Float Glass is a term for perfectly flat, clear glass (basic product). The term “float” glass derives from the production method, introduced in the UK by Sir Alastair Pilkington in the late 1950’s, by which 90% of today’s flat glass is manufactured.
Production: The raw materials (silica sand, calcium, oxide, soda and magnesium) are properly weighted and mixed and then introduced into a furnace where they are melted at 1500° C. The molten glass then flows from the glass furnace into a bath of molten tin in a continuous ribbon. The glass, which is highly viscous, and the tin, which is very fluid, do not mix and the contact surface between these two materials is perfectly flat. When it leaves the bath of molten tin the glass has cooled down sufficiently to pass to an annealing chamber called a lehr. Here it is cooled at controlled temperatures, until it is essentially at room temperature.
Clear glass is nearly colorless, and has a green or blue/green edge. When looking through the glass, as the glass gets thicker the faint green color becomes more noticeable and light transmittance drops. Ideal where high visibility and clarity are required.
Body-tinted glass is a normal float-clear glass into whose melt colorants are added for tinting and solar-radiation absorption properties. This reduces heat penetration in buildings. Colored glass is an important architectural element for the exterior appearance of facades. It is also used in interior decoration (doors, partitions, staircase panels, mirrors, etc).
Production: Its the same as in float glass production. The only variation is the colorants mixed at the beginning with the standard raw materials. Different additives may produce differently colored glasses.
Reflective glass is an ordinary float glass that has been treated with a metallic coating to allow it to reflect heat. It is not reflective in the sense that it acts as a mirror, although some products do indeed have a highly reflective surface, but rather in the sense that it reflects radiation rather than absorbing it. This type of glass is used in environmentally friendly construction with the goal of reducing heat gain and loss, making structures much cheaper to heat and cool over the course of the year. It is mainly used in facades.
Heat generated inside the building tends to stay in the building when the windows are made from reflective glass, which reduces heating costs. Conversely, heat from the outside stays outside, with the radiation being bounced back by the glass. This keeps the building cool in summer. Some structures that use it may be able to scale down or eliminate their climate control systems and other passive measures, while others need to run these systems less frequently, saving money and helping the environment out at the same time.
Mirrors are commonly made of glass with a smooth, polished surface that forms images by the reflection of rays and light.
They are exceptionally useful and practical devices and are commonly used in every area of daily life.
Production: The original method of making glass mirrors consists of depositing a coating of metal, mostly silver, on the surface of clear or body-tinted glass. A layer of copper, which is in turn protected by a painted backing, usually protects this deposit. The silver gives the mirror its reflective properties.
Insulating glass is a multi-glass combination consisting of two or more panes enclosing a hermetically-sealed air space. The most important function of insulation glass is to reduce thermal losses, which offers many advantages: lower energy consumption, perfect transparency by reducing the incidence of condensation on the warm air side and the possibility of using larger glazed areas without increasing energy consumption.
Production: Insulating glass is a glazed unit composed of two or more glass panes separated by spacers filled with dehydrated air or gas. The sheets are connected by a spacer, using sealants to reduce water vapor penetration. The whole unit is hermetically assembled by a secondary edge seal which gives structural robustness to the insulating glass. The spacer contains a desiccant which absorbs humidity from within the air space. The insulating glass unit (IGU) is made manually or with an automatic plant.
Acid-etched glass is produced by acid etching one side of float glass. Acid-etched glass has a distinctive, uniformly smooth and satin-like appearance. Acid-etched glass admits light while providing softening and vision control. It can be used in both residential and commercial settings (doors, shower screens, furniture, wall paneling, etc).
Patterned glass is a not-perfectly-smooth structure with different patterns impressed on it. The depth, size and shape of the patterns largely determine the magnitude and direction of reflection. Patterned glass usually transmits only slightly less light than clear glass. It can be used for a variety of applications: interior design and decorations, furniture, windows, street furniture etc.
