Agate is a common rock formation, consisting of chalcedony and quartz as its primary components, with a wide variety of colors. Agates are primarily formed within volcanic and metamorphic rocks. The ornamental use of agate dates back to Ancient Greece in assorted jewelry and in the seal stones of Greek warriors. Use of beads necklaces with pierced and polished agate goes further back to the 3rd millennium BCE in the Indus Valley Civilisation.
A mirror or looking glass is an object that reflects an image. Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse the direction of the image in an equal yet opposite angle from which the light shines upon it. This allows the viewer to see themselves or objects behind them, or even objects that are at an angle from them but out of their field of view, such as around a corner. Natural mirrors have existed since prehistoric times, such as the surface of water, but people have been manufacturing mirrors out of a variety of materials for thousands of years, like stone, metals, and glass. In modern mirrors, metals like silver or aluminum are often used due to their high reflectivity, applied as a thin coating on glass because of its naturally smooth and very hard surface.
The term stained glass refers either to coloured glass as a material or to works created from it. Throughout its thousand-year history, the term has been applied almost exclusively to the windows of churches and other significant religious buildings. Although traditionally made in flat panels and used as windows, the creations of modern stained glass artists also include three-dimensional structures and sculpture. Modern vernacular usage has often extended the term "stained glass" to include domestic lead light and objets d'art created from foil glasswork exemplified in the famous lamps of Louis Comfort Tiffany.
Cameo is a method of carving an object such as an engraved gem, item of jewellery or vessel. It nearly always features a raised (positive) relief image; contrast with intaglio, which has a negative image. Originally, and still in discussing historical work, cameo only referred to works where the relief image was of a contrasting colour to the background; this was achieved by carefully carving a piece of material with a flat plane where two contrasting colours met, removing all the first colour except for the image to leave a contrasting background.
Art glass is a subset of glass art, this latter covering the whole range of art made from glass. Art glass normally refers only to pieces made since the mid-19th century, and typically to those purely made as sculpture or decorative art, with no main utilitarian function, such as serving as a drinking vessel, though of course stained glass keeps the weather out, and bowls may still be useful.
Gilding is a decorative technique for applying a very thin coating of gold to solid surfaces such as metal, wood, porcelain, or stone. A gilded object is also described as "gilt". Where metal is gilded, the metal below was traditionally silver in the West, to make silver-gilt objects, but gilt-bronze is commonly used in China, and also called ormolu if it is Western. Methods of gilding include hand application and gluing, typically of gold leaf, chemical gilding, and electroplating, the last also called gold plating. Parcel-gilt objects are only gilded over part of their surfaces. This may mean that all of the inside, and none of the outside, of a chalice or similar vessel is gilded, or that patterns or images are made up by using a combination of gilt and ungilted areas.
Lead glass, commonly called crystal, is a variety of glass in which lead replaces the calcium content of a typical potash glass. Lead glass contains typically 18–40% lead(II) oxide (PbO), while modern lead crystal, historically also known as flint glass due to the original silica source, contains a minimum of 24% PbO. Lead glass is often desirable for a variety of uses due to its clarity.
Bangles are traditionally rigid bracelets which are usually made of metal, wood, glass or plastic. These ornaments are worn mostly by women in the Indian subcontinent, Southeastern Asia and Africa. It is common to see a bride wearing glass bangles at weddings in India, Bangladesh, Pakistan, Nepal, Sri Lanka and in other Asian countries. Bangles may also be worn by young girls and bangles made of gold or silver are preferred for toddlers. Some men and women wear a single bangle on the arm or wrist called kada or kara. In Sikhism, the father of a Sikh bride will give the groom a gold ring, a kara, and a mohra. Chooda is a kind of bangle that is worn by Punjabi women on her wedding day. It is a set of white and red bangles with stonework. According to tradition, a woman is not supposed to buy the bangles she will wear. Firozabad, Uttar Pradesh is India's largest producer of bangles.
Lampworking is a type of glasswork in which a torch or lamp is used to melt the glass. Once in a molten state, the glass is formed by blowing and shaping with tools and hand movements. It is also known as flameworking or torchworking, as the modern practice no longer uses oil-fueled lamps. Although lack of a precise definition for lampworking makes it difficult to determine when this technique was first developed, the earliest verifiable lampworked glass is probably a collection of beads thought to date to the fifth century BC. Lampworking became widely practiced in Murano, Italy in the 14th century. As early as the 17th century, itinerant glassworkers demonstrated lampworking to the public. In the mid-19th century lampwork technique was extended to the production of paperweights, primarily in France, where it became a popular art form, still collected today. Lampworking differs from glassblowing in that glassblowing uses a furnace as the primary heat source, although torches are also used.
Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion, making them more resistant to thermal shock than any other common glass. Such glass is subjected to less thermal stress and can withstand temperature differentials without fracturing of about 165 °C (300 °F). It is commonly used for the construction of reagent bottles and flasks as well as lighting, electronics and cookware.
