optics, glass

natural glass
- 黑曜石（英语：Obsidian）又名十勝石  Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock.^[4][5]

Obsidian is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth. It is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where the chemical composition (high silica content) causes a high viscosity which, upon rapid cooling, forms a natural glass from the lava.^[6] The inhibition of atomic diffusion through this highly viscous lava explains the lack of crystal growth. Obsidian is hard, brittle, and amorphous; it therefore fractures with very sharp edges. In the past it was used to manufacture cutting and piercing tools and it has been used experimentally as surgical scalpel blades. 

• Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. Obsidian is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth. It is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where the chemical composition (high silica content) causes a high viscosity which, upon rapid cooling, forms a natural glass from the lava.^[6] The inhibition of atomic diffusion through this highly viscous lava explains the lack of crystal growth. Obsidian is hard, brittle, and amorphous; it therefore fractures with very sharp edges. In the past it was used to manufacture cutting and piercing tools and it has been used experimentally as surgical scalpel blades.
• 在美國亞利桑那州所產的黑曜石称为「阿帕契之淚」，傳說阿帕契部落內的一支隊伍被敵方騎兵追到山上，50人死於第一波開火，剩下的25人選擇跳崖自殺，全軍覆沒，噩耗傳來，家人們痛哭的眼淚落到地上，變成了一顆顆黑色的小石頭，黑曜石因此得名「阿帕契之淚」。

raw material
-  Cerium nitrate refers to a family of nitrates of cerium in the three or four oxidation state. Often these compounds contain water, hydroxide, or hydronium ions in addition to cerium and nitrate. Double nitrates of cerium also exist.K₂Ce(NO₃)₅^[12] crystals can be grown by evaporating a solution of potassium nitrate, cerous nitrate, and nitric acid. Each cerium atom is surrounded by the oxygen atoms of five bidentate nitrate groups and two water oxygen atoms.^[6] It can be grown into optical quality crystals of around 100 cm³ in 12 weeks.^[6] Crystals are colourless.^[6] The space group of the crystal is Fdd2 and their form is orthorhombic.^[6] Potassium cerium nitrate was probably discovered by L. Th. Lange in 1861.^[13] However it was only properly described in 1894 by Fock. Even then the amount of water in the substance was wrong and it took till 1911 when Jantsch & Wigdorow correctly stated that there were two water molecules.^[16] The non-linear optical effects were found in 1993. For optical applications it is known as KCN.


The five big chains for ‏ sunglasses - Optica Halperin, Opticana, Erroca, Super-Pharm and Optic Doron
read more: http://www.haaretz.com/how-long-you-need-to-work-for-ray-ban-sunglasses-1.398176

ophthalmic hospital
- royal ophthalmic hospital

• missionary alfred hogg was trained at the hospital (where st pancras medical mission was located) before going to wenzhou
• is this the hospital? http://discovery.nationalarchives.gov.uk/details/r/81d4ed25-bf17-4193-8a1b-29fc614740e5

Glass casting is the process in which glass objects are cast by directing molten glass into a mould where it solidifies. The technique has been used since the Egyptian period. Modern cast glass is formed by a variety of processes such as kiln casting, or casting into sand, graphite or metal moulds.
- During the Roman period, moulds consisting of two or more interlocking parts were used to create blank glass dishes. Glass could be added to the mould either by frit casting, where the mould was filled with chips of glass (called frit) and then heated to melt the glass, or by pouring molten glass into the mould.^[1] Evidence from Pompeii suggests that molten hot glass may have been introduced as early as the mid-1st century CE.^[1] Blank vessels were then annealed, fixed to lathes and cut and polished on all surfaces to achieve their final shape.^[2] Pliny the Elder indicates in his Natural History (36.193) that lathes were used in the production of most glass of the mid-1st century.^{[citation needed]} Italy is believed to have been the source of the majority of early Imperial polychrome cast glass, whereas monochrome cast glasses are more predominant elsewhere in the Mediterranean.
- modern method