Production: Patterned glass is made with a rolled glass process. The semi-molten glass is squeezed between two metal rollers. The bottom roller is engraved with the negative of the potter. Thickness is controlled by adjustment of the gap between the rollers.
Laminated glass is a combination of two or more glass sheets with one or more interlayers of plastic (PVB) or resin. In case of breakage, the interlayer holds the fragments together and continues to provide resistance to the passage of persons or objects. This glass is particularly suitable where it is important to ensure the resistance of the whole sheet after breakage such as: shop-fronts, balconies, stair-railings, roof glazing.
Production: There are two types of laminated glass: PVB and resin laminated glass:
- PVB laminated glass is two or more sheets of glass which are bonded together with one or more layers (PVB) under heat and pressure to form a single piece.
- Resins laminated glass is manufactured by pouring liquid resin into the cavity between two sheets of glass which are held together until the resin cures.
Tempered (toughened) glass is two or more times stronger than annealed glass. When broken, it shatters into many small fragments which prevent major injuries. This type of glass is intended for glass facades, sliding doors, building entrances, bath and shower enclosures and other uses requiring superior strength and safety properties.
Production: There are two different methods used to produce tempered glass:
- Heat treating: Where the annealed glass is subjected to a special heat-treatment in which it is heated to about 680°C and afterwards cooled. If it is cooled rapidly, the glass is up to four times stronger than annealed glass and its breaks into many small fragments (fully-tempered). If it is cooled slowly, the glass is twice as strong as annealed glass and the fragments of the broken glass are linear and more likely to remain in the frame.
- Chemical Strengthening: The glass is covered by a chemical solution which produces a higher mechanical resistance. Chemically-strengthened glass has similar properties to thermal-treated glass. The product is not generally used for window glass, but more commonly seen in industries where thin, strong glass is needed.
Wired glass is a product in which a wire mesh has been inserted during production. It has an impact resistance similar to that of normal glass, but in case of breakage, the mesh retains the pieces of glass. This product is traditionally accepted as low-cost fire glass.
Production: A steel wire mesh is sandwiched between two separate ribbons of semi-molten glass, and then passed through a pair of metal rollers which squeeze the “sandwich of glass and wire” together.
Insulated glazing more commonly known as double glazing (or double-pane, and increasingly triple glazing/pane) are double or triple glass window panes separated by an air or other gas filled space to reduce heat transfer across a part of the building envelope.
Insulated Glass Units are manufactured with glass in range of thickness from 3mm to 10mm or more in special applications.
Laminated or tempered glass may also be used as part of the construction.
Most units are manufactured with the same thickness of glass used on both panes but special applications such as acoustic attenuation or security may require wide ranges of thicknesses to be incorporated in the same unit.
A curtain wall system is an outer covering of a building in which the outer walls are non-structural, but merely keep the weather out and the occupants in. As the curtain wall is non-structural it can be made of a lightweight material, reducing construction costs. When glass is used as the curtain wall, a great advantage is that natural light can penetrate deeper within the building. The curtain wall faÃ§ade does not carry any dead load weight from the building other than its own dead load weight. The wall transfers horizontal wind loads that are incident upon it to the main building structure through connections at floors or columns of the building. A curtain wall is designed to resist air and water infiltration, sway induced by wind and seismic forces acting on the building, and its own dead load weight forces.
Curtain wall systems are typically designed with extruded aluminum members, although the first curtain walls were made of steel. The aluminium frame is typically infilled with glass, which provides an architecturally pleasing building, as well as benefits such as daylighting.
Structural glass walls overcome the restrictions of conventional frames to provide the ultimate all glass faÃ§ade. They use proprietary mechanical fixings and toughened safety glass and combine strength and visible lightness to provide high performance window faÃ§ade systems.
Structural glass is secured to a support structure by a variety of fitting options which are designed to meet the unique requirements of the project. These fixings absorb forces when the glass flexes under load and provide a secure connection between the glass component and the support structure.
Structural glass wall design can be complex and depend on design loads, seismic movements, support structure and glass support method.
