Glass crack pattern

In this case, the building had both: edge damage and underspecified glass. Reflective blinds and a South exposure combined to create a high frequency of this type of breakage. You might have to look hard because the oyster could be buried in the primary seal on the 2 or 3 surface. Another clue would be the distribution of glass breakage in the building. It would be normal to find stress-like cracks on elevations with greater temperature swings.

But does the breakage also coincide with the use of reflective interior blinds, especially in a partially opened position? That would be indicative of a true stress crack, rather than a crack induced by edge damage. Also, look outside. Is there something that shades the glass partially? That could be a factor.

Want to learn more about nickel sulfide inclusions that can spontaneously shatter temper glass? See this photo album: Nickel Sulfide Inclusion: A tiny speck that destroys tempered glass Great resource from Viracon Viracon Technical Information: Thermal Stress Breakage Mark Meshulam,glass consultant, observing that glass is not broken Need a glass consultant to diagnose glass breakage or investigate a broken glass injury?

Coming soon to your area! No matter where you are, contact me, Mark Meshulam, the Chicago Window Expert to learn all about windows and glass! My email: Mark ChicagoWindowExpert. If you are in these areas and need help with your building, call right away and save costs. Pretty good post. I just found your site and wanted to say that I have really liked reading your posts.

I know the family that ownes Florida Crush Stone. Do you want me to help forward this site to people in related industries? Do you work with companies around the country? How small is too small?

I would be grateful for readers forwarding this site to other interested parties. Yes, we do work with companies around the country, despite the ChicagoWindowExpert name. In the consulting part of our business, there is no job too large or small. Thanks for writing! Thanks for the nice comment from my friend Victor Wei of Yuanda. Congratulations to Yuanda for those two wonders! I came across your website and found it very helpful.

I was curious if you had any photos of nickel-sulfide inclusions? Based on the tempered glass breakage photo on your website, it would appear that my living room window has a point of impact. The outside window pane is intact, according to the supplier. Hi Kim, According to my glass experts, a nickel sulfide inclusion should be visible to the naked eye. Attached please find an interesting photo I recently came across.

Hi, Kim, I am working in a window glass production plant. Recently I am getting more complaint from my customers regarding temperness. But I found very good cutting in size before packing.

The pattern you see on the background of this page scroll all the way down is a clasic breakage pattern of tempered glass. I recently learned that it is possible for a lite of glass to be incompletely tempered, i. Although I have never seen it, this condition could result in a hybrid breakage pattern that transitioned from the tempered cubes to larger shards. Has anyone out there ever seen such a thing? Since tempering occurs when glass is heated then rapidly cooled, I would imagine an uneven temper could result from uneven heating or cooling.

I have experienced the incomplete tempering process. It is a laminated glass, the breakage happened at surface no. The breakage pattern is as shown in the background, just like a tempered. Hi Mark. I stumbled on your article while researching a problem I have. Perhaps you can help me? I recently broke a peice of safety glass in one of my homes french doors.

There are 15 seperate glass panels and they are double paned. The glass that shattered remained in place entirely — just completely cracked. I have no idea how to carefully get the broken piece out though without possibly breaking the pane behind it too. Should I just carefully tap on it with something like a screwdriver until it punctures it?

Mark, I cleaned the outsides of the exterior windows on a newly constructed large downtown building. The windows have the new external aluminum window louvers attached above in strategic locations on the east south and west sides of the building. This is a very time intensive job and after a month we are finally wrapping this up. This just happened over the weekend. What are your thought on this? There can be many reasons for this type of breakage.

First, there will always be a few lites that seem to break spontaneously during the first few years of building operation — usually this means that there was a hidden weakness, such as edge damage or an inclusion, that finally got around to breaking. Temperature fluctuations help bring out hidden defects. If it is not edge damage or an inclusion, then the glass may not be designed for the conditions.

In other words, if the louvers or other projections cause a pattern of triangular shading on the glass, if the glass is annealed only, it may break. If they want to blame you for the crack, get pictures and ask them to show you the point of impact.

