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September  2004

Fenestration Focus

“Easy to clean”
Incorporating this Glass into Window Operations
by Julio Diaz and Sal DiGregorio

Any homeowner who has spent a day washing exterior windows can appreciate the innovation of easy-to-clean glass (which some manufacturers refer to as self-cleaning). For window manufacturers, however, making this transition does not come without its own set of concerns. Fortunately, strategic material choices make alternating between conventional window glass and easy-to-clean glass on the production line transparent to the window manufacturing process.

The Secret is in the Surface
The key to easy-to-clean performance lies in a special finishing treatment of titanium dioxide (TiO2) applied at the final stage of the glass manufacturing process.

Under normal circumstances, the easy-to-clean action of this treated glass minimizes the need for cleaning maintenance. Under exceptionally dirty conditions, however, some simple cleaning efforts might be needed.
But before consumers can enjoy the benefits of easy-to-clean properties, manufacturers must resolve certain compatibility issues with the glazing processes used when assembling window units made with easy-to-clean glass.

Product Compatibility
While the physical properties of the easy-to-clean glass surface perform admirably in their ultimate application environment, they require careful material considerations in the manufacturing and installation process.

For example, many traditional wet-glazing systems are not directly compatible with the TiO2 modified surface of easy-to-clean glass. Oils in some glazing compounds can affect the bond. Because some traditional glazing materials do not cure to be 100-percent solid, solvent emissions can create residues that damage the TiO2 treatment. This limits the effectiveness of the easy-to-clean properties in those damaged areas thus producing noticeable blemishes.

Due to the TiO2 treatment, traditional wet-glazing materials that work with conventional glass lites can experience adhesive failures when used with easy-to-clean glass. But even where reformulations of traditional wet-glazing compounds can be adapted, switching back and forth between glazing compounds for easy-to-clean and conventional glass can disrupt production-scheduling flexibility.

For these reasons, it is important to consider glazing materials that are proven to be compatible with the TiO2 surface of easy-to-clean glass as well as with most other coating materials (i.e. laminated, tempered or scratch-resistant glass) or frame materials (i.e. composite or painted frames) used in window production. For instance, products such as immediate-strength polyurethane reactive glazing compounds use thermosetting properties to cross-link the various chemicals and reduce the chance of troublesome compounds leaching out.

Simplified Production
In addition to satisfying the chemical compatibility and performance issues of easy-to-clean glass, manufacturers should carefully choose glazing materials that can speed up and simplify the production of any type of window. This is especially important when using different sizes and types of glass on the same production line.
glazing materials with quick-setting properties for a variety of window sizes help to speed up production. Certain immediate-strength polyurethane thermal-reactive glazing materials are applied at elevated temperatures and begin to harden and adhere upon contact with the room-temperature window frame. 

Satisfying the Consumer
The challenge of capitalizing on increased consumer reaction to easy-to-clean glass includes meeting the physical compatibility needs of this special glass surface without complicating production scheduling or quality control issues in manufacturing easy-to-clean windows. Look for versatile and compatible glazing materials to help satisfy both of these needs.

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