In the awe-inspiring world of glass, reflective glass occupies a significant position. Besides the basic functionality of sun control, it contributes to architectural aesthetics and even energy conservation. Reflective glass helps a building achieve a high standard of visual appeal besides reflecting a greater amount of heat than normal tinted float glass, making it less prone to thermal breakage.
Reflective glass is essentially ordinary float glass with a metallic coating that cuts off solar heat. This special metallic coating also provides a one-way mirror effect, preventing visibility from the outside and thus preserving privacy. Reflective glass is used primarily for structural façade glazing.
There are two different ways of manufacturing reflective glass - production pyrolitic process and vacuum (magnetron) process.
1. Production Pyrolitic (On-line):
In this process, semi-conducted metal oxides are directly applied to the glass during float glass production, while the glass is still hot, in the annealing lehr. These coatings are called hard coatings, and are relatively less harmful to the environment.
In summary, pyrolytic glass is a reflective glass that has had a coating applied to it during float glass manufacture. The coating is fused to the glass at 1200o C. The best feature of this product is its durability; it can be easily handled like a standard square of glass. It can also be easily cut, heat strengthened or toughened. Pyrolytic glass is sometimes referred to as “hard coat” reflective. Since it is processed online, it works out to be cost-effective.
2. Vacuum (Magnetron) Process (Off-line):
In this process, one or more coats of metal oxide are applied under a vacuum to finished glass. The coatings applied by this technique are soft and require protection from the external environment; they are therefore applied on the inner side of glass panes. Their low resistance makes them better off when used in a double glazing system. Cost-wise, this glass is relatively expensive.
Other offline coating techniques are as follows:
• Immersion process
• Chemical process
• Screened glazing
The manufacture of this type of glass involves the deposition of metal particles on the glass surface by a chain reaction in a vacuum vessel. It is often called a “soft coat” because the coating is more susceptible to damage than a hard coated glass when glazed in monolithic form. Where toughening of the product is required, the product must be first toughened and then vacuum coated.
Vacuum-coated glass is available in laminated form with the coating on the inside. Subject to certain exceptions, vacuum-coated products have better shading coefficient values than pyrolytic products.
Anti-reflective glass is float glass with a specially-designed coating which reflects a very low percentage of light. It offers maximum transparency and optical clarity, allowing an optimum view through the glass at all times. The clarity of vision makes anti-reflective glass suitable for all applications where transparency is required.
Application in Exteriors:
At shop fronts and commercial frontages, where vision is important, particularly at night time (panoramic restaurants, air traffic control towers, petrol station windows) etc.
Application in Interiors:
For high quality picture framing, display cabinets and interior display windows, for dividing screens in cinema projection rooms, television studios, machine control rooms etc.