Architects’ desire for transparency coupled with new code requirements is pushing fabricators to meet the demand for well aligned, exposed edges with laminated glass.

When it comes to achieving good quality edge work, fabricators often are caught between the aesthetic demands of architects and ASTM standard guidelines. This has become more of an issue in recent years since the 2015 International Building Code required that fully tempered laminated or heat-strengthened laminated glass be used in railings with a 30-inch drop.

An interlayer sandwiched by two glass lites must be used in such applications to prevent the small pieces of shattered tempered glass from falling on someone walking below the glass. Keeping the glass in the opening also can prevent someone behind the railing from falling.

Aligning the edges in laminated glass is not always easy, and it’s a topic of conversation among fabricators as architects continue to desire minimal hardware in railings and other glass applications to maintain transparency and views.

Edges Exposed

Jim Smith, director of Invisiwall engineered glass systems at Consolidated Glass Holdings (CGH) based in Pedricktown, N.J., says that his company is seeing more applications with exposed edges, including handrails and canopies.

“Edge conditions on laminated glass are critical to getting the aesthetics [architects] want … We’re seeing a lot of architects pushing the envelope for superior edge conditions that only a few fabricators can adhere to,” he says.

Brian Dawley, senior technical services representative for Viracon in Owatonna, Minn., says his company tries to hold tolerances tight so the glass doesn’t slip too much during the lamination process. He explains that his company keeps tolerances tighter than the ASTM C1048 standard requires.

“Edges can still be within tolerance and visually appear slightly off,” he says, adding that if the edges are within tolerance they are considered good. “If deemed unacceptable they would purchase a new lite and hopefully get quality more to their liking.”

Achieving Alignment

Paul Mouton, senior sales development at Midwest Glass Fabricators (MWGF) in Highland Township, Mich., says that while fabricators can achieve tight tolerances, it’s important to educate architects and glaziers on what’s reasonable.

“If an architect wants to hold the tolerance to 1/64th of an inch, much like monolithic glass, that type of tolerance is not achievable unless using high precision equipment which is expensive,” he explains. “A lot of times they’re putting that in the spec because it was something handed to them in their drawings. It’s not terribly reasonable.”

Smith explains that while CGH’s techniques are proprietary, great detail goes into the preparation of the product before it goes through temperature changes in the autoclave to promote polymer flow.

He also points out that if there are discrepancies in the size of the two lites of glass used, it will cause misalignment no matter what a fabricator does.

“The pre-oven process needs to create good alignment and stability before the product is put into the oven,” says Smith. “… There also needs to be special attention paid to trimming and post production. This is often done by hand.”

Ultimately, the best practices involved in achieving aligned laminated edges depend upon the lamination process used and the type of interlayer. There is no prescriptive method across the board.

To read the full article, which originally appeared in the January 2020 issue of USGlass magazine, click here.

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4 Comments

  1. The article is well overdue, however the ability to fine quality edgework for laminanted glass is a choice made by the individual processor. I am not sure we agree with any of the comments made in the article as we have been doing zero tolerance edgework for over twenty years on laminated glass. Check our Pulp Studio’s PRECISION EDGE. Edgework so perfect it finally got it’s own brand name.

  2. I have been struggling with current laminated glass in regards to exposed edge guardrail glass.
    Just getting the sizes correct and holes in correct locations is just the start.
    Then getting the supplier to stand behind their product is almost like squeezing blood from a turnip especially when they site allowable tolerances ..

    1. Mitch,

      Not sure where you are located, but if you post a general region I will let you know if there are any good fabricators in your area I have utilized with good results. Pulp is out West and they are great (used them for almost 20 years). McGrory is on the East Coast and also great (also used them for almost 20 years). Ive also had good results with Cardinal on larger non decorative laminated jobs and I think they have locations in the mid west.

      Thanks,
      Skip

  3. If you have a job that requires tempered lami with exposed edges and you are dealing with a fabricator that will use ASTM standards as their guidelines – that should be red flag #1. I would never give a company like that any of my orders for these products because ASTM allows far too much tolerance leeway especially in laminated glass doors. ASTM allows for more slippage than the clearances glass doors call for so theoretically you could procure a glass door thats meets ASTM yet won’t even fit into the door opening. All of the orders I place for those products are sent to a company that focuses on high end, high quality, decorative glass because they don’t need to be told that your order requires better than ASTM standards because they hold themselves to those higher standards every day as common practice. This can help you avoid many issues including drawn out litigation after the job is done. The same standards can be applied for the use of museum quality glass. In my career Ive found that the decorative fabricators that have been around for decades like McGrory Glass will handle every order with that kind of care. If I want Porsche quality and performance I do not go to the Ford dealer.

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