Specification for Finished Glass Fabrics Woven From Rovings

This work is concerned with the effects of flow separation and surface nuclei on the operation of a fixed geometry Cavitation Susceptibility Meter (CSM) with laminar flow. Cavitation is induced under controlled conditions at the throat of a glass venturi tube for the measurement of the active nuclei concentration in water samples as a function of the applied tension. Both cavitation and flow velocity are monitored optically by a Laser Doppler Velocimeter. The throat pressure is determined indirectly from the upstream pressure and the local flow velocity. The results show that laminar flow separation and surface nuclei effects are the most stringent operational limitations. Separation in the diffuser increases the minimum attainable throat pressure above the susceptibility of most cavitation nuclei commonly found in technical waters. Surface nuclei can generate extensive sheet or spot cavitation at relatively high tensions even on optically finished glass surfaces. These phenomena are difficult to eliminate and bring therefore into question the practical utility of CSM’s with laminar flow and fixed geometry for the measurement of the dependence of the cavitating nuclei concentration over wide ranges of the applied tension, as required for cavitation studies.

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Semi-finished glass from Ile-Ife, Nigeria: implications for the archaeology of glass in sub-Saharan Africa

Antiquity ◽

10.15184/aqy.2020.77 ◽

2020 ◽

Vol 94 (375) ◽

Author(s):

Abidemi Babatunde Babalola ◽

Adisa Benjamin Ogunfolakan ◽

Thilo Rehren

Keyword(s):

Sub Saharan Africa ◽

Finished Glass ◽

Sub Saharan

Abstract

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The Glass Making Crucibles from Ile-Ife, SW Nigeria

Journal of African Archaeology ◽

10.1163/21915784-20180002 ◽

2018 ◽

Vol 16 (1) ◽

pp. 31-59 ◽

Cited By ~ 4

Author(s):

A.B. Babalola ◽

Th. Rehren ◽

A. Ige ◽

S. McIntosh

Keyword(s):

Raw Materials ◽

Compositional Analysis ◽

Refractory Clay ◽

Sub Saharan Africa ◽

15Th Century ◽

Southwest Nigeria ◽

Finished Glass ◽

Sub Saharan ◽

Glass Working

Abstract Crucibles to melt glass are very rare in archaeological contexts in sub-Saharan Africa. Recent archaeological excavations at Igbo Olokun, Ile-Ife (Southwest Nigeria) revealed abundant fragments of glass crucibles from 11th-15th century AD deposits, matching the complete and near complete examples earlier reported from Ile-Ife. This paper provides an in-depth examination of these crucible fragments in order to understand the material quality of the crucibles, their typology, and their functions in glass- working/making. Optical microscopic and scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS) analyses were carried out on ten crucible samples. The composition of ceramic fabrics and the adhering glass are presented and discussed in view of their function. The crucibles were produced from specifically selected highly refractory clay and used for melting glass from its raw materials; colorants were added to the melt in the crucible. The useable capacity of the crucibles varied from 1 to 7 liters, equivalent to about 2.5 to 17.5 kg of finished glass for each crucible. Compositional analysis of a sample of the thousands of glass beads from the excavations indicates that the crucibles were used to melt the glass used in the beads. Archaeological evidence of glass bead making at this scale has not previously been reported from West Africa. The crucibles are unique evidence of indigenous glass-working/making in Sub-Saharan Africa from early through mid-second millennium AD.

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