There is an extremely low probability that Contra Vision Privacy Window Films will exacerbate existing imperfections in glass and cause it to break. We receive 1 reported case for every 250,000 square metres (2,500,000 square feet) of perforated window film sold.
The main risk is thermal stress caused by differential expansion between adjacent areas of the glass. This normally occurs because sunlight heats the central area of windows, but the edges are shaded. The most important factor is the type and quality of the glass. Tempered/toughened glass is unlikely to give any problems because it has very high edge strength and thicker glass is also better. The edge strength of glass can be compromised by small imperfections such as “inclusions” (foreign matter) and how it was cut and treated by the glazier. Other contributory factors include the level of external and internal shading.
Normal window films (non-perforated) are known to increase the risk of thermal stress because they absorb a higher level of solar energy than the glass on its own. The risk is likely to be reduced if a perforated window film is used. This is because the holes help to reduce the relative temperature change and consequent thermal expansion that would take place with the same graphic on a solid substrate. Avoiding dark colors (which absorb more heat) will also reduce the risk.
A thermal stress fracture is easy to spot. One end of the fracture will be in contact with the edge of the window, in a line of about 2-3cm (1 inch), which is a right angle to the edge of the glass. The crack can then deviate in any direction from there.