“Layton Consulting Fenestration Nerds”: Fracture Facts By Tiger Lu.
If you’re an avid reader of our blogs, you’ll notice I am new to the Layton Consulting team! My name is Tiger Lu, and I recently earned dual bachelor’s degrees—one in Natural Sciences from Pepperdine University and another in Mechanical Engineering from Washington University in St. Louis. During my time at Pepperdine, I joined a small research group that focused on forensic fractography (shoutout to my partners Camdyn Munger and Michael Yeung)! Our supervising professor, Mary Holden, was mentored by George Quinn, a pioneer of the glass fractography industry. Over three years, our research evolved from analyzing simple cantilever breaks to simulating skull fractures for the FBI, but our goals remained the same. To learn how to take any broken glass, put it back together, and determine why and how it broke. There’s decades worth of knowledge to be studied here, but let’s start with some basics.
Glass fractography is an exercise in patience. Broken glass may seem like a mess of identical shards, but each piece holds clues. Unlike ductile materials like steel, which bend under stress, glass is brittle, glass fractures without warning. This trait makes it surprisingly traceable: since glass doesn’t deform, the fragments precisely fit together. Like a 3D puzzle, the challenge lies in finding perfect matches between uniquely shaped pieces of identical material. Early on, it could take me hours just to find a single match, and up to ten hours to fully reconstruct a glass dish. The first pair always took the longest. And yes, it was frustrating!
Reassembling the glass allows you to trace fracture markings back to the “origin”—a distinct point on the fracture surface that shows where the break started. You might say, “Well, Tiger, why would I have to put the entire piece back together to find the origin? If I knew where the glass was hit, I’d know where the break began!” While that may be true sometimes, glass fractures don’t always start at the point of impact; they might start at a different location where there was higher tensile stress. The fracture might have occurred due to pressure, not impact, and there might even be two origins. The only way to know for sure is to put the entire glass back together and find the origin(s). Because the actual fracture origin will be very small, you’ll be looking for the origin through three subsequent markings that always immediately follow it: the mirror region, the mist, and the hackle. Most importantly, the radius of the mirror region can be used to calculate the stress at the point of failure.
Ultimately, the fracture origin is the most important feature to understand in glass fractography. In a simple rectangular pane, origins located at the edge may indicate a hinge fracture or a break due to thermal expansion. “Butterfly wing” patterns often point to nickel sulfide inclusions, which are typically found in tempered glass. In household glassware, origins that begin as slow-moving rings usually suggest thermal shock. Another notable feature is the Hertzian cone—a distinct marking caused by a high-speed projectile impact. There’s much more to explore in this field, but I hope this gives you a solid starting point. And while it might be tempting to try this at home by breaking your own glassware and reconstructing it—please don’t! Leave the puzzle-solving to the lab.