for grain size distributions with separation of magnetic minerals.Magnetic mineral content ranges from about trace amount to 0.06 wt%. Lightminerals separated by tetrabromoethane technique ranging from about 88 to 98 wt%. Moreover, glass sand as final products by flotation process evaluationranges from 58 to 80 wt%, which indicate good quantity of glass sand.Geochemical data also suggest that glass sands are suitable for commercial grade glass owing to its SiO2 content (80.7–94.1 wt%). In particular, the Tista Barrage site shows high SiO2 (94.1 wt%) with reasonably low Al2O3, TiO2, andMgO+CaO percentages, which suggest an excellent glass grade quality.Unfortunately, some impurities (e.g., Fe2O3, Zr) are comparatively higher thanstandards, which poses difficulties making high grade glass. However, if it ispossible to remove and/or decrease the major impurities, it may be used tomanufacture high grade glass (colourless glass).