Low E Glass
Low-emission glass (low thermal emissivity or low-e glass as it is commonly referred to) is a clear glass, it has a microscopically-thin coating of metal oxide. This allows the sun’s heat and light to pass through the glass into the building. At the same time it blocks heat from leaving the room, reducing heat loss considerably.
Low-e glazing units can make your home more than twice as energy-efficient in comparison to double glazing with no low-e coating. It is essential for rooms or buildings with a high proportion of windows or glass doors, such as conservatories and sun rooms.
During cold weather, the heat from your home is protected and sealed inside. During warm weather, the heat outdoor heat is prevented from entering your home.
Production: On-line coated (pyrolitic process): this is a clear glass which has been coated with a metal oxide through pyrolysis when the glass leaves the tin bath (at 650°C). The coating is therefore very resistant to mechanical damage, and this Low-E glass can be cut, tempered or laminated just as normal uncoated glass.
Off-line coated (magnetron process): is a clear glass which has received, on one of its faces, a silver coating applied by magnetically-enhanced cathodic sputtering. This type of Low-E must be used exclusively in insulating glass, with the coating on an internal face. It can be tempered and laminated.
U value is a measure of heat loss in a building element such as a wall, floor or roof.
It can also be referred to as an overall heat transfer coefficient and measures how well parts of a building transfer heat. This means that the higher the U value the worse the thermal performance of the building envelope.
A low U value usually indicates high levels of insulation.
They are useful as it is a way of predicting the composite behaviour of an entire building element rather than relying on the properties of individual materials.
Enameled/Screen printed glass
Enameled glass is tempered or heat-strengthened glass, one face of which is covered, either partially or totally, with mineral pigments. In addition to its decorative function, enameled glass is also a solar ray controller. Enameled glass is used for glazing and for cladding in facades and roofs. It can be assembled into laminated glass or glazed insulation.
Production: Enameled glass is produced by depositing special mineral pigments on the glass surface which vitrify at the annealing or tempering temperatures. This is a stable, non-biodegradable deposit, and can be made in one or more colors, and in different figures (tips, letters, pads).
Antique glass is a decorative silvered glass mostly used for interiors. This method of making glass consists of varying the regularity of metallic deposits. In addition to its decorative effect, the antique mirror creates a gentle and softened reflection, which contributes pleasantly to interior light levels.
Photovoltaic glass is a special glass with integrated solar cells, to convert solar energy into electricity. This means that the power for an entire building can be produced within the roof and faÃ§ade areas.
Production: The solar cells are embedded between two glass panes and a special resin is filled between the panes, securely wrapping the solar cells on all sides. Each individual cell has two electrical connections, which are linked to other cells in the module, to form a system which generates a direct electrical current.
X-ray Protection Glass
X-ray protection glass is an amber-colored glass containing 70% lead oxide, which significantly reduces ionizing radiation (X and Y). It is available as single sheets, laminated or incorporated into double glazed units. X-ray protection glass is used in medical or industrial radiology rooms.
Electrically Heated Glass
Electrically heated glass was first developed in World War II to prevent aircraft windshields from frosting over and obscuring visibility. Since then, this technology has been become almost universally used in aviation. It has even reached supermarket freezers, where glass doors must remain clear for customers to be able to see the merchandise. It is a laminated glass, incorporating almost invisible electrically-conductive wires. It comprises two or more sheets of glass interlaid with one or more films of polyvinyl butyral (PVB). This assembly combines comfort with safety, whilst preventing condensation. Electrically heated glass is suitable for any situation where there is high moisture content in the air and where the difference between the internal and external temperature may lead to condensation risk.
Production: In order to electrically heat glass, a microscopic Tin (II) Oxide coating is applied to a pane of ordinary float glass. This coating is perfectly transparent and conducts electricity. An electrical current is supplied by two busbars located on opposite sides of the glass. The electrical resistance of the Tin Oxide coating produces heat energy. This heat radiates from the glass in the form of infrared energy. The busbars are typically connected to a power control unit that regulates the flow of electricity and thus the temperature of the glass.
