Can You See It? Glass Damage That Is Hard To See And How To Repair It
Usually, when a customer comes into a glass repair shop to have the damages to their windows fixed, you can see why the customer is upset. The damage is visible, threatening to shatter, and/or is too dangerous to leave in place and drive around. Yet, there will be customers who come to the shop asking for damages to be fixed, and these damages are not so easily visible. When it is hard for a glass repair technician to see what you are talking about, it helps to find a way to A) reveal the damage, and B) ask for suggestions on how to fix it.
The Reflection Test
Hairline cracks in a windshield are really difficult to see. Usually a driver only notices them after something has hit the windshield, witnesses the sound and sight of the glass cracking, and then the glass rebounds into position leaving no traceable lines. You can show this damage to the repair technician by literally shining a light in the dark. Throw a dark tarp over the windshield. Then use a flashlight to shine through the area you believe has a crack. If there really is a crack, the newly-beveled inner surfaces of the cracked glass will reflect light that is incongruent with the rest of the windshield's surface.
The Drip Test
If the invisible crack tends to leak moisture when it rains, you can use the drip test. This requires pouring a lot of water over the area while holding or taping a dry rag to the damaged area. If successful, the water will seep through and wet the rag. Then you can show that to the repair technician.
Fixing Nearly Invisible Cracks
These types of cracks are hard enough to find and harder to make "visible" to the technician. When it comes to repairing them, there are only a couple of options. One, the technician can use heat to reunite both sides of the crack. This is a highly technical process that has to be done very carefully in a controlled temperature setting. Afterward, the windshield has to cool down slowly, so it cannot be exposed to extreme cold or the glass crack will not fuse properly.
The second option is to use a liquid glass filler that will slip in between the edges of the cracks and quickly harden like glue. It is slippery, like a lubricant, so that it can get into the nearly impossible to see crack and stay there until it dries. When it dries, you still will not see the crack, but you know it is fixed and will not get bigger or cause more extreme damage to your windshield.