GLASS AND GLAZING

common sense refers to a hard, brittle, transparent solid, such as that used for windows, many bottles, or eyewear

In the technical sense, glass is an inorganic product of fusion which has been cooled to a rigid condition without crystallizing.

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.

Glazing is a transparent part of a wall, usually made of glass or plastic (acrylic and polycarbonate).

Glass

Characteristics of Glass

No definite melting point, if heated it soften, melt and becomes a thick syrupy liquid making it possible to be bent.

While in a molten state, it can be blown, drawn, rolled, press and cast into a variety of shapes and textures.

Glass is commonly used to glaze window, sash and skylight openings in buildings.

(sometimes called window glass or drawn glass) was made by dipping a leader into a vat of molten glass then pulling that leader straight up while a film of glass hardened just out of the vat.

Sheet glass

The glass is taken from the furnace in large iron ladles, which are carried upon slings running on overhead rails; from the ladle the glass is thrown upon the cast-iron bed of a rolling-table; and is rolled into sheet by an iron roller, the process being similar to that employed in making plate-glass, but on a smaller scale.

Rolled plate glass

The elaborate patterns found on figure rolled glass are produced in a similar fashion to the rolled plate glass process except that the plate is cast between two rollers, one of which carries a pattern.

Figure rolled glass

is a sheet of glass made by floating molten glass on a bed of molten tin. This method gives the sheet uniform thickness and very flat surfaces. Modern windows are made from float glass. Most float glass is soda-lime glass, but relatively minor quantities of specialty borosilicate and flat panel display glass are also produced using the float glass process.

Soda-lime glass is prepared by melting the raw materials, such as soda, lime, silica, alumina, and small quantities of fining agents in a glass furnace at temperatures locally up to 1675°C.

The glass cools and slowly solidifies as it travels over the molten tin and leaves the tin bath in a continuous ribbon. The glass is then annealed by cooling in an oven called a lehr.

Float glass

Old window containing a sheet of float glass in the upper left section, Jena, Germany. The remaining sections are possibly not float glass as indicated by the distorted reflections of a tree.

A lehr is a temperature-controlled kiln for annealing objects made of glass.

is glass without internal stresses caused by heat treatment (ie by rapid cooling, or by toughening or heat strengthening). Glass becomes annealed if it is heated above a transition point then allowed to cool slowly, without being quenched.

Annealed glass breaks into large, jagged shards that can cause serious injury

Annealed glass

is a type of safety glass that holds together when shattered. In the event of breakage, it is held in place by an interlayer, typically of polyvinyl butyral (PVB), between its two or more layers of glass.

Laminated glass (safety glass)

(tempered glass) is a type of safety glass that has increased strength and will usually shatter in small, square pieces when broken.

Toughened glass is typically four to six times the strength of annealed glass.

Toughened glass

The term stained glass refers either to the material of colored glass or to the art and craft of working with it. As a material the term stained glass generally refers to glass that has been colored by adding metallic salts during its manufacture.

Stained glass

is a type of glass that has increased strength. The glass is chemically strengthened by submerging the glass in a bath containing a potassium salt (typically potassium nitrate) at 450 °C. 6-8x the strength of annealed glass.

Also unlike toughened glass, chemically strengthened glass may be cut after strengthening.

Chemically strengthened glass

Low-emissivity (Low-E) coatings are microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface primarily to reduce the U-factor by suppressing radiative heat flow.

Low-emissivity glass

The first self-cleaning glass was based on thin film titanium dioxide coating. The glass cleans itself in two stages.

Self-cleaning glass

Hydrophobic leaf surface

The 'photo catalytic' stage of the process breaks down the organic dirt on the glass using ultraviolet in sunlight (even on overcast days) and makes the glass hydrophilic (normally glass is hydrophobic). During the following 'hydrophilic' stage rain washes away the dirt - leaving almost no streaks, because hydrophilic glass spreads the water evenly over its surface.

or double glazing is a piece of glazing consisting of two or more layers of glazing separated by a spacer along the edge and sealed to create a dead air space between the layers. This type of glazing has functions of thermal insulation and noise reduction.

Insulated glazing

Glass brick, also known as glass block, is often used as an architectural element in underground parking garages, washrooms, municipal swimming baths, and other areas where privacy or visual obscuration is desired, while admitting light.