If glass is broken by impact, there will be a very noticeable point from which many cracks emanate. Unfortunately too many manufacturers make their products difficult or impossible to reglaze. Shame on you, window manufacturers who do this. You are screwing the public! The glass will be held in by two things: stops and sealant. If it is a wood door, the stops will be little strips of wood nailed just to the interior side of the glass to hold it in place, although with some of the high strength sealants out there, it is not really necessary, except for appearance.

Gently and carefully remove the stop by sliding a sharp razor knife along the seam between the stop and the frame and also between glass and stop to separate the stop from the frame. You should now see the glass edge. Measure the actual glass size. Go order a piece of replacement insulated glass.

When it arrives, remove the old glass by any means possible: cutting along the glass where it is adhered to the frame on the exterior, cutting away any sealant around the glass edges visible from the interior, prying and prying every witcha-way.

If the glass is stubborn, and it is tempered, nick away at the face of the glass with the claw end of a hammer until the glass breaks, then peel and clean it away. I am not a fan of removing the broken lite and leaving the intact lite. It will look strange and who needs that?

The owner said it was out fault , Now he wants new mirrors. He is a good customer. In front of these mirrors on the floor is a weight rack where they are picked up and put down. I told them that the floor was bouncing up and down. I think I am right. I have recently visited your website chicagowindowexpert. Can this pattern also be a result of thermal or temperature related stress? If not, can you tell me what kind of object or impact would cause such a pattern?

Thanks a lot! Full width of lite Closeup of center. Hi TJ, It looks like the glass is receiving some loading from above. Remove the interior glass stop at the top of the glass lite and see if the frame is touching the top of the glass this would be bad. Then remove the bottom glazing stops and see if the setting blocks are at quarterpoints. I am going to guess that the setting blocks are at the transition between the cracked area and the middle bottom crescent.

I finally had a chance to take a look at the glass weather is finally warm enough! The frame was touching exactly where you thought it was, I suppose it is due to the settling of the frame.

The settling blocks were at quarterpoints and between the cracked area and the middle-bottom crescent as you said!

Microscopic imperfections buried within the pane are behind the spate of exploding glass balconies on downtown condo towers, an engineer says.

Brook recently discovered nickel sulfide crystals in two shattered panes. These crystals grow over time, which stresses the glass. If the imperfection is in the right place, the pressure builds until the pane explodes. But the engineering firm was lucky. It had been testing intact panels from the north tower of the Murano building as the developer took them down. One night, a pane resting against a wall in the testing facility exploded. They found their specific glass bit.

Brook first suspected the faulty glass was from a bad batch. It was actually several contaminated batches from manufacturing facilities in the United States that ended up in Toronto. When the weather got extremely cold this past winter, a crack started from the oyster and ran down the window about 18 inches. The house was just a few months old, and the Builder is refusing to replace it. If you have any pictures, that would be very helpful. An oyster is a clamshell-shaped chip in the surface of the glass, usually emanating from an edge.

It is the result of damage to the glass edge, such as might occur if the glass were pried in place with a metal prybar during installation. Glass edges are sensitive and brittle. They should never be allowed to contact metal. Wood is used frequently for standing a lite of glass onto prior to installation. Once installed, the glass should be sitting on hard rubber neporene is often used setting blocks at the bottom quarter points.

If your glass was already installed into the window when it arrived to your jobsite, the edge damage probably occurred at the factory. If they refuse, let me know. Maybe I will be able to persuade them to do the right thing. The photo below is at the bottom of the glass just next to the setting block. Discover an entire network of professionals to assist with any of your home service needs at GetNeighborly.

Skip to main content. Your health and safety are our highest priority during this time. Click here for our precautionary measures. Still open to serve you. I'm surprised this question has remained unanswered for so long. And yes, I agree that the web page provided gives a completely unsatisfactory answer. The solution to the problem is fairly complex, so we need to break it down into a number of issues to look at.

