Glass, What a Mysterious Substance It is.

How glass was called in Japan?
Giyaman from diamao in Spanish
Bowri Chinese origin
Ruri from vaidurya in Sanskrit
Biidoro from vidro in Portuguese
Garashi Used in Tottori and Shimabara provinces
Ga-su Used in Tottori province
Garansu Used in Iyo province

If you know of any other expressions, please let us know.

It is said that human beings first met with glass 5,000 B.C. So that human beings have been living with as long as 7,000 years. We think that handling glass is one of our life time works, and we are very happy to deal with the genuine article.

Definition of Glass (In a narrow definition):
 An Inorganic Substance available by cooling molten substances but not crystallizing them:
(1) It is not a crystal,
(2) Made from molten substances by cooling it, and
(3) An inorganic substance.

Under this definition, the fiber glass for optical communications is considered not to be a glass, as it is made by reactive evaporation from a vapor phase and is not a molten substance as shown in (2) above.

(In a Wide Definition): Non-crystal Solid State shows Glass Transformation phenomenon
1) Non-crystalline Solid
2) A Glass Transformation Phenomenon

Glass transformation means that if a glass material is heated or an supercooled liquid is cooled, it becomes a glass, and a sudden change in its thermal expansion coefficient and specific heat capacity at its melting point, or two thirds or one half of its liquid phase temperature. It can be said that glass is an supercooled liquid. (from the Glass Dictionary)

Mystery of Glass:

Why glass is transparent?

It is not so easy to answer that why glass (water, too) is transparent. Generally, a substance is a composition of a group of crystals, and each crystal has a boundary. For example, an aluminum oxide consists of particles whose diameter is in micron meter, where the wave length of visible rays are shorter than the diameter of the particles. So that visible rays are scattered by hitting the aluminum oxide particles, and appear to be a color in white. On the other hand, the particle of water is thousandth smaller than wave length of visible rays. Therefore, visible rays are not prevented from passing through water. Glass is made of oxidized silicon particles of twice as big as that of water where each particle is infinitely connected with no boundary at all. For details, refers to "garasu are kore" authored by Toyo Keizai Shinpou Co., Ltd.

(1) The particle of glass is much smaller than that of wave length of visible rays.
(2) No boundary due to infinite connection of oxidized silicon.

(l)Is Glass is Solid or Liquid?
It is a supercooled liquid. It does not exist in the natural world.
Few exceptions exist such as obsidian and meteorite glass.
(2) Why Glass is so Fragile?

Why it is so fragile?
Is there any method available to make a non-breakable glass?
Researchers have spent many years and found that the cause of such breakage is due to microscopic cracks on the surface of glass.

Break of glass means that the combination of silicon and oxygen is disintegrated.
But the power of such combination force is very strong.
In order to disintegrate such combination, a force of one(1) ton per square millimeter (likely a 10,000 ton vessel on a child's head) is necessary.
However, in the real world, glass easily breaks one hundredth of such force. This means that there are many microscopic invisible cracks on the surface of glass, and if a cracking force is concentrated to one of those cracks, it grows to a break force against the glass. Glass, a supercooled liquid, cannot prevent cracks from growing since it does not have any boundary while other solid structures have boundaries in crystal.
  • Glass is an Electrical Insulation Material
  • Glass is a Thermal Insulation Material
  • Glass dissolves in Water
    Glass slightly dissolves in water. When water drops on the surface of glass, the hydrogen ion in water and sodium ion in glass are exchanged and after the water is removed it remains on the surface of glass which is a different substance compared to inner construction of glass.
  • This is phenomenon is called:

    Blue discoloring An interference fringe color.
    White discoloring Deposits of Alkaline and Silicon oxide Tarnish of glass means
    this phenomenon

    Kinds of Flat Glasses Used for Generic Construction Works

    (1) Ordinary Flat Glasses

    a) Transparent Glasses Colburn and Fourcourt.
    b) Molded Flat Glasses Rolled out.
    c) Wire Meshed Glasses Roll-out Calendar.

    (2) Sheet Glasses Produced by the Floating Process

    a) Transparent Glass by the Floating Process
    b) Colored Glass by the Floating Process

    Colburn and Fourcourt Processes

    Flat glass productions by these processes are no longer used in Japan in these days.

