Feint Scratch On Windscreen

[Habu]

I've picked up a feint scratch across the windscreen courtesy of the nearside wiper. I've tried removing it using glass polish to no avail. Does anyone have any experience of removing a fine, albeit quite long, scratch across the glass? I have an assortment of paintwork swirl removers such as Meguiars Scratch-X 2.0 and Meguiars Ultimate Compound but I'm not sure if they would be suitable on glass.

Any suggestions welcomed.

Cheers

Peter

[rayaans]

which glass polish have you Used? Glass won't polish by hand, it's too hard, you'll need to machine it to get a result

[johnno]

I had exactly the same problem with my previous IS250C. I took it to the dealer (Lexus Chester) and they managed to remove it completely. Service manager told me that they used jewellers rouge, whatever that is! Great result and they wouldn't even charge me for doing it.

[bluenose1940]

What about a 'Windscreen repair) free via your car insurance. If they can fill a chip so that it is virtually invisible i would have thought that they can do the same with a scratch. Might well be worth an ask anyway.

I had a chip repair on my old Rover 75 and when he'd finished you couldn't see nor feel it. You pay an excess on windscreen replacement but nothing on a repair.

[matt-c]

It will have to be a very faint/light/surface blemish to be removed by polishing. We use specifically designed polishes, and they won't get out most scratches. Jewellers rouge used to be the trick back in the day, but glass has come on leaps and bounds since then, and it's composition, for better optical quality and strength, all the while being thinner and lighter, is much tougher than it used to be, hence why scratches generally don't come out. Rouge is still pretty effective for "metal marks" (where a mark is caused by transference of metal material on the glass, rather than something/object marring the surface or "scuffing" away the glass finish)

If it's a very light blemish then you might be able to get it out. Anything too marring will need to be sanded out and repolished. Problem with that is you're removing an area of the glass, so you will have a void. Even a slight void will impair the glass' optical quality and be noticeable with wipers.

My advice is take it to one of the car-park stone chip guys, and bung him a fiver to try using the resin polish. If that doesn't work, then I'd leave it as it is, as you'll probably only end up making it worse. I'd need to see it in person to advise you better, so this is all I can do/say blindly

[matt-c]

What about a 'Windscreen repair) free via your car insurance. If they can fill a chip so that it is virtually invisible i would have thought that they can do the same with a scratch. Might well be worth an ask anyway.

I had a chip repair on my old Rover 75 and when he'd finished you couldn't see nor feel it. You pay an excess on windscreen replacement but nothing on a repair.

A chip repair is a different thing. That is filling a crater and crevice with a specially designed liquid resin, that is forced in under pressure, then cured hard with UV light. It's then cut back to surface level so it cannot be felt (so as not to foul the wipers). You cannot fill scratches with it, as the resin would have nothing to grip to. Easy way to imagine it is like tree roots - the centre crater is where the trunk is, and the cracks spreading off from it are like the roots. The resin flows though the trunk and into the roots, and once cured is harder than the glass itself, but it can't come out because it's larger than the crater in the glass. This is why surface "chips" that aren't actually chips, can't be repaired. They can be filled with something called "pit-fill", which is a liquid "cap" put over the top of the resin (this serves two purposes - 1) it traps the resin inside the glass before it's set hard with the UV light and 2) it's not as hard as the resin, so responds better to cutting back and polishing), but pit fill won't stay in a surface chip or scratch unless it's mixing with the resin - it has next to no bond qualities. There's nothing you can fill, or "line" a scratch with that has any strong enough bonding qualities that won't actually make it look worse and impair the optical quality of the glass.

[bluenose1940]

matt-c, I bow to your superior knowledge. Having your sort of chaps as fellow members on forums like this is absolutely invaluable.

Thank you for the insight, much appreciated.

[Rabbers]

There is an Italian product called TREMILLIMETRI which is probably available online somewhere. This is a non-

abrasive paste used in tiny amounts as an alternative to jeweler's rouge (i.e. iron oxide) to manually polish minor

scratches off most smooth surfaces, and although it is advertised as effective mainly on metals and plastics, I

have used it successfully on car and even wrist-watch glass. As a rule of thumb, if you can feel the scratch when

passing a fingernail across it, it will be too deep for this particular product to work.

[fjcfarrar]

If the scratch is so faint that you can see it in sunshine but can't feel it at all with a fingernail, jewellers rouge (available on eBay etc.) may minimise the scratch without doing harm. You may need to use a power buffer/mop because the rouge is a very fine abrasive and cuts very slowly when applied by hand. It is also very difficult to get splashes of the rouge out of clothing.
The compounds used to make modern windscreens may be tougher and thinner; but particularly when the windscreens are new and before the action of light etc. on the glass effectively modifies the surface, are much more vulnerable to scratching by whatever the wipers etc. pick up from microscopic grit and brake-dust particles thrown up from roads.