Glass Kulinich Ekaterina, Ph.D, Chair of Silicate

Technology and Nanotechnology

Glass is a type of non-crystalline or amorphous solid. Glass generally refers to hard, brittle, transparent material. Examples of such materials include, but are not limited to:

soda-lime glass borosilicate glass acrylic glass sugar glass

In the technical sense, glass is an inorganic product of fusion

which has been cooled to a rigid condition without crystallizing

Glass in the common sense contains silica as the main component and

glass former, but silica-free glasses also exist

The amorphous structure of glassy Silica (SiO2). Long range order is not present, but we can see short-range order with tetrahedral arrangement of Oxygen (O) atoms around the Silicon (Si) atoms.

In the scientific sense the term glass is often extended to all amorphous solids (and melts that easily form amorphous

solids), including plastics, resins, or other silica-free amorphous solids

In addition, besides traditional melting techniques, any other means of preparation are considered, such as:ion implantation, and the sol-gel method. However, glass science commonly includes only inorganic amorphous solids, while plastics and similar organics are covered by polymer science, biology and further scientific disciplines

Glass plays an essential role in science and industry

The optical and physical properties of glass make it suitable for applications such as

flat glass, container glass, optics and optoelectronics material, laboratory equipment, thermal insulator (glass wool), reinforcement fiber (glass-reinforced plastic, glass fiber

reinforced concrete), art

Roman glass from the 2nd century

Roman glass found at Begram, Afghanistan, then part of the Greco-Bactrian Kingdom

The term glass developed in the late Roman Empire. It was in the Roman glassmaking center at Trier, Germany. Probably, the late-Latin term glesum originated Germanic word Glas for a transparent, lustrous substances.

Pure silica (SiO2) has a "glass melting point"— at a viscosity of 10 Pa·s - of over 2300 °C. While pure silica can be made into glass for special applications, other substances are added to common glass to simplify processing

Samples of fused silica

Sodium carbonate (Na2CO3) lowers the melting point to about 1500 °C in

soda-lime glass

However, the soda makes the glass water soluble, which is usually unnecessary, so

lime (calcium oxide (CaO)magnesium oxide (MgO) and aluminium oxide (Al2O3)are added to provide for a better chemical stability of glass

The resulting glass contains about 70 to 74 percent silica by weight and is called a soda-lime glass. Soda-lime glasses account for about 90 percent of manufactured glass.

As well as soda and lime, most common glass has other ingredients added to

change its properties

Lead glass (lead crystal, flint glass) is more 'brilliant' because the litharge (PbO2) increases glass shine

Boron may be added to change the thermal and electrical properties (Pyrex - borosilicate glass)

Adding barium increases the refractive index

Thorium oxide or lanthanum oxide gives glass a high refractive index and low dispersion. Such glass is used in production of high-quality lenses

Large amounts of iron are used in glass for infrared energy absorption (absorbing filters)

Cerium(IV) oxide can be used for glass that absorbs UV waves

Fining agents such as sodium sulfate, sodium chloride, or antimony oxide are added to reduce the bubble content in the glass

Borosilicate glass is a type of glass with the main glass-forming

components silica and boron oxideBorosilicate glasses are most well known for having very low coefficient of thermal expansion (~5 × 10-6 /°C at 20°C). Borosilicate glass is very resistant to thermal shock, much more than any other common glass

Borosilicate glass was first developed by German glassmaker Otto Schott in the late 19th century. After Corning Glass Works introduced Pyrex in 1915, it became a synonym for borosilicate glass in the English-speaking world

In addition to the quartz, sodium carbonate, and calcium carbonate traditionally used in glassmaking, boron is used in the manufacture of borosilicate glass

Typically, the resulting glass composition is about 70% silica, 10% boron oxide, 8% sodium oxide, 8% potassium oxide, and 1% calcium oxide (lime)

Borosilicate glass is use in chemical laboratory equipment, cookware, lighting, and in certain cases, windows

Glass container factories

Modern glass container factories are broadly divided into three parts:

-Batch house-Hot end-Cold end

The batch house is concerned with raw materials.

In the hot end are situated furnaces, machines that produce the containers (forming machines) and annealing ovens.

In the cold end – the aria for inspection and packaging equipment.

Batch houseThe batch house holds the raw materials for glass, primarily sand, soda ash, limestone, feldspar

These materials are received (typically by truck or rail transport) and elevated into storage silos. From the silos they are weighed out into a batch (charge) of several tonnes, using common glass batch calculation procedures. The batch is mixed and sent to silos over the furnace

Quartz sand (silica) as main raw material for

commercial glass production

Hot endFurnace

The hot end of a glassworks is where the molten glass is formed into containers. Batch is fed at a slow controlled rate into the furnace. The natural gas or fuel oil fired and operate at temperatures up to 1675°C. The temperature is limited by the quality of the furnace and by the glass composition

Forming processThere are currently two primary methods of

making a glass container – the blow and blow method the press and blow method.

