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Experiments in Egyptian Archaeology: Stoneworking Technology in Ancient Egypt
105. Before any experimental sawing and tubular drilling could commence, the most likely particulate abrasive material employed by ancient workers needed to be established. Emery and desert sand have been the subject of much discussion by Egyptologists and others.5 In this study, the archaeological and the environmental evidence, together with the results from these experiments,6 and those of other experimenters,7 were collectively assessed. The present experiments examined and evaluated the performance of the likely sawing and drilling abrasive under working conditions, and compared the results with the observed ancient sawing and drilling evidence.

108. Lucas rejected the use of emery, an impure variety of corundum, as there is no evidence of its occurrence in Egypt. Cyril Aldred33 and J.H. Breasted34 also supported the use of sand abrasive for cutting hard stone. Lucas rejected the use of emery, an impure variety of corundum, as there is no evidence of its occurrence in Egypt. He also rejected Petrie’s theory that for the drilling and sawing of the hard stones, jewelled points were set into copper tubes and saws. Petrie was unwilling to accept that sand could cut granite, stating that for cutting the soft alabaster, plain sand was amply hard, and that where alabaster vases had been cut, of the early dynasties at Hierakonpolis, and of Greek times at Memphis, large quantities of sand and alabaster dust had been found.35 J.E. Quibell and F.W. Green36 found sand that had been used as an abrasive material in a vase grinder’s workshop at Hierakonpolis; they dated this workshop to the Old Kingdom period.

109. Pliny, the Roman historian, stated: The cutting of marble is effected apparently by iron, but actually by sand, for the saw merely presses the sand upon a very thinly traced line, and then the passage of the instrument, owing to the rapid movement to and fro, is in itself enough to cut the stone.37

111. The lack of emery in Egypt, the existence of desert sand in vast quantities, the impracticability of mounting jewelled points into copper saws and drill-tubes, the finding of sand powders mixed with copper compounds associated with sawing and tubular drilling activities in both soft and hard stones, and the present experimental evidence, which shows that sand will grind very hard stones, including igneous varieties, all clearly point to sand being the primary source of the abrasive in use with copper saws and tubular drills. Craftworkers were able to supply tubes and saws with cutting teeth by the million, and the cost to the state was just the chore of collecting it. The actual use of the sand for grinding did, however, cause considerable damage to the health of craftworkers.

120. Two types of sand were obtained for the experiments. Measurements of 150 quartz crystals, from the first sand type, showed that their lengths fell between 0.69 and 0.16 mm. The second sand type contained larger crystals, and measurements of 100 of them revealed that their lengths mainly fell between 1.27 and 0.13 mm, except for a few crystals, whose lengths were slightly longer than 1.27 mm. The coarser sand was employed upon the granite and the diorite, the finer sand upon the hard sandstone, hard and soft limestone and calcite. (The results for soft limestone are included for comparison with the reed tube’s ability to cut this stone.) A large proportion of quartz crystals in sand are angular in shape, but an even greater proportion are roughly spherical. The angularity of quartz crystals proved to be an important factor in drilling and sawing the stones.

120. The sand abrasive in use for the Manchester sawing and drilling experiments was mainly utilized in the dry condition (Figure 4.8), but some tests were carried out with wet sand. In Aswan, one edge of the saw used wet sand to cut a slot in the rose granite, while the opposite edge of the saw used dry sand to cut a second slot. The large Aswan drill-tube used dry sand, but a short test with the sand wet revealed that this test, and the others, established that it is counter-productive to the type of sawing, drilling and boring undertaken by the ancient Egyptians. To our twenty-first century way of thinking, metal drills should be cooled by a mixture of water and soluble oil.
The experiments have demonstrated that problems caused by heat generated by friction do not arise, and quartz sand’s rate of cutting, particularly when used with metal tubes, is slightly better with the sand dry than with it wet. Measurements of the temperature of the test drill-tubes, under load for several minutes, showed a constant drill temperature of approximately 80–100°C.

