Coatings on Glass
Why are coatings applied to glass? What are a coatings? How do they work? How are they applied? These are all frequently asked questions about a growing segment of the architect’s tool kit. This article provides an overview for one of the many types of coatings available: thin, transparent films on glass.
Coatings on glass are a means of extending the usefulness of glass by adding an extra aesthetic dimension and enhancing its thermal performance. Uncoated glass is commonly available in eight basic tints and thicknesses from .085 inch to 1 inch. The largest share of the commercial market is ¼ inch (also called 6 mm). The need for more energy-efficient buildings has pushed this market into using insulating glass units and away from single glass lites in many geographical areas. Adding thin films to the inside of these units adds even better performance.
There are many types of coatings: bulk coatings such as frits and paints for spandrels, translucent lites and decorative panels; coated plastics that are applied to glass either by a fabricator or in the field, and some are even suspended in insulating glass units for improved thermal performance; vacuum and pyrolytically deposited coatings.
The term coating is used broadly and many of the processes are referred to as coating processes. The word film is also used broadly and refers to either the layers deposited by vacuum and pyrolytic processes or the coated and uncoated plastics applied to the glass surface or suspended within an insulating unit. While plastic films are occasionally confused with thin films, the difference is the thickness of the product applied on the glass. The plastic films are bulk materials. They may have a very thin film on one or both of their surfaces, and they can be handled like a delicate plastic wrap. The thin film, which is the topic of this article, is applied to the glass directly by the vacuum or pyrolytic processes.