In both cases a stream of molten glass at its plastic temperature (1050°C-1200°C) is cut by a shearing blade to form a cylinder of glass called a gob.

Both of the processes start whan gob is falling into the blank moulds. In the blow and blow process, the glass first is blown into the blank moulds to create a pre-container. This is flipped into a final mould, where a final blow make the final container shape.

In the case of press and blow, the pre-container is formed by a metal plunger which pushes the glass out into the blank mould.

Forming machines

The most widely used forming machine arrangement is the individual section machine (or IS machine). This machine has a bank of 5 -20 identical sections. The sections are in a row, and the gobs feed into each section via a moving chute, called the gob distributor. Sections make one, two, three or four containers simultaneously and the gobs fall into the blank moulds in parallel.

Annealing

As glass cools it shrinks and solidifies.

Uneven cooling causes weak glass due to stress. Even cooling is achieved by annealing.

An annealing oven heats the container to about 580°C then cools it, depending on the glass thickness, over a 20 – 6000 minutes.

Cold end

The role of the cold end is to inspect the containers for defects, package the containers and label the containers

Inspection equipment Glass containers are 100%

inspected; automatic machines, or sometimes persons, inspect every container for a variety faults. Typical faults include:

Small cracks in the glass called checks

Foreign inclusions called stones (pieces of the refractory brick fallen into the molten glass)

Other defects include bubbles in the glass called blisters and too thin walls

Lifecycle impact Glass containers are wholly

recyclable and the industry in many countries have a policy of a high price on cullet to ensure high return rates.

In Sweden, Norway, Denmark and Finland return rates is about 95 %. Return rates of less than 50 % are usual in other countries.

Colors

Colors in glass may be obtained by addition of coloring ions and by precipitation of finely dispersed colloides.

Iron(II) oxide give bluish-green tint and such glass is used for a beer bottles. Together with chromium it gives a more dark green color, used for wine bottles.

Sulphur together with carbon and iron salts produces amber glass from yellowish to almost black. In borosilicate glasses sulphur imparts a blue color. With calcium it provides a deep yellow color

Manganese can be added in small amounts to remove the green tint given by iron, or in higher concentrations to give glass an amethyst color. Manganese is one of the oldest glass additives, and purple manganese glass was used since early Egypt history

Black Manganese dioxide is used to remove the green color from the glass; in a very slow process this is converted to sodium permanganate, a dark purple compound. In New England some houses built more than 300 years ago have window glass which is light violet tint because of this chemical change

Selenium, like manganese, can be used in small concentrations to decolorize glass, or in higher concentrations to provide a reddish color, caused by selenium atoms dispersed in glass. It is a very important agent to make pink and red glass. When used together with cadmium sulfide, it yields a brilliant red color known as "Selenium Ruby"

Small concentrations of cobalt (0.025 to 0.1%) yield blue glass. The best results are achieved when using glass containing potash. Very small amounts can be used for decolorizing.

Tin oxide, antimony oxide and arsenic oxide produce an opaque white glass, firstly used in Venice to produce an porcelain imitation

Pure metallic copper produces a very dark red opaque glass, which is sometimes used as a substitute for gold in the production of ruby-colored glass

Nickel, depending on the concentration, produces blue, or violet, or even black glass. Lead crystal with added nickel have purple color. Nickel together with small amount of cobalt was used for decolorizing of lead glass

Chromium is a very powerful colorizing agent, yielding dark green or in higher concentrations even black color. Together with tin oxide and arsenic it yields emerald green glass.

Cadmium together with sulphur results in deep yellow color, often used in glazes. However, cadmium is toxic.

Titanium produces yellowish-brown glass. Titanium is often used to intensification of other colorizing additives

Metallic gold, in very small concentrations (around 0.001%), produces a rich ruby-colored glass ("Ruby Gold"), while lower concentrations produces a less intense red, often named as "cranberry". The color is caused by the size and dispersion of gold particles. Ruby gold glass is usually made of lead glass with added tin.

Uranium (0.1 to 2%) can be added to give glass a fluorescent yellow or green color. Uranium glass is typically not radioactive enough to be dangerous, but if ground into a powder and inhaled, it can be carcinogenic. When used with lead glass with very high proportion of lead, produces a deep red color

Silver compounds (notably silver nitrate) can produce a range of colors from orange-red to yellow. The way the glass is heated and cooled can significantly affect the colors produced by these compounds. The chemistry involved is complex and not well understood

Definition of glass Types of glass

Main components of glass Container glass production cycle

Color glass