Expert Advice

Industry ‘Old Guard’ offers technical insights on iridescence, distortion and more during Fall Conference

Several of the glass industry’s foremost technical experts gathered at the National Glass Association Fall Conference to discuss top fabrication issues and challenges. Longtime technical leaders and members of the glass industry “old guard,” Chris Barry, Stan Joehlin and Bill Lingnell tackled technical insights on everything from iridescence to optical distortion to glass strength during the panel discussion, Solutions to Fabrication Challenges. Some takeaways from the experts:

Determining the source of distortion or failure of a glass unit requires close observation of a range of factors, Barry said. “Glass talks to us all the time. … Sometimes it’s shouting at us. It’s up to us to listen.” 

Barry also discussed edge treatment of glass—the grinding and polishing of glass with exposed edges, often done for handling and aesthetic purposes. “When you’re edge treating the glass, you’re not making glass stronger. You’re actually taking a nice smooth piece of glass and putting lots of little cuts into it. … At [the] end of the day, you have a nice piece of glass that’s easy to handle. But you’re not making the glass stronger,” he said.

Chris Barry-45 years in glass, including as former director of technical services, architectural glass, Pilkington, part of the NSG Group.

Visual mockups are essential to ensuring the expectations of all project team players—from the architect to the owner to the glazing contractor—are in alignment, said Lingnell. The mockups are particularly important when considering the optical distortion that can appear when using heat-treated glass products, he said. 

“Distortion is something we deal with. We can’t take it away. But, we can look at the glass beforehand by doing a real mockup,” he said. “As fabricators and consultants, glazing contractors, we can look at the glass with the architects, general contractors, owners. We can review the [specifications] and have a visual mockup to give a benchmark. We want to encourage folks to get out and look at the glass and understand it better, in mockup, rather than sometime down the road.”

Bill Lingnell-55+ years in glass, including leadership positions at a glass manufacturing, a wall systems company and a building envelope contractor

“In the last few years, I have been getting quite a few more calls on iridescence,” Joehlin said. The phenomenon occurs when stress differences in tempered glass become visible in certain lighting conditions, particularly when the light is polarized. “This is what gets you into trouble—it only shows up depending on the lighting conditions,” he said. 

To better control for iridescence, fabricators can look to several areas of their heat treatment processes that might be creating varying levels of stress in adjacent areas of the glass. Some causes include “misaligned nozzles, blocked nozzles or debris stuck in the fans. … Look at the age of the rings on the quench roll. If there is thermal conductivity there, that is a problem that causes iridescence.”  

Stan Joehlin-55 years in glass, including as vice president of operations and customer service, Glasstech