Metal Casting, Silverware, and Pottery Techniques
Metal Casting
Casting of Metals
Iron, known for its hardness and elasticity, cannot be worked directly (it requires rolling and merging). Various techniques are employed to create sculptures, including building (shaping iron with fire and a hammer). Two primary methods exist:
- Direct (forging, spinning): Striking hot or cold rods.
- Casting: Notably, the Lost Wax Technique.
Welding
Welding involves melting using an iron electrode on both surfaces, resulting in a strong and rigid union. Welding by contribution creates a structure similar to clay. Pig iron stove or plating (1836) is a process based on transferring metal ions from an anode to a cathode (negative to positive pole) in a liquid electrolyte of metal salts.
Silverware
Silverware, the art of working with gold, silver, and precious stones, is an ancient craft. It utilizes gold (ductile, malleable), silver (ductile, bright white, resistant to change except for oxidation), platinum, white gold, and ivory. Metals are often combined with stones:
- Precious: Diamond, ruby, sapphire, emerald.
- Semi-precious: Amethyst.
- Hardstones: Quartz, malachite, agate.
Glyptics, the artistic technique of stone carving, is commonly employed. Stones are often carved hollow (like seals).
Setting
Setting refers to how a stone is secured in a piece of jewelry. It aims to enhance the stone’s qualities. Setting forms include:
- Closed setting: Folding a sheet of metal around the stone, encircling it up to the girdle (edge).
- Claw or prong setting: Allows light to pass through the stone, maximizing brilliance.
- Invisible setting: A modern technique where the metal frame is hidden, giving the stone exceptional shine. It requires special preparation, with grooves carved into the stone’s bottom to accommodate a fine metal setting. Created by Cartier in 1917.
Another technique for working with gold is the lost wax method, used for creating figurines, similar to the lost wax casting process for sculptures. It was employed for crafting figurines that adorned bracelets and belts in the 17th century.
Embossing
Embossing involves working on metal sheets, resting them on a soft material.
Engraving in Metals
Initially, engraving was done with brushes, chisels, and punches.
Inlay Technique
- Damascene: Infiltrating threads of silver or gold onto iron or steel.
- Plating: Coating base metals with finer materials, such as gold or silver through electroplating.
Gold and silver works must be hallmarked to indicate their authenticity and the use of precious materials.
Forge
Forging is the art and the workplace of a blacksmith, who shapes metal using fire and a hammer. A forge typically includes a furnace (usually iron) for heating metals, an anvil, and a container for rapid cooling. Tools include tongs for handling hot iron and hammers for striking the metal. Forging shapes metal through plastic deformation, unlike processes that remove material (drilling, milling) or involve pouring molten metal into molds (casting).
Pottery & Enamel
Pottery involves creating three-dimensional objects where function dictates form, and decoration is secondary. Variations between spherical and cubic forms are often observed in relation to an axis. The clay mixture must contain plastic material (kaolin or clay) and non-plastic or flux (quartz, feldspar, silica sand). Plasticity allows for modeling and vitrification with fire. Clay types are categorized based on their firing temperature:
- Porcelain: After firing, it becomes impermeable, semi-transparent, and white. A mixture of kaolin, feldspar, and quartz, fired at high temperatures for extended periods. Often treated like sculpture, created by hand or on a lathe. Varnish adds color. Restoration is challenging.
- Earthenware or bisque: Fired at low temperatures, then decorated with glaze or slip. Made of clay. Biscuit refers to unglazed, matte porcelain or china. It differs from earthenware in its composition of kaolin, quartz, and feldspar.
- Engobe or slip: A viscous paste made by mixing dry clay with water, used for joining clay pieces.
- Grog: Clay fired at very high temperatures, then crushed and added back to clay. Used in raku (removing pieces from the kiln at 900°C and quenching them with water, creating a thermal shock that results in a thicker paste resistant to sudden temperature changes and unique colors due to the added chamotte stoneware). Raku and fireclay are popular in contemporary art.
Pottery Procedures
- Freehand: A complex technique, shaping clay into forms, used since ancient times and in contemporary ceramics.
- Mold: Used for replicating objects (plates, tiles), allowing for reconstruction through the mold.
Historically, a designated individual would assess the value of pottery pieces and mark them with a stamp indicating their place of origin. Today, many contemporary workshops are reviving this practice of marking their work.