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A New Water Separation Process for soil from Archaeological Excavations

Published online by Cambridge University Press:  23 December 2013

M. E. Weaver
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Extract

Early in 1970 David French asked me to try to find a solution to the problem of dealing with the large amount of very fine material which passed through his new archaeological sieving and flotation processes. The material was in fact graded from fine sand through silt to clay, and came from the end of the flotation boxes mixed with quantities of water. The resulting mud or slime then blocked up filters and overflows. Apart from the suspicion that one was thus missing very fine particles of archaeological interest, the discarded slime was slowing up and even threatening to stop the flotation processes.

The problem was thus one of separating quantities of very fine material from large quantities of water, and at the same time of separating fine organic material from particles of inorganic material–usually silicates.

Type
Research Article
Information
Anatolian Studies , Volume 21 , December 1971 , pp. 65 - 68
Copyright
Copyright © The British Institute at Ankara 1971

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References

1 The “Nipissing Mill Elutriator” is one of the “parents” of our new apparatus, and consisted of a series of three tinned conical vessels of increasing diameters. It was in use in 1914 to extract cobalt ore from slime at Nipissing Mill in Canada. This and many other early devices for ore dressing may be found in an extremely interesting volume which I would recommend to anyone working in this field—A Text-Book of Ore Dressing by Truscott, S. J., published by Macmillan & Co. Ltd., London, 1923Google Scholar.

2 Vide e.g. the Stokes formula for elutriation velocities for quartz particles, using Richards' constants for still water. The velocity of a particle falling in still water can expressed as follows:—

v = where v = velocity in mm per sec.

C = constant of 50 to 100. The lower for very flat particles (87 for quartz 100 for galena)

D = diameter in mm.

σ = density (water = 1)

3 Too high a velocity can cause delicate material in the water to be smashed against sieves, filters, or other collecting surfaces. This would defeat our object.

4 This other apparatus is described elsewhere but may consist of dry sieve shakers, a preliminary sorting and separating unit consisting of a partially irrigated table, followed by flotation boxes with 1 mm and ½ mm catchment filters. The basic field processing is completed by the “şeys”. The material collected from the “şeys” then goes through the process of sampling and preparation for laboratory examination.