Dzi bead is a type of stone bead of uncertain origin worn as part of a necklace and sometimes as a bracelet. In several Central Asian cultures, including that of Tibet, the bead is considered to provide positive spiritual benefit. These beads are generally prized as protective amulets and are sometimes ground into a powder to be used in traditional Tibetan medicine. Beads subject to this process have small "dig marks" where a portion of the bead has been scraped or ground away to be included in the medicine. Some dzi exhibit grinding and polishing of one or both ends, again the result of reduction for use in traditional Tibetan medicine or, in some cases, due to the bead's use as a burnishing tool in the application of gold leaf to thanka paintings or gilt bronze statuary.
Glass bead making is among the oldest human arts, with the oldest known beads dating over 3,000 years. Glass beads have been dated back to at least Roman times. Perhaps the earliest glass-like beads were Egyptian faience beads, a form of clay bead with a self-forming vitreous coating. Glass beads are significant in archaeology because the presence of glass beads often indicate that there was trade and that the bead making technology was being spread. In addition, the composition of the glass beads could be analyzed and help archaeologists understand the sources of the beads.
Venetian glass is glassware made in Venice, typically on the island of Murano near the city. Traditionally it is made with a soda-lime "metal" and is typically elaborately decorated, with various "hot" glass-forming techniques, as well as gilding, enamel, or engraving. Production has been concentrated on the Venetian island of Murano since the 13th century. Today Murano is known for its art glass, but it has a long history of innovations in glassmaking in addition to its artistic fame—and was Europe's major center for luxury glass from the High Middle Ages to the Italian Renaissance. During the 15th century, Murano glassmakers created cristallo—which was almost transparent and considered the finest glass in the world. Murano glassmakers also developed a white-colored glass that looked like porcelain. They later became Europe's finest makers of mirrors.
Ceramic glaze is an impervious layer or coating of a vitreous substance which has been fused to a pottery body through firing. Glaze can serve to color, decorate or waterproof an item. Glazing renders earthenware vessels suitable for holding liquids, sealing the inherent porosity of unglazed biscuit earthenware. It also gives a tougher surface. Glaze is also used on stoneware and porcelain. In addition to their functionality, glazes can form a variety of surface finishes, including degrees of glossy or matte finish and color. Glazes may also enhance the underlying design or texture either unmodified or inscribed, carved or painted.
A frit is a ceramic composition that has been fused, quenched, and granulated. Frits form an important part of the batches used in compounding enamels and ceramic glazes; the purpose of this pre-fusion is to render any soluble and/or toxic components insoluble by causing them to combine with silica and other added oxides. However, not all glass that is fused and quenched in water is frit, as this method of cooling down very hot glass is also widely used in glass manufacture.
Hardstone carving is a general term in art history and archaeology for the artistic carving of predominantly semi-precious stones, such as jade, rock crystal, agate, onyx, jasper, serpentinite, or carnelian, and for an object made in this way. Normally the objects are small, and the category overlaps with both jewellery and sculpture. Hardstone carving is sometimes referred to by the Italian term pietre dure; however, pietra dura is the common term used for stone inlay work, which causes some confusion.
Hedwig glasses or Hedwig beakers are a type of glass beaker originating in the Middle East or Norman Sicily and dating from the 10th-12th centuries AD. They are named after the Silesian princess Saint Hedwig (1174–1245), to whom three of them are traditionally said to have belonged. So far, a total of 14 complete glasses are known. The exact origin of the glasses is disputed, with Egypt, Iran and Syria all suggested as possible sources; if they are not of Islamic manufacture they are certainly influenced by Islamic glass. Probably made by Muslim craftsmen, some of the iconography is Christian, suggesting they may have been made for export or for Christian clients. The theory that they instead originate from Norman Sicily in the 11th century was first fully set out in a book in 2005 by Rosemarie Lierke, and has attracted some support from specialists.
Conservation and restoration of objects made of glass is one aspect of conservation and restoration of cultural heritage. The nature and varying composition of the material, and the variety of types of object made from it, demand certain specialized techniques. The conservator needs to be aware of "agents of deterioration" presenting particular risk to glass objects, and how to prevent or counteract their effects. Relevant education and training is available in certain countries through museums, conservation institutes and universities.
Ru ware, Ju ware, or "Ru official ware" is a famous and extremely rare type of Chinese pottery from the Song dynasty, produced for the imperial court for a brief period around 1100. Fewer than 100 complete pieces survive, though there are later imitations which do not entirely match the originals. Most have a distinctive pale "duck-egg" blue glaze, "like the blue of the sky in a clearing amongst the clouds after rain" according to a medieval connoisseur, and are otherwise undecorated, though their colours vary and reach into a celadon green. The shapes include dishes, probably used as brush-washers, cups, wine bottles, small vases, and censers and incense-burners. They can be considered as a particular form of celadon wares.
The conservation and restoration of ancient Greek pottery is a sub-section of the broader topic of conservation and restoration of ceramic objects. Ancient Greek pottery is one of the most commonly found types of artifacts from the ancient Greek world. The information learned from vase paintings forms the foundation of modern knowledge of ancient Greek art and culture. Most ancient Greek pottery is terracotta, a type of earthenware ceramic, dating from the 11th century BCE through the 1st century CE. The objects are usually excavated from archaeological sites in broken pieces, or shards, and then reassembled. Some have been discovered intact in tombs. Professional conservator-restorers, often in collaboration with curators and conservation scientists, undertake the conservation-restoration of ancient Greek pottery.