• Sand casting involves the use of hot molten glass poured directly into a preformed mould.^[5] It is a process similar to casting metal into a mould. The sand mould is typically prepared by using a mixture of clean sand and a small proportion of the water-absorbing clay bentonite. Bentonite acts as a binding material. In the process, a small amount of water is added to the sand-bentonite mixture and this is well mixed and sifted before addition to an open topped container. A template is prepared (typically made of wood, or a found object or even a body part such as a hand or fist) which is tightly pressed into the sand to make a clean impression. This impression then forms the mould.
• Kiln casting involves the preparation of a mould which is often made of a mixture of plaster and refractory materials such as silica.^[7] A model can be made from any solid material, such as wax,^[8] wood, or metal, and after taking a cast of the model (a process called investment) the model is removed from the mould.Pâte de verre is a form of kiln casting and literally translated means glass paste.^[7][12] In this process, finely crushed glass is mixed with a binding material, such as a mixture of gum arabic and water, and often with colourants and enamels. The resultant paste is applied to the inner surface of a negative mould forming a coating. After the coated mould is fired at the appropriate temperature the glass is fused creating a hollow object that can have thick or thin walls depending on the thickness of the pate de verre layers. Daum, a French commercial crystal manufacturer, produce highly sculptural pieces in pate de verre.
• Graphite is also used in the hot forming of glass. Graphite moulds are prepared by carving into them, machining them into curved forms, or stacking them into shapes. Molten glass is poured into a mould where it is cooled until hard enough to be removed and placed into an annealing kiln to cool slowly.

history
- ancient egypt
- roman empire
-  Murano is a series of islands linked by bridges in the Venetian Lagoon, northern Italy. It lies about 1.5 kilometres (0.9 miles) north of Venice and measures about 1.5 km (0.9 mi) across with a population of just over 5,000 (2004 figures).^[1] It is famous for its glass making. It was once an independent comune, but is now a frazione of the comune of Venice.Murano was initially settled by the Romans and from the sixth century by people from Altinum and Oderzo. At first, the island prospered as a fishing port and through its production of salt. It was also a centre for trade through the port it controlled on Sant'Erasmo. From the eleventh century, it began to decline as islanders moved to Dorsoduro. It had a Grand Council, like that of Venice, but from the thirteenth century, Murano was ultimately governed by a podestà from Venice. Unlike the other islands in the Lagoon, Murano minted its own coins. Early in the second millennium hermits of the Camaldolese Order occupied one of the islands, seeking a place of solitude for their way of life. There they founded the Monastery of St. Michael (Italian: S. Michele di Murano). This monastery became a great center of learning and printing. The famous cartographer, Fra Mauro, whose maps were crucial to the European exploration of the world, was a monk of this community. The monastery was suppressed in 1810 by French forces under Napoleon, in the course of their conquest of the Italian peninsula, and the monks were expelled in 1814. The grounds then became Venice's major cemetery. In 1291, all the glassmakers in Venice were forced to move to Murano due to the risk of fires.^[2] In the following century, exports began, and the island became famous, initially for glass beads and mirrors. Aventurine glasswas invented on the island, and for a while Murano was the main producer of glass in Europe. The island later became known for chandeliers. Although decline set in during the eighteenth century, glassmaking is still the island's main industry.穆拉諾（義大利語：Murano）是義大利威尼斯潟湖中的一個島。名義上是島，其實是群島，島與島之間由橋樑連接，形同一島。穆拉諾在威尼斯以北約1.6公里。穆拉諾以製造色彩斑斕的穆拉諾玻璃器皿而聞名於世，特別是拉絲熱塑。

Magazine
- http://www.gankyo.co.jp

https://www.quora.com/How-did-people-see-without-glasses-in-ancient-times-and-survive


event
- daegu international optical show, daegu metropolitan city