  • Colburn Process
    Nihon Sheet Glass Co. used to produce sheet glasses by means of Colburn process since sheet glass can be pulled out horizontally which allows to have a longer gradual cooling span for producing soft and sticky glass sheets.
  • Fourcourt Process
    Asahi Glass Co. used to produce sheet glasses by this process. Since it pulls out the sheet glass vertically in a tall building, but the cooling process span is short and sheet glass becomes very solid and fragile. Its advantage over the other processes is to be capable of providing a plural number of glass pulling-out gates from a melting chamber.
  • Although these two(2) processes enabled to produce flat surface sheet glasses in certain extent, buffing processes were necessary for mirrors. Still some of foreign manufacturers are using these processes.

  • Floating Process
    It is an innovative flat glass production process invented by Pilkington of the United Kingdom.
    Utilizing the specific gravity difference between glass and molten tin as glass is lighter than molten tin, glass flows over the molten tin and glass itself is molten by a burner and the finished glass can be pulled out without any strain which can be used for mirror as is. In these days, this process is used through out the world.
  • Other Major Manufacturing Processes of Special Type Glasses

  • The Fusion Process
    The fusion, if translated into Japanese, is to indicate something molten, but this process enables to produce sheet glass by not touching impurities contained in the material of a melting chamber. Therefore the products are maintained at very high physical reliability.
    Its major usage is for liquid crystal displays. Especially, it is most suitable for color liquid crystal displays (Color LCD). In 1991, Corning Glass Works of the United States began to sell its products in Japan and is covering majority of market demands. The Nippon Sheet Glass Co. has been in development with Hoya Glass Co. and are supplying prototypes named Corning 7059NH. Its weak point is sometimes small bubbles tends to appear when two(2) sheets of glass are stacked together

  • Down Draw Process
    This process is good for volume production of thin glasses. Asahi Glass Co. is well known as a supplier of a 0.05mm thick glass used for the cover of solar battery. We are supplying a 0.2 mm thick cover glass for touch panel which is also produced by this process. Manufacturers who can supply this type of glasses are Corning Glass Works of the United States, DESAG, a division of Shott of Germany and Asahi Glass Co. of Japan. This type of glass is used for medical inspection, cover glass of microscope and touch panel for the displays
  • Re-draw Process
    This process is a secondary processing rather than a production process. The Down Load process referred to in the above requires highly advanced techniques as well as sophisticated facilities, therefore, this process features to pull out horizontally thicker glasses of 1.0 mm to 2.0mm by giving heat. Nippon Electric Glass Company's continuos re-draw process is one of the most sophisticated production facilities in Japan. It is capable of producing 0.1, 0.2, 03 mm thick glass sheets, etc. Use of such thin glass sheets are for Liquid Crystal Displays and Touch Panels.

  • Engineers in the field of electronics components are really interested in these glasses for more use in the future.
    A Glass Production Process does not employ heat melting:
  • The Sol Gel Process
    This process features to produce glass from a solution using sol gel change.
  • This process enables to produce glass at a lower temperature than conventional solution process.
    Since solution is not required to be heated at a very high temperature where crystallization occurs, a new composite glass can be produced which could never be produced by the conventional processes.
    Purification of the material is so easy, therefore, it enables to produce very pure glass. Researchers have been challenging to produce quartz glass and a compound glass made of inorganic and organic materials for contact lens.
  • Vapor Phase Deposition Process (CVD Process)
    This is a kind of quartz crystal glass production process developed by Corning Glass Works. At this point in time, a conduction loss of optical fiber of 0.2dB/km (Optical attenuation is one hundredth for 100 km) is accomplished.
  • Kinds of Glasses Classified by their composites:
    A) Soda Calcic glass (Soda Glass)
    B) Borosilicate Glass
    C) Lead Glass
    D) Other oxidized materials
    A) Soda Calcic Glass (Soda Glass)
    Soda Calcic Glass is quite easy to mold, superior in chemical resistance, the material is cheap and is commonly available. This is the basic glass historically as well as technically. It is used for sheet glass, bottles, etc.
    B) Borosilicate Glass
    A glass contains borax B203. Its important characteristics are low expansion coefficient and is chemically stable. In 1883, Shott first produced a new optical glass for correcting color aberration.

