Window Defect Analysis Capabilities

Reflected Zebra Board Image that Shows
Window Roller Distortion Created
During The Thermal Temper Process

Window Scratches Caused by Poor
Cleaning Procedures

The window experts at Read Consulting are often asked to evaluate windows for defects. Many of these are Low-E windows that are also tempered. Two typical defects found are scratches and roller distortion.
Often the scratches are created during post construction cleaning. Roller distortion is formed when the float glass windows are thermally tempered.
Window Scratching: This is evaluated per ASTM C 1036 and is graded by the visibility of the scratches under controlled light conditions. Typical cleaning scratches are demonstrated in the above photo.

Window Roller Distortion (Tempered Glass Roller Distortion): This is evaluated per ASTM C 1048. Distortion in reflection using s standard "zebra board" (i.e. a standard striped pattern).  The photo above shows a sample of roller distortion found on a coated window. This test was done by reflecting the zebra board off the window outer surface. This test was performed on both window exterior surfaces. Often the amount of distortion allowed is defined by the construction contract. 

Glass Experts Examine Hotel Window Defect

 The glass experts at Read Consulting performed a window defect analysis on defective windows at a hotel. The windows began to appear dirty, and no amount of cleaning could remove the "dirt". When initially installed, the insulated glass (I.G.) windows appeared normal. However, over time they began to appear perpetually dirty. Using a microscope to look through the glass from surface 1, it appeared that surface #2 was heavily scratched. The window was disassembled and surface #2 was examined directly with a microscope. The defect was found to be in the Low-E coating on surface #2. This is a manufacturing defect and not the fault of the building owners. Product liability rests solely with the manufacturer.

Glass Expert Performs Failure Analy on Low E Windows

California failure analysis lab was asked to determine why windows in an expensive hilltop home failed. The windows in question were Lo- E windows that were tinted to absorb infra-red light. At this location two south facing, side-by-side windows cracked. The window expert at Read Consulting was asked to perform a glass failure analysis to determine the root cause of the failure. For this failure analysis the site of the origin was cut from the window and  the failure origin was examined using a low power optical microscope. Both windows failed in an identical manner. Thermal expansion of the center of the Low-E window put the ground glass window edges in tension.A damage site from either the window sizing or window seaming processes was activated by the thermally generated stresses and cracked these windows. Please refer to the photographs above.    

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.