The cracks radiating from the center of impact are easy to explain. Flat glass laid on the ground and hit with a hammer also produces these radial cracks from the centre of impact. This is caused by the rigidly flat surface trying to form a cone shape. You can only cut triangles around a point in a flat surface, and allow those triangles to spread apart at the apex to form a cone. Flat glass laid on the ground tends to have few lateral or circular cracks, depending on irregularities of the ground.

If you hold a piece of flat glass horizontally and hit it with a hammer then the cracks and broken pieces tend to be more random, but since you are holding a point you often get radial cracks emanating from that point.

It is much safer to hold flat glass vertically when hitting it with a hammer as the radiating cracks emanate from the impact point. The speed of sound within a material and its elasticity definitely has an effect on the formation of the lateral or circular cracks. In so far as the distance between them from the centre of impact, is produced by a "deformation wave" spreading out.

Formation of lateral cracks are caused by a lever like action that is easiliest explained by taking a ruler and holding it down so that it overhangs a desk. Push down on the unsupported end with your other hand, and you will find that the freely moving length of the overhang acts like a lever to break the ruler near the rigidly held end.

When an object stops it does not just stop instantly, it has to "decelerate" in the same way that an object has to accelerate to get up to speed. Even a rubber ball thrown against a brick wall spends a small amount of time deforming and storing its kinetic energy of motion in its elastic bonds, which in turn is release as the ball "springs" back away from the wall. The Initial Fracture Surface provides critical information to describe glass breakage, including the mode of failure mechanical or thermal and the tensile stress at glass breakage.

The direction of crack propagation proceeds from the concave to the convex side of these lines. Primary Wallner lines indicate discontinuities before fracture occurs. Secondary Wallner lines indicate the crack front as it approaches terminal velocity. Tertiary Wallner lines form due to an external shock or pulsed energy, triggering the onset of continuing crack growth.

Crack patterns provide significant clues to describe glass breakage when coupled with information about the Initial Fracture Surface. In AN and chemically-tempered glass, cracks form as single or branching lines. In HS glass, cracks form as multiple single and joining branching lines. In FT glass, cracks form across all surfaces, creating a multitude of small fragments. In all flat glass, low-stress cracks, due to mechanical stress e.

High-stress mechanical cracks have similar orientations with branching cracks that break away from the initial crack within two inches of the initial fracture surface. On the other hand, low-stress thermal cracks are typically oriented perpendicular to glass edges and surfaces; high thermal stress cracks have a similar orientation with branching cracks that branch from the initial crack within two inches of the initial fracture surface Figure 4.

High-stress edge and surface cracks form as many radiating lines with circumferential rings. Special considerations for glass breakage relate to thermal stresses and spontaneous breakage. When AN glass heats up under direct or reflected solar radiation, glass central regions expand relative to colder edges.

Thermally-induced hoop stresses can create tensile stress concentrations at critical edge flaws. Spontaneous breakage can occur due to surface damage propagating through RCSS surfaces under cyclic loading or due to Nickel Sulfide NiS stone inclusion or other batch impurities in the manufactured glass material.

NiS stone inclusions undergo an expansive phase change in their crystalline structure that, due to the relatively quick quenching of FT glass, has the potential to occur sometime after fabrication. HS glass quenching occurs slowly enough to allow NiS stone phase change and, like AN, does not suffer from spontaneous fracture due to NiS stone inclusions. The expansion in a NiS particle can cause a fracture in the body, which, when propagated to FT glass surfaces, suddenly releases RCSS throughout the glass body, causing breakage.

Not all cat-eye fracture patterns are due to NiS stone inclusions. Laboratory analysis such as Scanning Electron Microscopy SEM can positively identify impurities in the glass body to confirm the cause of spontaneous breakage. The following projects provide examples where the crack pattern and initial fracture surface were vital in determining the glass breakage story. This project includes a multi-layered structural laminated glass cantilever tread staircase in a private residence Figure 6.

The tread specification considered conservative static and dynamic stair loads, plus post-breakage capacity for safety, using AN glass laminated with a stiff structural interlayer material. Installation details included set-screw level adjustment with a maximum setting torque specification into padded brackets, with each tread independently installed and test-loaded.