Tracy Rogers, technical director of Edgetech IG in Cambridge, Ohio, addressed an oft-overlooked area of the building process—post-construction cleanup—June 17 during Glass Performance Days in Tampere, Finland.
Rogers talked about planning during pre-construction by protecting exterior fenestration and glazing surfaces with applied coatings.

“The construction process results in a variety of materials being inadvertently splashed, splattered and sprayed on the exterior of fenestration and glazing systems,” Rogers said. These include paints, stains, concrete, stucco, weld splatter dirt and other debris.

Rogers said a primary issue in the glazing industry is the use of razor scrapers on glass and frames, particularly tempered glass. He showed an article about a new building at the University of Saskatchewan, Canada, that needed three-quarters of its windows replaced as a consequence of cleaning. The scratched glass led to an incremental cost of $200,000.

One of the reasons scratching occurs is because the surface of float glass products is replete with minor surface variations and defects. Some materials such as concrete can interact with the glass and chemically bond to the surface. A visible erosion mark can be created when the concrete is scraped from the glass.

“A film barrier between the glass and any external debris that is pre-applied and easily removed during post-construction cleanup is the obvious solution,” Rogers said.

Three film-barrier systems are available in the market. Pre-applied plastic films adhere to the surface with a temporary adhesive, static cling or both. They are typically removed by peeling the film from the unit. However, the films have the potential to lose adhesion.

Site-applied liquid coatings can be applied by roller, brush or spray before major exterior construction and then peeled off.

Grafted polymeric coatings are water-based and applied to the exterior of the fenestration or glazing assembly before shipment to the job site. The polymer cross-links into a solid protective film during the drying process. The coating bonds to the surfaces once cured.

It’s removed though a water-based “converter” that breaks the cross-linked bonds of the grafted polymer coating. It’s then rinsed off with water along with attached debris. The converted coating is bio-degradable.

Laser technology
Representatives from two companies demonstrated CO2 laser radiation and near-infrared radiation laser cutting June 18.

Michael Degel of Jenoptik, Germany, said the company has developed the cutting of thicker glasses using solid state laser, which offers a clean cut without the need of breaking. The CO2 lasers can be implemented into existing production processes.

The thermal laser separation method includes an initial crack, heating by laser, heat conduction, cooling by a water-air aerosol and then separation. Tests have shown no defects on the cutting edge and an increase in bending strength.

Micahel Haase of H2B Photonics, Germany, followed by showing NIR radiation, which used multiple laser beam absorption. Unlike CO2 laser radiation, NIR laser radiation is absorbed through the entire glass body and does not require additional cooling mediums.

MLBA technology allows the separation of stacked glass layers in one processing step and eliminates the breaking process. Selective cutting of single glass sheets in a multilayer stack also is possible.

Alexander Zhimalov of Saratov Glass Institute, Russia, ended the sessions on laser technology by presenting the influence of glass edge processing on its strength and thermal stability.

The test results showed the strength of the glass edge with laser cutting is about five times greater than the strength of the edge with a mechanical cut, and two to three times greater than the strength of the breakage edge.

The thermal stability of the glass edge with laser cutting is about 40 percent greater than the thermal stability of the glass edge with a mechanical cut.

—By Matt Slovick, editor in chief, Glass Magazine

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