The following description briefly outlines the stages of dhokra brass-casting as carried out by Dariapuri artisans today. Variations in materials and minor points of technique appear in other parts of the region, but the basic steps remain the same.
First a clay core is modeled to rough out the object. The core is smoothly finished but is without detail. In the case of, say, a rice measuring bowl, it will be a smaller undecorated version of the finished product. In other cases the core is a simplified version of the desired object. The cores for animal figurines, for example, usually have only rudimentary limbs; ears, tails and other anatomical and decorative details will be added later in resin.
In the second step, a “wax” made of slid tree resin, or other similar material such as paraffin or beeswax, is applied over the sun-dried core (Fig. 3). Since little work will be done to the cast piece except to brush off the mold and file or burnish it, every detail desired in the final cast piece must be present on the resin model. A resin strut attached to one end of the model will become the tube through which the molten metal is poured into the mold after the resin has been burned out.
When the resin model is finished, it is covered with several layers of slip-like clay and ash. This material must be both fine and porous so that it will faithfully reproduce in baked form the details of the resin model at the same time that it permits the heat to vaporize the resin through the mold. Then a more substantial clay mold is built over the inner clay layer (see Figs. 5, 6), and a flaring neck is built up to become the pouring spout for the attached crucible.
Unlike most other cire perdue techniques, the crucible used by the Dariapuris is not a separate container in which metal is heated and then poured out, but rather an intrinsic part of the mold itself, built up from the flaring neck at the top of the mold and filled with broken bits of brass. This bipartite mold is baked in a kiln to vaporize the resin and to melt the metal, then removed and rotated so that the metal can run down into the now hollow mold (Fig. 7). The mold is then set to cool, after which the finished article is broken out and wire-brushed to clean and burnish it (Fig. 8).
If no core is used and the model is a solid piece of wax or resin, the casting too will be solid metal. When the resin is built up over a clay core, however, the core remains inside the metal shell and may or may not be broken out. This kind of product is called hollow-cast, even when the core is left inside, as is the case in Dariapur. Hollow casting is conservative of metal (and therefore of fuel) and less tricky in terms of potential flaws and miscasts than is solid casting. Even with hollow casting, however, large pieces require more elaborate provisions, such as vents to permit gases to escape and chaplets to prevent the core from moving about within the mold. The Dariapuris do not ordinarily resort to these measures. Large or very complex pieces are usually cast in multiple parts and later soldered together.
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- Figure 3. A Dariapuri wraps dark resin strips around elephant-lamp models. Some artians make only a few kinds of objects. Others, like Haradhan, have a broad and inventive repertoire.
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- Figure 5. A woman covers headless elephant models with clay prior to baking. The heads, made separately, are joined to the bodies in a later step.
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- Figure 6. Molds in various stages of readiness dry in the sun.
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- Figure 7. A mold just out of the kiln is tipped so that the molten metal in one end can pour into the hollow impression in the other. Fellow artisans watch closely, ready to slap mud onto cracks through which red-hot metal might escape.
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Figure 8. A lidded container in the shape of an owl. Every detail of the original wax model has been faithfully captured in brass. This piece is one of the set cast in the Museum courtyard in 1986, and now in the Museum’s collections. Bits of the clay mold still cling to the owl’s feet.
Collection Object Number: 86-14-1a, b)
This article is an excerpt from The Brasscasters of Dariapur, West Bengal.