    a) A low expansion coefficient invented by Shott in 1883 whose expansion coefficient is approximately 60 x 10-7/degree C. As it has quite tough durability against thermal impacts, it was used for the windshield of gas lantern for street lights invented at that time set up a record of unprecedented sales volume and was used until Thomas Edison invents an incandescent lamp. It draws keen interests of engineers as the glass produced with new technology. Our touch-panel is one of merchandises using this technique.
    b) PYREX
    It was first developed by Corning Glass Works which was engaged in glass bulb production, then began to supply storage battery container railway signal system for Edison. In 1912, a borosilicate glass which has thermal coefficient of 36 x 10-7/degree C, then 1915, PYREX Oven Ware were began to sell as it withstands rapid heating as well asquick cooling.
    c) Glasses for Physical and Chemical Uses
    As the World War I began, supplies to the United States from Shott of physical and chemical use glass were suspended. It was proved to be a prototype glass development stage of PYREX whose code number 7740 that it was superior than the glass from Shott and Corning Glass Works began to supply it to the market.
    d) Neutral Glass
    This glass was first developed by Shott in 1910 for ampoule of injection as the hydrogen ion density in the ampoule does not change for a long period time, it was named then named neutral glass. Presently, ultra violet rays absorption glass for ampoule is also available.
    e) Glass for Electron Tube
    Tungsten, molybdenum and Kovar(28% Si, 17% Co, 54% Fe) are used for sealing electron emitting electrode of vacuum tubes. Borosilicate glass is used to seal such electrodes. Temperature coefficient of tungsten is 36 x 10-7/degree C, molybdenum is 55 x 10-7/degree C and Kovar is 50 x 10-7/degree C. These metals have similar temperature coefficient of borosilicate glass. If a halogen(F2, C12, etc.) is emitted, it deteriorates the material used for the cathode and reduces its thermal electron. As a general rule, a glass which does not contain halogen is used for electron tubes.
    For X-ray tubes, a Kovar glass is used which absorbs little X-ray.
    f) 96 % Silicon Oxide Glass
    In 1939, Corning Glass Works began to sell so called the Vycor, a High Silicon Oxide Glass (96% Si O2). Vycor has a similar temperature coefficient of quartz glass and is used for physical and chemical purposes, heat treatment dish of fluorescent substance, mercury lamp, and sterilizing lamp tube, which is a glass called the heat-resistant glass.

    C) Lead Glass for Optical Use
    a) Crystal Glass

    This glass is colorless and transparent and it looks like crystal is a lead glass which contains 24 % or more lead (Pbo) by weight, and it has a refractive index of more than 1.545% according to an international custom.
    b) Lead Glass for Optical Use
    This glass is used for lenses that require high refractive index and high dispersion.
    c) Lead Glass for Radiation Shield
    This glass is used for X-ray shield. Pilkington of the U.K. and Nippon Electric Glass are supplying this type of glass in Japan.
    e) Glass for Electronics Use
    Its crystalline flits are sealed with a funnel(funnel shaped glass) of CRT(Cathode Ray Tube) for the purpose of shielding X-ray. Its advantage over the other materials is to have a larger electrical resistance, and low viscosity and low specific heat coefficient which enables to process at a low temperature range, and low emission of gas as well. It fits for the use of bulbs and X-ray tubes due to its good ability to shield X-ray.
    D) Other Oxide Substance Glasses
    (1) Aluminosilicate Glass
    Features : * Expansion Coefficient 30~60 x 10-7/degree C. * Water-resistant in chemical endurance is extremely good. * Viscosity increases very rapidly as the molten glass temperature falls down, therefore, it is good for production of glass filament that requires short molding time. * Due to its softening point is more 900 degrees C, it is good for use where high temperature endurance is required. * A 25% higher than Soda Glass as far as stretch strength is concerned.

    a) The E Glass
    The E glass is an aluminosilicate glass which is produced largest in volume. It is used for FRP pipes.

    b) The S Glass
    It has a 33% higher stretch force and a 20% higher value of elasticity than that of the E Glass, which is used for engine case of rocket, etc.

    c) Glass Tube for Combustion
    Due to its very high maximum usable temperature, it is used for kitchen wares such as stove and percolator, high power electron tubes having very high bulb temperatures, and halogen bulbs.

    d) Photo Masking Glass
    This glass is used for drawing pattern of integrated circuit.

    (2) Borosilicate Glass

    a) Used for soldering glass due to its low melting point and is used for a bonding agent.

    b) For windowpanes of neutron shielding of nuclear reactor.

    (3) Orthophosphate Glass

    a) For artificial bones of bio-ceramics and root of permanent teeth. More and more use in the area of bio-ceramics are highly expected.

    b) Promising future in the area of optical electronic laser. It is already in practical use in the area of optical memories, for it shows a good violet ray penetration, measurement of gamma rays of X-ray, and absorption of near infrared ray.

    Shott and Corning Glass Works say that there are as many as 50,000 kinds of different composite glasses are available.

    * Ultrasonic Signal Delay Devices Made of Glass
    It is absolutely necessary for video cameras, video disks, and satellite TV's.
    A glass from Shott was first studied for radar use in 1940.
    * Faraday Rotation Glass

    It is used for light isolator for optical communications as well as laser nuclear fusion from now on.

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