Some folks are just too independent to have a partner. We like to call all the shots and do not answer to nobody. In fact most self employed business owners are those types, including myself. We will take a silent partner any day though, one that drums up business but says nothing and does not even take a pay check. The silent partner of your auto glass business is the Frit.
Thermal stress occurs when there is temperature variance in different parts of the glass. If the stress caused by the temperature difference is greater than the strength of the glass, thermal stress glass breakage will result. A glass fracture can be identified as thermal stress breakage if the start of the crack is 90 degrees to both the edge and face of the glass. You will call this one a stress crack as it will have no impact point but surface pits in the Frit area will cause an edge crack also from thermal stress and this will be the pinhead size surface chip that those ethical auto glass shops that tell consumer the truth as to repairable damage see when they repair an edge crack. I say ethic because those that repair per the ROLAGS standard know that over 50% of edge cracks have an impact the size of pin head or even as small as a grain of sand instead of one the common stone-break types of breaks. This is also much easier to repair than when the impact is a star or combination break.