122. The key factor enabling copper drill-tubes to operate is that individual quartz crystals embed themselves into the softer copper for a fraction of a second, and are swept around, or along in the case of a saw blade, the stone’s surface. The crystals striate the stone. These actions take place many times a second, causing a tubular-shaped hole (Figures 4.9, 4.10, 4.11), or a slot, gradually to be cut out of the stone. Work experience demonstrates that spherical sand crystals roll around and act as a form of bearing – similar to tiny ball bearings. These actions help the operators to turn a drill or to push a saw. However, at any one moment, larger, angular crystals are retained in the softer copper and are forced to striate the stone.

123. Wet sand is troublesome to work with inasmuch as that, when it is used up, that is, reduced to fine proportions, it is difficult to remove from a stone vessel. Used, dry sand may easily be poured out and fresh supplies immediately admitted. The essence of drilling with the sand abrasive is the continually smooth replacement of the worn crystals with new ones at the cutting face, and wet or drying-out sand prevents this. Very wet, or fluid, sand will interchange, but when considering deep holes in heavy sarcophagi, a new factor comes into play concerning the removal of the used sand from the hole. The tests showed that the sand, after being ground by the drilling action for some time, turns into a very fine powder. It has the texture of finely milled flour. Experiments have shown that if the quantity of sand in operation is ground until all the sand is turned into a finely ground homogeneous powder (Figures 4.14, 4.15), then a significant number of the particles are within the size range of 50 to 150 microns, with the odd particle measuring about 200 microns. Most of the particles are less than 50 microns in size. However, a further short period of grinding reduces the bigger particles to sizes lying between 50–80 microns (Figure 4.16). Some drilling of the stone still proceeds, even with this exceedingly fine powder. However, the powder, now exhausted as an effective abrasive for tubular drilling, can be used for polishing stone, for drilling stone beads and for making blue faience, frits and pigment.54

125. The powder, because of its fineness, is cohesive and sticks together in one mass, even though completely dry, remaining in position inside the drill-tube as it is withdrawn from the hole. The powder can, therefore, be withdrawn from deep holes in sarcophagi. Wet sand powder, owing to its weight and fluidity, cannot be withdrawn; it sinks to the bottom. Naturally, the tubular hole eventually becomes filled with used powder and further drilling operations are considerably frustrated.

127. The experimental drilling of the rose granite and the diorite produced lightgrey coloured powders. Black granite and basalt would produce darker grey powders; they may look and feel like powdered emery. Possibly, these darker grey quartz-based powders have mistakenly been identified as powdered emery. Powders from the drilling and the sawing of limestone and calcite are nearly white in colour, dependent upon the original colour of the sand abrasive. Anciently produced sand/stone/copper powders, a waste product, may well have been collected for use in other manufacturing operations: for the polishing of stone artifacts, for the drilling of the stone beads, and as a basic material for the manufacture of some faience cores, of blue and green faience glazes, and of blue frits and pigment. These matters will be investigated in Chapters 6, 8 and 9.

134.The experimental sawings of the rose granite with the wet and dry sand abrasive indicate that the stone was cut at roughly equal rates.

135. The drawbacks with wet sand are an increase in the effort to move the saw, the provision of the water and the consequential loss of the copper particles from the waste powders. On the other hand, dry sand can be used in locations far from water, an important consideration in Egypt. For dry sand, the ratios of the average weights of the copper worn from the Aswan tools to the average weights of the sawn and the drilled granite are similar to the results obtained from the Manchester sawing and drilling experiments. The Aswan sawing and drilling rates were respectively six and three times faster than the Manchester rates.

A Brief History of Drills and Drilling
7. An increase in drilling efficiency occurred in the Bronze Age, however, because of another important discovery, namely emery. With a Mohs' hardness of9, this material afforded a major increase in abrasiveness and was particularly effective on quartz (Mohs' hardness of 7). We have been able to document its use during the Middle Bronze Age, ca. 2,000 · B.C.E. (Gorelick and Gwinnett 1986), and suggest that the increased use of hardstones for beads, seals, and amulets stemmed from the awareness, availability, and use of emery as a loose abrasive.