Thangka
GENERAL DESCRIPTION
Thangkas are portable Tibetan religious paintings, which may be unrolled and displayed in monasteries or other religious contexts. They are painted in gouache on cotton backgrounds, with colors generally filling in patterns from stenciled underdrawings.
Anthracite
GENERAL DESCRIPTION
Anthracite is a variety of coal that has a high luster. It has the fewest impurities and is the least plentiful form of coal. Anthracite is similar in appearance to jet and is sometimes used as an imitation of a mineraloid.
Jet (lignite)
GENERAL DESCRIPTION
Jet is a dense, black, semi precious type of lignite that has a brilliant polish and is often used ornamentally. Considered to be a minor gemstone but not a true mineral, jet is a mineraloid. With an organic origin, jet derives from the extreme pressure decomposition of wood from millions of years ago. Found in two forms, hard jet is created by carbon compression and salt water, whereas soft jet is formed by carbon compression and fresh water.
Sancai
GENERAL DESCRIPTION
The sancai, or three color, technique is a hallmark of Tang dynasty (618-906 CE) clay sculpture. The colors were created by adding metallic oxides like iron and copper to lead glazes. The glaze was then splashed, streaked, and dappled over the surface of the sculptures.
Mercury
GENERAL DESCRIPTION
The chemical element mercury is toxic to humans. Early photographers used mercury as part of the daguerreotype process. It reacts with silver to produce the image.
Direct Positive (photography)
GENERAL DESCRIPTION
A photograph made without the use of a negative.
Steatite
GENERAL DESCRIPTION
Steatite refers to a very soft rock composed primarily of hydrated magnesium silicate. It is usually white, grayish green, brown, or in rare cases, red or black in color. Steatite is easily cut and has been used for carving objects such as bowls, boxes, figurines, beads, seals, amulets, and scarabs since ancient times. In modern construction, it is used for laboratory sinks, bench tops, and electrical panels.
Serpentine
GENERAL DESCRIPTION
Despite its marble-like appearance, serpentine is an easily carved mineral composed of magnesium silicate. Its coloration ranges from yellow, green, gray, brown, and black. Cultures since Paleolithic times have used serpentine for building and decoration.
Ambrotype
GENERAL DESCRIPTION
An ambrotype is a collodion negative on a clear glass plate with a backing of dark paper, velvet, or varnish. This dark backing reverses the negative's tones and makes it appear positive. Each is unique and cannot be reproduced. Ambrotypes were generally matted and presented in decorative cases.
Daguerreotype
GENERAL DESCRIPTION
Daguerreotypes are detailed and lustrous photographs on mirror-polished, silver-coated copper plates. The process produced a negative image in mercury deposits directly on the plate's silver surface. Sealing daguerreotypes under glass was necessary to preserve the delicate image and prevent the metal plate form tarnishing.