How To Properly Polish Scratched And Stained Glass On Your Classic

Glass Polishing

How often have you experienced driving your car at night, and while cruising down the road, you notice that the headlights from oncoming traffic seem to have a strange reflection through your windshield. For some reason, the light seems to scatter, and sometimes, even get a “star-like” appearance. In case you hadn’t realized it yet, it’s time to either replace your windshield, or at a minimum, give it a good polishing.

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Before you polish, the window needs to be cleaned. It will be impossible to polish the glass if you keep grinding dirt into it.

Some of you might have never heard about polishing glass, but the premise has been around for a long time. Cerium oxide used to be the polish of choice for glass that had light scratches or embedded debris. But since that material is getting harder to come by, substitute compounds are being utilized.

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Scratches might not look very bad, but when light hits them, it can cause vision problems.

Before you can even begin to polish any scratches out of the glass surfaces in your car, you must first determine how deep the scratches are. Essentially, if you can run your fingernail across the scratch and it “catches,” it is quite possibly too deep to be removed by polishing. It sounds strange, but in this case, you must first sand the scratch. Eastwood Restoration Products has different levels of glass polishing kits to help you, depending on your needs.

Kit number 12525 is a do-it-yourself glass polishing kit that contains what Eastwood calls Diamond Fast Powder, and can be used to fix very mildly-scratched glass like those with that annoying windshield wiper haze. This kit is great for windshields that are not deeply engraved. If you can run your fingernail over the scratched area of your windshield, and you’re lucky enough that your fingernail doesn’t “catch” on the scratch, this kit will work fine for you.

Alternatively, if you can feel the scratch as your fingernail crosses over it, the scratch is too deep to simply be polished. If this is the case, Eastwood also has its Pro Glass Polishing Kit for deep scratches. Kit number 12526 supplies you with some extra items that you will need, like sandpaper. That’s right, we said sandpaper, to help repair the glass.

The Eastwood kit comes with everything you need, just add water to a small amount of the polishing powder, and mix to a toothpaste-like consistency.

It might sound strange, but when deep scratches are present, you must first “sand” the scratch before it can be polished. To do this, you will not need a grinding wheel, but rather, the silicon-carbide sandpaper that comes with the Eastwood kit.

Use the polish sparingly, keep the area being polished wet, and no matter what else you do, keep the polishing disc flat on the glass surface.

The coarseness of the sandpaper grit used to grind out the scratch will depend on the actual depth of the scratch. The kit comes with three different grit papers, and it is best to use the finest grit you can to sand out the scratch.

This polishing kit is just the thing for a windshield or other window that has gotten stained or has a slightly-hazed appearance to it. – Aaron Lindquist

The Eastwood glass polish works a lot like a polish you would normally use on a painted surface. It contains abrasives that remove imperfections, leaving behind a smooth surface, and in the case of glass, a surface that is perfectly clear. It is important to understand exactly what a glass polish can and cannot do. This is not a miracle kit that can save any piece of glass. But, if your glass is plagued with water spots, is etched by splattered bugs, and has very light scratches like those thrust upon your car by the windshield wipers, this polishing kit might be just what you need.

“This polishing kit is just the thing for a windshield or other window that has gotten stained or has a slightly-hazed appearance to it,” said Aaron Lindquist of Ratchet Garage. We don’t recommend a glass polish for trying to remove deep scratches or stone chips, as those tasks are best left to those guys that do it for a living. Scratches in a window are not only annoying, but can obstruct your vision, which makes driving dangerous. In a perfect world, scratched glass would not be an issue, but life prevents a perfect world, so we have to deal with them.

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If you can catch your fingernail on the scratch, it will need to be sanded.

In order to repair a mildly-scratched windshield, here are some steps to help you accomplish the task. Like we said, if you are trying to repair a large scratch, this kit might not be what you need. Let’s face it, you don’t want to make it worse.

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The sanding paper in kit 12526 comes in three grits; course, medium, and fine.

Lindquist is a young Chevy enthusiast that has been working on, and improving, his Nova since high school. The car has come a long way since its early days, but lately, he has been noticing the quality of vision through the glass is deteriorating. The glass isn’t in terrible shape, and we figured that a good polishing with Eastwood’s polishing kit would make the need for replacements go away.

We decided to work on a small area of the rear glass, as we noticed some slight scratches and swirl marks. To begin, we first washed the rear window thoroughly with soap and water so we had a clean surface to work with. If you don’t clean the glass before you start polishing, you risk grinding the dirt and debris that you didn’t remove, deeper into the glass. After we washed the glass, we rinsed all of the soap residue away, and then dried the window before applying the rubbing compound.

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When sanding, always start with the finest grit possible.

With the glass cleaned, we next masked off the area around our work area, and then mixed up some polish. The Eastwood polish comes in powder form, and you need to add water to create the polish. Don’t mix the entire container with water, place a small amount of the powder in a cup, and mix with water.

We found this old truck door with a rust stain on the vent window that wouldn't come off, even after using lacquer thinner and steel wool. The polishing kit made the vent glass look new.

When properly mixed, the paste will have a toothpaste-like consistency. Not only should the area being polished be clean, but you will want to make sure that it is always wet. When polishing any surface, you are creating heat through friction, and glass does not like heat.

What You Will Need

  • Cordless drill
  • Polishing kit
  • Glass cleaner
  • Clean rags
  • Container for mixing polish
  • Safety glasses
We next applied the Eastwood polish onto the area we planned to “repair,” and with the polishing head mounted in our trusty cordless drill, Lindquist started polishing. According to the Eastwood instructions, do not use a polisher with an RPM of more than 1,500. We followed the instructions in the kit, and after we had polished the scratch, we cleaned the area to see the results. We soon learned, however, that we would need to actually do some sanding to remove our scratches.

Three levels of coarseness of sandpaper are supplied with the kit, and once again, we followed the instructions for sanding our glass. By using the finest grit paper first, you can judge how well it works, and then step-up to a coarser grit if needed. Sand at a low RPM, and keep the surface wet. After sanding, clean the area and check your results. If sanding has removed the scratch, follow up with polishing the glass, and then consider it done. If the scratch is still present, additional sanding will be required.

These two side-by-side images show the results we got on our hazy and mildly-scratched glass. Deep scratches will require a lot more time and sanding.

The success of your polishing job will depend upon how badly your window is scratched. Some scratches, like ours, might need a second application sanding and polishing. But, even if you have to apply this process twice — or even a third time — isn’t it a lot less expensive than having to replace the window? If the idea of polishing glass sends chills up your spine, we’re here to tell you it can be done safely. And, you can do it yourself!

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About the author

Randy Bolig

Randy Bolig has been working on cars and has been involved in the hobby ever since he bought his first car when he was only 14 years old. His passion for performance got him noticed by many locals, and he began helping them modify their vehicles.
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