by Bob Beranek
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Is an auto glass part still “safe” if it’s scratched? Well, it depends on the severity of the damage. A glazing professional will tell you if a glass scratch can be felt with one’s fingernail, the scratch is considered severe. If not, then it’s considered superficial and you can remove it on any glass part with “elbow grease” and some cerium oxide.

Severe damage indicates the removal of the scratch by whatever means, but will cause the glass to weaken, become distorted and be rendered unsafe. When an auto glass part is severely scratched the glass should be discarded. Auto glass parts are considered safe only when they’re not fractured. As soon as an auto glass part is broken it can’t do its job of supporting, protecting and providing clarity of site for the driver.

If you think about it, it makes sense. How is glass cut to size? The simple procedure is to “score” the glass and then break the score. What’s a score? It’s a controlled severe scratch created by a tool that breaches the harder surface of the glass by creating a fissure.

When pressure is applied to that fissure or score, the glass breaks controllably along the scratch that was created. A severe scratch is the first step in broken glass, you just don’t have any control over it.

Can auto glass be installed safely when there is a scratch present? If superficial, yes if it’s removed or accepted by the customer. If severe, no, just throw it away or return it.

Every repairable break is unique, and some repair professionals say a break or chip is like a snowflake. However, windshield breaks share certain characteristics that allow us to put them in generalized categories. These categories are bullseye, half-moon, star, crack and combination. The National Windshield Repair Association (NWRA) developed a standard for windshield repair called the Repair of Laminated Automotive Glass Standard (ROLAGS) and had it sponsored by the American National Standards Institute (ANSI). It uses the following categories for repairable breaks:

  • Bullseye,
  • Half-moon,
  • Star break,
  • Crack,
    • Short;
    • Long;
    • Edge;
    • Floater;
    • Stress; and
  • Combination break.

The bullseye break is usually the easiest to repair. The outcome is the most pleasing to the customer because it almost completely disappears. However, many techs use the bullseye to demonstrate the repair process because of the ease of repair and pleasing results. This break is usually caused by a dull, slow moving projectile. Dull projectiles cause circular breaks because of the circular “grain” in annealed glass. Only sharp, fast moving projectiles would overcome the circular “grain”, like star breaks or cracks.

A half-moon break is an unfinished bullseye and is caused by an even slower moving dull projectile. Normally half-moons are a little harder to repair because the resin must be forced to the far reaches of the break.

Photo courtesy of mswindshieldrepair.com

One method of speeding up a half-moon repair is a procedure called refracturing. Some use this method because it makes the break bigger. Since a bullseye repairs so well and the end result is almost invisible, the refracturing technique creates a full bullseye from the half-moon. A tech can use a darning needle or pointed pick and place it directly into the pit of the break. Then they can use a weighted device and tap the needle or pick until the half-moon becomes a bullseye.

This same technique can be used on both the star and the crack repairs as well. You create a bullseye at the base of the pit which makes the repair faster and easier.

Star and crack breaks are caused by sharper and faster moving projectiles. These are typically harder to repair because of the break’s narrow “legs”. It also doesn’t appear as transparent as the bullseye or half-moon. When the break is properly repaired the finished “legs” of the break appear as fine “spider web like” lines when viewed head-on.

The last category of break is the combination break, which is usually caused by a large projectile. The windshield can be hit so hard that the cone of the break is pulverized, causing a star break within a bullseye. The finished repair appears to look like a repaired star break since the bullseye disappears, but the star within the break repairs like a typical star break.

Photo courtesy of glassusa.com

Before any repairs are accepted or completed make sure your customer understands the process and what to expect. Refer to the ROLAGS Standard below: https://rolags.com/pdf/ANSI+NWRA+ROLAGS+001-2014.pdf

In my training classes I am asked frequently, “Is drilling a requirement for a good windshield repair?” The answer is no. Drilling is not a requirement.  As a matter of fact, if you can refrain from drilling a pit, the repair will appear better after the process is complete. Not drilling leaves a smaller, less noticeable pit.

You should drill the glass for one reason only. Drilling opens the pit for resin to flow freely.  Sometimes when the break is old, the pit is plugged by debris from the roadway, from car wash wax or other debris forced into the pit by the wipers. This plug hinders the flow of the resin and should be breached or removed to properly complete the repair. Some drill out the plug and others use the edge of a straight edged razor blade to pick out the plug.

I have witnessed techs attempt to drill down to the lamination to fill the break better. Some have said that is what they were taught. Do not do this! The fact is that if you drill all the way down to the lamination, the windshield’s safety has been compromised and it should be replaced not repaired.

The part of the windshield that offers the occupants the greatest barrier for safety is the Polyvinyl Butyral (PVB) interlayer. If it is punctured by hitting it with a drill bit, the PVB is no longer a restriction to ejection. It would fail at the puncture.

The proper procedure is to first use the razor blade edge to pick out the plug. If that fails, then drill the pit only to open it up. Never ever go down to the laminate. Just peck the drill bit into the pit until open and only penetrate less than half of the first layer of glass. Once that is accomplished, the resin will flow nicely. If while you are drilling, and a string of plastic comes up the drill bit, you have gone too far.

Please, DO NOT over-drill.