Glass Expert Analyzes WIndow Damage

Glass failure analysis expert analyzes scratched windows on new construction. There have been numerous occasions where a glass expert has been brought in the determine the cause of window scratching. This is often on new construction that has a stucco exterior. Post construction window claening is critical because of adhered construction materials. Removal of these materials is difficult because of their adhesion. Therefore, cleaning crews should not use blades to remove debris. In many cases abrasive debris such as stucco or cement can be captured by the blade and scratch the glass as the blade is being drawn across the surface. Abrasives can also be captured by dry cloths and pads and can also cause window scratching. The photographs above show the resulting window scratches. Upper left is a sample of cloth related window scratching, and upper right is a sample of metal blade related window scratches. These are window cleaning related and are not manufacturing defects. Only experienced window cleaners should be assigned to clean windows on new construction.

GLass Expert Discusses WIndow Failures and Window Evaluations

Glass experts at Read Consulting provide services as window experts. Read Consulting offers a wide spectrum of window testing and evaluation. Included are glass failure analysis, evaluation of window damage and window scratching, window performance (light transmission testing of low-E windows), problems with laminated glass, temper level of tempered and heat strengthened glass, nickel sulfide induced failures of tempered glass and window distortion. These services are a natural outgrowth of continuous involvement with glass, glass properties and useable items made from glass.

WIndow Defect Analysis

Glass failure analysis expert witness has analyzed numerous cases of window damage. Often a metal blade is used by the window cleaners. In many cases the window damage is found on new construction. GANA has specific window cleaniong instructions that forbid the use of metal blades. The concern is that the blades pick up abrasive particles that get between the blade and the window glass and cause glass scratching when the blade is moved across its surface. In the case of scratched tempered glass, there is a consern that glass particles have attached themselves to the window surface during the tempering process. Later cleaning will dislodge these particles and they will cause scratching. The california failure analysis expert has examined unscratched clean windows that have streaks that were shown to be adhered glass particles. This observation proves two things:

1. Cleaning tempered windows with adhered particles can be done without scratching. Use of a blade during cleaning of tempered glass will cause scratching and the abrasive is not necessarily adhered glass. It can also be dirt or abrasive materials such as concrete or stucco.

2. Microscopic examination can be used to determine if there are glass particles stuck to the surface of tempered glass.

Above are two microphotographs of a tempered glass surface found to have adhered glass. Upper left is 25X magnification and upper right is a 200X magnification. This window was cleaned before the pattern of adhered glass was discovered. Tempered glass window cleaning defects can be avoided even when there are adhered glass particles. On ther other hand, it is extremely risky to use metal blades for window cleaning if window scratches are a problem.

GLass Expert Discusses Nickel Sulfide Spontaneous Failures

Glass failure analysis expert witness demonstrates that in the case of the spontaneous failure of tempered glass, the tempered glass failure is caused by the NiS particle. The failed glass door was taken apart to reveal the NiS particle. At this point the Wallner lines surrounding the NiS particle were located. The Wallner lines domonstrate that the NiS particle is in the center of the failure origin, and must be the cause of failure. The upper left photograph is a 20X photomicrograph of the NiS particle and its surroundings taken using Nomarski optics. Upper right is the same photomicrograph upon which arrows have been placed to show the crack travel directions as indicated by the Wallner lines. One can see that the NiS particle is at the center of the origin, and is the cause of the failure.

Glass Expert Performs Failure Analysis of Drinking Glass

In order to simulate potential cracking of a heavy bottom drinking glass still hot from a commercial dishwasher, a glass was immersed in 140°F water till stabile. The glass was removed and ice water was then poured into the glass. A glass failure analysis expert witness then performed a failure analysis on the resulting cracked drinking glass. The drinking glass tested is not new; therefore, there is random handling damage present both inside and outside the tumbler. The upper left photo shows the overall cracking resulting from thermal shock. To the right is a photograph of the cracked bottom of the glass. The location of the crack origin is indicated. The crack started in the center of the bottom on the inside surface. When the ice water hit the hot interior bottom, it put the interior surface in tension, and this started the glass cracking. Upper right is a 25X photomicrograph of the crack origin. The failure began at a point where there is a small bruise. It is important to see that there is no major handling damage at this origin. This is because the failure was driven by thermal stresses not mechanical stresses. In addition, the initial part of the crack at the origin is not straight. The direction of the stresses are changing even when the crack is initiating.