Every restorer gets asked the same question on site, usually with a fingernail already in the groove: is this one too deep? There is an honest answer, and it is not a number in millimetres. A deep glass scratch stops being repairable when the amount of surface that would have to come off is more than the panel can give up without showing it.
Why the limit is not a depth
Correction works by lowering the surface around a scratch until it reaches the bottom of the groove. So the real variable is not how deep the line goes — it is how wide an area has to be brought down with it to keep the pane optically flat. Go down a long way over a small patch and you have cut a lens into the window: everything seen through it bends, and that is permanent in a way the scratch never was.
That is why one long, shallow scratch across a shopfront is often easier than a short, deep gouge in the middle of a small pane. The gouge forces removal over a wide radius to blend, and the pane may not have the thickness to spare.
The tests that decide it
The fingernail. Drag a nail slowly across the mark. Slides over with a faint drag: fine scratching, routine work. Drops in and stops: deep, more removal, more blending, a bigger job. This is the single most useful thing you can tell us over the phone, and it beats any photograph.
Raking light. Hold a flashlight nearly flat against the pane and look along the surface. Fine scratching throws a thin bright line that vanishes as the light moves. A deep trench holds a hard shadow at every angle.
The back of the pane. Feel the other side at the same spot. A nail catch on both faces means two separate scratches, not one deep one — and two shallow marks are far better news than they look.
The cases where depth stops mattering
Some panels are out regardless of how the fingernail test goes, and it is worth knowing which before anyone quotes:
- Chips, not lines. A rock chip is a crater with a cone under it. Removing enough surface to reach the bottom of that cone is not sensible on any pane, and in a driver’s field of view we will not polish at all.
- Coated glass. Low-e, mirrored and anti-reflective faces come away with the first pass. Deep or shallow, if the damage is on the coated side, polishing is the wrong answer.
- Laminated glass down to the interlayer. Once the scratch has gone through the outer ply, the plastic underneath is exposed and no amount of surface work reaches it.
- Failed double glazing. Haze between two panes is a blown seal. Nothing done to an outer face touches it.
- Tempered glass with heavy scribing. Tempered panels carry built-in surface compression, and deep scribing on a heavily stressed panel is a case we look at carefully before agreeing to it rather than after.
- Windows with glued-on grilles. Simulated divided lite leaves no room to bring a head to the glass beside the bars. Those are quoted as replacement by rule, whatever the scratch looks like.
What “too deep” really costs you
Being told no on a panel is not the worst outcome. The worst outcome is a panel that was borderline, got worked anyway, and now carries distortion instead of a scratch — because that cannot be undone and the pane has less thickness left than when it started. A contractor willing to say the word replacement is the one to keep.
Everything that moves the figure on the panels we do take — depth, glass type, panel count and access — is broken down in what glass scratch removal actually costs in Los Angeles.
Do not soften it up first
Abrasive home remedies rubbed by hand over a deep scratch leave a hazy halo around it, and that halo then has to be corrected along with the original damage. It converts a small repair into a large one. The list of products that do this — and why each one does — is in glass scratch myths that make damage worse.
How to get a straight answer on your panel
Do the fingernail test, then send three photos: the whole panel in frame, one at a low raking angle so the damage catches the light, and a close-up of the deepest mark. Tell us the glass type if you know it, how many panels, and roughly what size.
Call or text 818-356-1345, email info@theglassrestore.com, or start from our glass scratch removal page. If your panel is one we should not touch, you will hear that — it is cheaper for both of us than finding out on site.
Working on it yourself? Read when a DIY kit is enough and when you need a pro before you start. The DIY kit is $279 and the commercial kit is $499; neither changes the limits described above.