Electrochromic glass is an energy-saving component for buildings that can change color on command. It works by passing low-voltage electrical charges across a microscopically-thin coating on the glass surface, activating a electrochromic layer which changes color from clear to dark. The electric current can be activated manually or by sensors which react to light intensity. Glass darkening reduces solar transmission into the building. When there is little sunlight, the glass brightens, so that the need for the artificial light is minimized.
Liquid Crystal Glazing
Liquid crystal glazing is laminated glass, with a minimum of two clear or colored sheets of glass and a liquid crystal film, assembled between at least two plastic interlayers. In the OFF state, the liquid crystals are not aligned, which prevents vision, yet allows light to pass through the glass. When is it switched ON, the liquid crystals align, turning the glass transparent and allowing vision through the glass. The change of transparency takes place within milliseconds. Liquid crystal glazing is designed for internal applications, including partitions, display cases, bank screens.
Self-cleaning glass is an ordinary float glass with a special photocatalytic coating. It is made by chemically bonding and integrating a microscopically-thin surface layer to the exterior surface of clear glass. The integrated coating reacts to the sun?s ultraviolet rays to gradually and continuously break down organic dirt through what is called a photocatalytic effect. In other words photocatalytic means that the active integrated coating on the outside of the glass absorbs the sun?s ultraviolet rays. This causes a reaction on the surface which breaks down dirt and loosens it from the glass.
This type of glass also has hydrophilic properties, meaning that rain flows down the pane as a sheet, washing away the dirt instead of, as with normal glasses, leaving the dirt behind. As a result of these two effects, the special self-cleaning coating keeps the glass cleaner for a longer period than with normal glass in applications where it is exposed to the rain.
Sandblasted glass is produced by spraying sand at high velocities over the surface of the glass. This gives the glass a translucent surface, which is usually rougher than that obtained by etching. During sandblasting, only the areas that are to remain transparent are masked for protection. The depth and degree of the translucency of the sand-blasted finishing vary with the force and type of sand used.
Sand-blasted glass can be used in numerous interior design applications in both residential and commercial settings: doors, shower screens, partitions and interior screens, furniture, etc.
Bent glass is a normal glass, which is curved with a special process. It can be used for external sites, such as facades, shop fronts, panoramic lifts etc. and is also commonly used for internal sites in showcases, shower doors, refrigerator cabinets etc.
Production: Bent glass is produced in a horizontal mould by slowly heating the glass to approximately 600°C, at which the glass softens sufficiently and takes the shape of the mould. The glass is then slowly cooled to avoid any internal stress. The mould itself plays a very important role in bent glass manufacturing because it determines the quality and angle of the curve.
Fire-resistant glass can be classified in two categories:
- Fire-resistant glass – heat transmitting glass: contains flames and inflammable gas for a short period of time, but does not prevent the transmission of heat to the other side of the glazing.(example: wired glass, reinforced laminated glass).
- Fire-resistant glass – fire-insulating glass: contains flames and inflammable gas for a longer period of time and prevents not only the transmission of flames and smoke but also of heat to the other side of glazing.
Alarm glass is a special laminated glass designed and manufactured for security purposes.
The interlayer is embedded with a very thin wire and then “sandwiched” between two or more sheets of glass. The wire forms an electrical circuit which activates alarm when the glass is forced.
Anti-reflective glass is float glass with a specially-designed coating which reflects a very low % of light. It offers maximum transparency and optical clarity, allowing optimum viewing through the glass at all times.
The clarity of vision makes anti-reflective glass suitable for all applications where glass should be transparent.
- Exteriors: shop fronts and commercial frontages, glazing where vision is important, particularly at nighttime(panoramic restaurants, air traffic control towers, petrol station windows) etc.
- Interiors: high quality picture framing, display cabinets and interior display windows, dividing screens in cinema projection rooms, television studios, machine control rooms etc.