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Volume 7, Issue 1        January/February 2005

Ask the Doctor
by David A. Casey

Q. I often have problems filling one or more legs of a star break completely. Sometimes it is only the last 1/8 of an inch. I alternately apply pressure and vacuum, but often it does not work. Occasionally, a customer calls to inform me that the break has cracked out, and, inevitably, the crack has started from the unfilled leg.  My other problem with star breaks is with getting resin into legs that do not extend to the pit. Can you help?
A. The unfilled tip of the crack is usually the result of air being trapped and/or a very narrow spot in the crack. Your technique of alternately applying pressure and vacuum is correct. If you get a good vacuum before you inject the resin, you will rarely run into this problem. There are a great variety of bridges used in our industry and the strength of their vacuum dictates how long you need to leave it on before injecting the resin. It could vary from a few seconds to five minutes or more. Experiment with your own equipment and do not rush the process.

Also, while on the pressure cycle, press the glass at that point with your probe and hold it until the resin flows in.

To join the unconnected leg(s) to the pit: remove your pump and press down on the gap between the pit and the unconnected leg with your probe. This will crack the glass and open a path for the resin. If this fails, insert a #14 sewing machine needle in the pit at an angle toward the leg and tap it lightly to open a passage. A drill can also be used. 

Q. What are stress cracks and what causes them?
A. Stress cracks are usually, but not always, vertical and extend down to the edge of the windshield. There are no dings or chips associated with them. They are caused by problems with the vehicle’s frame, usually as a result of an accident. They can also be the result of a faulty windshield replacement.

There is no point in repairing them until the underlying cause has been eliminated. They will crack open again.

Walt Gorman is the owner and founder of A-1 Windshield Doctor in Seekonk, Mass. He has 17 years experience in windshield repair and runs a training school for technicians. E-mail your questions to

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