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INTRODUCTION TO SAND CASTING
Although LOST WAX CASTING is a superlative method of reproducing detailed surfaces and intricate sculptural forms, premium materials and high labour costs makes lost wax a relatively expensive casting process - this is very much the case with larger scale sculptures in particular. Many monumental sculptures are made up of relatively simple forms and textures; these less detailed designs can often be reproduced by an efficient and economic alternative to lost wax casting known as SAND PIECE MOULDING or SAND CASTING.
Few (if any), art foundries specialising in sculpture casting operate a sand moulding process to the exclusion of lost wax casting; as such, sand moulding is generally practiced in parallel with lost wax casting [ref 1].
The tradition of sand piece moulding almost certainly owes it’s origins to the civilisations of Eastern Mesopotamia (circa 4000 BC). Through trading links with the Mesopotamians, it is likely that the early Egyptian metalworkers first acquired their skills in both lost wax casting and sand piece moulding – the evidence suggests that sand moulding was practiced in Egypt from about 2575 BC, and murals examined at archeological sites point to the use of advanced sand casting techniques in Egypt by about 1450 BC. Eventually the Egyptian’s metal-casting knowledge was passed on to (and had a significant influence on), the ancient Greeks who had themselves adopted a simple two part (BI VALVE) sand piece moulding technique by the 6th century BC [ref 2].
In general, the use of the lost wax technique for sculpture making in the West before the late 19th/early 20th centuries can probably be best described as patchy. It appears that despite the spectacular (Greek inspired), sculptural achievements of numerous 15th century Italian artists/craftsmen (Cellini, Ghiberti, Brunelleschi et al), many bronze sculptures cast between the end of the Renaissance and the onset of the twentieth century were in fact produced by one or another of the various sand piece moulding techniques available [ref 4 ].
In the case of the United States for example, lost wax art founding was not widely practiced until about 1900. The development of lost wax casting in the US can be attributed to the immigration of European founders during the late nineteenth and early twentieth centuries. Included among their number was the highly influential Italian craftsman, Riccardo Bertelli. Australia’s first professional art foundry was established by the British founder, Joe Lemon (at Moorabin in 1962), who originally trained at the Morris Singer in the UK (Peter Morley who later established the more enduring [lost wax] Meridian Foundry in Melbourne 1973 also began his career at Singers) [ref 3].
Given the now universal popularity of the lost wax technique for casting sculpture, the realatively recent reliance on sand casting for creating art works seems startling nowadays. However, it is important to bear in mind that many of the highly developed and refined materials available to the modern investment founder such as CERAMIC SHELL refractories and flexible polymer rubbers for example, were either totally unavailable or else uneconomic to use until relatively recent times (post 1960). An additional factor in the relative rarity of lost wax casting, is that a detailed understanding of how to successfully cast using fine investments lay with just a handful of (usually family) companies [ref 5 ]. These often patriarchal businesses typically took considerable care to restrict access to their skills and knowledge, effectively creating a ‘closed shop'.
In contrast to lost wax founding, which (in terms of technical development), had essentially remained static from the end of the 15th to the mid 20th century, sand moulding evolved dramatically with the onset of the eighteenth century – driven forwards by the imperative of the Industrial Revolution and an ever increasing demand for good inexpensive design, effective materials and efficient manufacturing methods.
In an observation on the methods of sculpture founding in Britain during the late nineteenth century, the founder G.G. Adams highlights the (then) importance of sand moulding.
“The modes of casting in bronze at the present day is totally different to that of the fifteenth century or earlier. We cut our figures into two or three pieces according to the design or form of the work; which are united and rivetted or burnt together as may be best according to our judgement. Sometimes we are enabled to cast an entire work [in sand]; but this is rarely possible in a statue unless modernised purposely or in a simple manner” [ref 6 ].
Using modern processed sands in combination with exceptionally efficient binders, it is now possible to cast relatively complex sculptural forms in sand, transposing detailed surface textures from master patterns into metal. Whilst it is feasible to cast a small scale artwork by sand piece moulding, this process is nowadays mostly used for the production of large scale monumental sculptures.
Throughout the long history of art metal founding, few truly monumental works have been cast using the lost wax process alone. Typically, sand casting and occasionally straight fabrication are preferred methods for creating large scale artworks in bronze. Both sand casting and fabrication are comparatively direct manufacturing techniques, both usually require fewer intermediate production stages than lost wax casting, thus offering a potentially significant saving on labour and materials. A good example of such a monumental work is the ‘Rochana’ statue, from temple of Todaiji (Japan 749 AD). This sculpture stands some 53 ft (15m) high, and contains an estimated 300+ tons of metal, with a cast wall thickness of up to 12 inches (300mm). During an address to the Society of Arts in April 1895, W. Gowland, a British expert on Japanese craft techniques, gave a description of the construction methods used to create the Rochana.
“It has not been cast in one piece, but is constructed chiefly of numerous pieces of comparatively small size. Some of the lower portions have been cast by building up the mould on the parts already finished, but the greater part of the image consists of separate casts which have been united by running in an alloy containing large portions of tin and lead between the edges” [ref 7 ].
Gowland’s observations illustrate the two basic techniques used to construct monumental artworks from sand piece moulds. The first method involves an ‘in situ’ sequential casting of the sculpture, typically this is enabled by the use of temporary furnaces, set in close proximity to the designated site. A refractory piece mould section is built on location, and the metal charge is tapped directly into the mould from a nearby furnace. The founder then moves on to construct the next adjacent mould section and so on until the design is completed – in a similar fashion to that of a builder laying down a series of continuous brick courses for a wall.
The second construction method involves the remote (workshop) casting of individual sections, these elements are later united on-site (in the example of the ‘Rochana’, this was done using a flow welding technique [see FINSIHING]). A ‘cast/fabrication’ technique of this type can be structurally supported by constructing a cast 'skin' over a fabricated sub-frame; this structure can also help to accurately guide the work’s fabrication phase. Nearly all modern cast sculptures made to a monumental scale are made by a foundry cast/on-site fabrication and installation method.
MASTER PATTERNS FOR SAND MOULDING >
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