The ‘faience’ beads of the British Bronze Age have since the last century been appreciated as the product of a somewhat sophisticated technology. Although the possibility of local manufacture was seriously considered by earlier antiquaries, especially for the Scottish beads, in more recent years-since the writings of Childe and Piggott-a Mycenaean or Egyptian origin has been widely assumed for them.
Abstract Tests with the du Pont machine show that the practice of expressing abrasion test results as an abrasive index, i.e., abrasion-resistance relative to a standard rubber, does not enable different types of abrasive to be used indiscriminately because these are found to give widely different abrasive indices for the same rubber; thus, some abrasives may give four times as high an index as others. If attention is confined to abrasive papers, as distinct from bonded abrasive wheels, this variation is reduced, but is still large enough to be a serious factor in accurate work. It is clear that, even when this comparative method of testing is used, standardization of the abrasive paper is essential to reduce discrepancies between results obtained in different laboratories. Discrepancies will still exist, however, because abrasive paper is not uniform, and there is evidence that abrasive indices determined on different portions of the same paper may differ as much as those from different types of paper. To minimize the effect of this nonuniformity, two courses are open. (1) All the rubbers to be compared could be abraded on one and the same area of paper, preferably a large area to avoid wearing the surface, e.g., by giving each rubber a short run on each of the several paper discs used, instead of using a different disc for each rubber. (2) Different specimens could be tested on the two sides of the machine provided this has a pivotted arm. It is shown that this technique has several advantages. The factors that cause the abrasive index to vary from one abrasive to another are not known; it appears, however, that the degree of abrasiveness is not a determining factor. The two methods of calculating abrasion loss—as cc. per hr. and cc. per H.P.-hr.,—usually do not give the same abrasive index; in any standard test method it is therefore essential to state which is to be used. The variation of the abrasive index from one abrasive to another is the same whichever method of calculation is used.
ABSTRACTS A selection of faience beads has been examined using neutron activation analysis, with a view to distinguishing the provenance of individual specimens. Evidence is presented that the tin content in beads from British sites is significantly higher than in those from other areas. Characteristic features of beads from other sources are also discussed.
The attempts to understand the durability of glass are reviewed from the earliest studies in 1666, through the historical phases up to about 1960, followed by a summary of the recent investigations of the reactions that take place in the surface layers. Final sections are concerned with the recently discovered effects of surface damage and the problems of using glass as an encapsulating medium for the disposal of high-level radioactive waste.
Bibliography of papers bearing on conservation of painted glass. One hundred twenty nine entries. Recovery of lost faded decoration on painted glass. Use of the isoprobe for studying the chemical composition of some twelfth century glass from York Minster. A study of cleaning painted and enamelled glass in an ultrasonic bath.
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