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(Last modified August 2, 2001)
The question that is often asked is “can narrow-necked vases be made today?”. The answer of course is… yes. Narrow-necked vases are routinely made today with the same quality that is exhibited in ancient Egyptian stone examples. Most Egyptian stone vessels are made of carbonate rocks, sedimentary rocks, and to a lesser extent hard igneous rocks. The working of rocks like Egyptian alabaster (travertine), commonly used in ancient Egyptian vases, is quite easy because this rock is made almost entirely of the mineral calcite, which has an indentation hardness 30% greater than one’s fingernail, and 3 perfect cleavages making the mineral very susceptible to percussion carving. Hard rocks present more of a challenge, but are still made today with a high degree of quality. This is especially true for the lapidary carving of jade vessels, that have been made by the Chinese over the last 2000 years (for examples see: Hartman, 1969; Till and Swart, 1986). Nephrite, the main mineral constituent of Chinese jade, has a Mohs’ hardness of 6-6.5 and a very high mineral fracture toughness. The rock nephritic jade is one of the hardest rocks on the earth’s surface, much harder than diorite, and as a result jade cannot generally be carved by percussion and must be done by lapidary means. If it can be done in jade it can be done in diorite, anorthosite, and basalt since these rocks are mainly composed of the mineral feldspar, which has a Mohs’ hardness of 6-6.5, a fracture toughness which is very low, and the rock hardnesses of diorite, anorthosite, and basalt are less than that of jade, and can be carved by percussion. The hardest material in terms of indentation hardness that the ancient Egyptians worked into stone vessel was quartz (Lucas and Harris, 1962), which has a hardness about 10% that of natural diamond.
Today, narrow-necked vases, that is vessels with openings that have diameters smaller than the interior, are made by first drilling a central core to form a hollow shaft (figure 1). After the core is removed a tool is inserted into the hollow shaft to enlarge the interior by grinding, either by rotation of the tool or by a vertical up and down motion.
Any opening that is not extremely small will allow a lapidary tool to be angled into the interior for the purposes of widening it. The tool can be bent in order to fit into the opening, and it can be straightened out after it has been inserted. The Chinese today, used flexible wires made of soft iron and a slurry of silicon carbide for this purpose (figure 2a-b).
These tools wear out quickly and grinding is generally slow and tedious, a result of the need to remove a large amount of material from the interior of the vessel, and that the tools are usually not very efficient at this task. Another tool that is used by amateur lapidists, which is more effective, is a wire tool that utilizes a hinge pin and an elastic band (figure 3).
These tools can be powered by hand, a bow, or a machine tool. This principle can be used to hollow out even fairly large vessels with small openings. When stone vessels of this type are made today the lapidist will generally make them with fairly thin walls to reduce the weight of the object, and to produce craftsmanship that exhibits a graceful rather than clumsy effect (Long, 1976). When transparent rocks and minerals are used they should also have thin walls to allow light to pass through, of course the inside and outside walls must be polished. The inside polishing is not a particularly difficult task and involves using felt or other flexible lapping material, that can be inserted through the neck of the vase, and a suitable polishing abrasive. The following website demonstrates the making of Egyptian alabaster (travertine) narrow-necked vases by modern day Egyptian craftsmen with a grinding tool attached to a hand crank (Egyptian Crafts).
References
Hartman, J.M. (1969) Chinese jade of five centuries. C. E. Tuttle Co, Rutland, 172 p.
Long, F. W. (1976) The creative lapidary: materials, tools, techniques, design. Van Nostrand Reinhold, New York, 136 p.
Lucas, A. & Harris, J.R. (1962) Ancient Egyptian materials and industries. E. Arnold, London, 523 p.
Till, B. & Swart, P. (1986) Chinese Jade Stone for the emperors. Art Gallery of Greater Victoria, Victoria, B.C, 144 p.