How to remove scratches from glass, and when a scratch can't be fixed

Builders' grit dragged across a new window, a ring scraped down a shower screen, a pet clawing at a patio door: scratches on glass are common, and the internet is full of miracle fixes. Some work on the faintest marks. None of them work on a deep scratch. This guide tells you which is which before you spend an afternoon rubbing.

The short answer

Run a fingernail across the scratch. If your nail does not catch, it is a surface scuff that can usually be polished out with a glass polishing compound such as cerium oxide. If your nail catches, the scratch is too deep to remove safely at home, and the pane or sealed unit should be replaced. Never try to polish out scratches on toughened or coated glass beyond the lightest scuff.

Step 1: the fingernail test

What you feel	Scratch depth	What to do
Nothing, visible only in certain light	Surface scuff	Clean, then polish gently
Nail just catches	Light scratch	Professional polishing may help on plain glass
Nail clearly drops in	Deep scratch	Replace the pane or sealed unit
Scratch with a chip or crack	Damaged glass	Replace, especially in a door

Step 2: make sure it is a scratch

Plenty of "scratches" are not scratches at all:

• Paint, cement or plaster splashes look like marks but scrape off with a new razor blade held flat, on wet soapy glass.
• Hard water marks on shower screens and outside panes come off with diluted white vinegar.
• Marks between the panes of a double glazed unit cannot be reached at all. If they are misty, see the failed double glazing tests.

Step 3: polishing out a light scuff

For plain, uncoated glass with a scratch your nail does not catch:

1. Clean the glass thoroughly so grit does not make new scratches while you polish.
2. Mask round the area with tape, and protect the frame and gaskets.
3. Mix cerium oxide powder with water to a creamy paste, or use a ready-made glass polish.
4. Polish with a felt pad by hand or on a low-speed drill, in small circles, keeping the paste wet and the pad moving.
5. Check often. Wipe clean, look from several angles and stop as soon as the mark fades. Overworking one spot leaves a lens-shaped distortion.
6. Clean off all the paste.

Toothpaste and baking soda pastes work on the same idea, but much more weakly, and only on the faintest marks.

Worth knowing: heat builds up quickly when polishing with a drill. Keep the speed low and the area wet. Heat on glass, especially near the edge of a sealed unit, can crack it.

What not to do

• Do not polish coated glass such as low-e, self-cleaning or tinted glass. You remove the coating and leave a permanent patch.
• Do not use abrasive pads, wire wool or scouring cream on glass. They add more scratches.
• Do not rely on WD-40, oils or car wax. They only hide a scratch until the next clean.
• Do not polish toughened glass in doors and shower screens beyond a light scuff.

When replacing is the better answer

A deep scratch weakens the surface, and on a large or toughened pane that is a real concern. In a double glazed window, we replace just the sealed unit in the existing frame, so nothing else changes. Single panes can be cut to size in our Wood Green workshop. Doors and low panes should get safety glass: see where safety glass is required.

Scratched on a new installation? Photograph it before anyone touches it and raise it with the installer straight away, because scratches are much easier to settle on handover day.

Send a close-up photo on WhatsApp with a coin beside the scratch for scale, and we will tell you whether it will polish or needs new glass. Or call 07915 903485.