Egyptian faience glazing by the cementation method part 2: cattle dung ash as a possible source of alkali flux

Based on our current awareness, there are three distinct primary sources of alkali flux in the ancient Egyptian faience making: natron, soda rich plant ash and the so-called ‘mixed alkali fluxes’. Whereas the nature and origin of the first two types are identified to some extent, there are more questions regarding mixed alkali fluxes. In an attempt to provide further clarification on the latter source, a series of replication experiments on the production of Egyptian faience by the cementation glazing method were conducted using cattle dung ash as the source of alkali flux. After firing at 980 °C, the appearance of the faience objects, the microstructure and the chemical composition of selected samples obtained using scanning electron microscopy/energy-dispersive spectroscopy (SEM-EDS) were investigated. The discussion has primarily focused on cattle dung ash as the most, or one of the most, available sources of ash in ancient societies and its possible use as a source of alkali flux in the production of Egyptian faience, at least by the cementation glazing method.     

Suspended Equilibrium in Iran's Political System

Two sets of power relationships have emerged in the political system of the Islamic Republic of Iran: official, institutional relationships outlined in the Constitution, and unofficial, informal ones existing between and within groups and clusters of powerful individuals and institutions. The juxtaposition of informal factional alliances with the formal institutions of power has resulted in the development of a precarious balance within the state, as 'hardliners' and 'softliners' vie for greater influence and the adoption of their agendas as official state policy. The ensuing results have been two-fold. On the one hand, the emergence of multiple centers of power has enhanced the extent and reach of the state in relation to various social strata, thus bestowing it with considerable durability and staying power. On the other hand, the existence of multiple official and unofficial venues for competition has sharpened the tenor and substance of factional rivalries. For the most part, each of the factions has so far been able to balance out the influence and agendas of the other. At the same time, however, since the 'softliners' by and large advocate greater political liberalization, these very factional rivalries have had some modest consequences in opening up the Iranian polity. Ultimately, the pace and direction of political liberalization in Iran will depend on the outcome of the ongoing rivalry that is currently being played out within official state institutions and unofficial power-cliques.     

Experimental Study on Postponing the Deboning of FRP Sheets in Masonry Walls

ABSTRACT

A large number of buildings all around the world are constructed of unreinforced masonry. These structures do not act well during earthquakes because of their vulnerable behavior. In last two decades, fiber-reinforced polymers (FRPs) has been used widely in seismic rehabilitation and strengthening unreinforced concrete and masonry structures. One important issue in using FRP composites for strengthening masonry walls is the inopportune debonding of composites from the wall surface; thus, in this article new methods are proposed to further delay the mentioned debonding issue. For this purpose, 13 masonry panels with 100x870x870 mm dimension are strengthened by using carbon and glass FRPs (CFRPs and GFRPs). A variety of strengthening methods such as surface preparation, boring, grooving, nailing, and plaster are used to mount FRP composites to the walls. For each specimen subjected to diagonal compression test, the loading level along with tensile and compressive diagonal displacements are evaluated. In order to assess the effect of FRP composites, four unreinforced masonry walls are tested as well. The results show 110% increase in ductility index of reinforced specimens compared to the unreinforced ones.     

Egyptian faience glazing by the cementation method part 1: an investigation of the glazing powder composition and glazing mechanism

In cementation glazing, for various reasons, there are significant differences between the composition of the glass phases present in the faience microstructure and the glazing powder composition. Furthermore, in this glazing method, the glazing powder should perform more functions, which are: producing a shiny and smooth glaze coating, producing a firm capsule surrounding objects entirely (to prevent adhesion between sintered glazing mixture and the melting glaze coating), and, finally, producing a porous and friable sintered glazing mixture for safe and easy removal of buried objects. It is obvious that these functions also have significant effects on the glazing powder composition and constitution. Therefore, analytical data on faience glass phases are very unlikely to reflect the strict composition and constitution of the original glazing powder properly. Accordingly, the composition and constitution of cementation glazing powder have remained obscure for a long time. These data are particularly crucial factors for cementation replication experiments and, consequently, for our awareness of the ancient faience production. In this paper, a series of cementation replication experiments have been conducted in an attempt to provide further clarification of these issues. In addition, as a comparative indicator for alkali and copper vaporisation, a small piece of rock quartz was placed separately above the glazing powder. After firing, the appearance of the faience objects and quartz pieces and the microstructures and chemical compositions of a select group of samples, obtained using Scanning Electron Microscopy – Energy Dispersive Spectroscopy (SEM-EDS), were investigated. The discussion has focused mainly on issues such as the raw materials and their contribution in the glazing process, the criteria for determining the faience glazing methods, the necessary quantity of alkalis for a successful cementation glazing, and, particularly, the glazing mechanism.