Nambu Cast Ironwork Described below are the main stages in the production of one of the most representative pieces of this ironwork, a metal kettle. In all, there are more than 80 different production processes, beginning with the design and culminating with the finishing, all of which take approximately two months to complete. Ultimately, one of these kettles is a confluence of two craftsmen's work. One who makes the body of the kettle and the other who fashions the handle. This page uses QuickTime. To download click on the icon. Stage One Design: First of all, a sketch of the kettle is made. Generally speaking kettles are either round or flat in form but sometimes a kettle of an original shape is also made. Next, a section is drawn, from which to make the pattern. This is used to make the mold and nowadays, the patterns are made out of a piece of sheet metal, although in the past wood was used. There are three patterns. One each for the upper and lower halfs of the kettle, and another for the lid. The mold is made by rotating these patterns. In many cases, it is also necessary to make a pattern for the core, which fits inside the mold to produce the void in the casting. The difference between the pattern for the outside and the pattern for the core represents the thickness of the metal. Stage Two Making the Mold: First, river sand, clay and a clay slurry called hajiru are mixed together and put in a biscuit fired frame. The pattern is then fixed in the middle of the frame and rotated to make the mold. Three grades of river sand are added as the form is made. First of all, a coarse sand is used to produce the general form, and then the piece for the spout is added to the mold. Next, some clay is added to a fairly fine sand in order to perfect the shape. Finally, an extremely fine sand shaken through a piece of silk is used to produce the fine inner surface of the mold that will actually come in contact with the molten metal. Stage Three Click on the picture for QuickTime Movie Decoration, Texturing: Before the mold is completely dry, the surface is decorated. The most famous of the patterns used to decorate one of these kettles is known as arare and is a series of raised spots. Each one is made by pressing a shaped tool into the surface of the mold to produce some 3,000 individual raised spots. Besides such geometric designs, kettles are also decorated with raised designs of flowers and landscapes done with a variety of tools. One of the other features of this cast ironwork is the surface textures that can be produced. One is produced by sprinkling silk-shaken sand over the mold. For another, regular sand and clay are dissolved in some hajiru slurry and then applied to the surface of the mold with a cloth tampon. Alternatively, this mixture can be applied with a brush. Stage Four Making the Core: Following the same procedure, the mold for the core is made using a core pattern and then the mold is fired. To make a sand for the core, river sand and regular sand are fired and then any extraneous matter is removed. This "fired sand" is then mixed with some hajiru slurry. The two halfs (upper and lower) of the core are then made by pressing the specially mixed sand into the mold on a turntable. The two halfs are then joined with hajiru slurry and to evaporate any moisture in the core, it is dried in the sun. Stage Five Drying and Firing the Mold: Having thoroughly dried the two halfs of the mold for the body of the kettle, they are now fired for about two hours at a temperature of between 800°C and 1,000°C over a charcoal fire. Any fine cracks, which may appear, are dealt with using a brush or spatula. Next, the gate (the hole through which the molten metal is poured) is formed in the lower half of the mold. A gate is also formed in the mold for the lid to complete the work on the molds. The inside of the molds is then coated with lampblack to prevent the molten metal from adhering. Stage Six Assembling the Mold: The upper half of the mold is turned upside down and the core is placed inside. Then, two or three pieces of metal are placed on the bottom of the core to stop it moving (floating) and, when the molten metal is poured, they are absorbed by the hot metal. Finally, the lower half of the mold for the body of the kettle is placed on top. Stage Seven Click on the picture for QuickTime Movie Casting: The furnace, which is more than three meters in height, is fueled with coke and fed with pig iron, scrap iron and limestone to produce the molten metal needed for casting. The temperature of the furnace is raised to between 1,300°C and 1,400°C before all the ingredients are mixed. The molten metal is allowed to flow from the furnace into a special crucible and is then poured into the mold. Stage Eight Finishing: When the casting has cooled, the mold is opened and the piece is removed. The core is broken with a steel rod and any sand, which is attached to the inside surface, is cleaned off. Any flashing produced by gaps between the two halfs of the mold is removed with a metal hammer or file and after the shape has been perfected, the whole kettle is finished with a wire brush. Then, using a technique developed for the making of these kettles, the piece is exposed to the flame from a charcoal fire at a temperature of between 800 and 1,000°C. This is done to create an oxidized membrane and prevent rushing. Directly exposing the exterior of the kettle to a flame does, however, cause some unevenness in the finish. The oxidized membrane is therefore polished with such things as a wire brush to remove it to give the surface an even finish. Stage Nine Polishing, Coloring: Having first checked to see if there are any leaks, the kettle is now colored. In order to facilitate the easy application of the color finish, the kettle is heated to a temperature of 200°C over a charcoal fire. Then, while the kettle is being heated, a grass brush is used first to apply some natural lacquer to act as an undercoat. After this has been burned on, a solution made by adding iron rust to vinegar or tea is applied. Stage Ten Making the Handle: A smith forges a handle by hammering a piece of sheet steel, first to form a tube, which is then shaped, or fashions a handle from a steel rod. There are few smiths who can do this highly skilled work. Then, having colored the handle in the same way as the body, the handle is attached to complete the production process and the kettle.