How to Remove Scratches From a Mirror (and When You Can't)

Knowing how to remove scratches from a mirror starts with knowing what you're looking at. A mirror is a sheet of glass with a reflective layer and paint on the back, so a line can be in three places: on the front of the glass, in the glass itself, or in the backing behind it. Each needs a different answer, and only some can be fixed.

Below I go through how to diagnose a mark, the gentle methods glass makers allow, when cerium oxide polishing is worth trying, why toothpaste and baking soda are poor ideas on a mirror, and what to do about scratches in the backing or on acrylic mirrors. If the mirror is badly damaged, my picks for the best bathroom wall mirrors are the faster fix.

Step One: What Kind of Scratch Is It?

What you see	Fingernail test	Where it is	What to do
Fine haze or streak that changes when you clean	Nothing to feel	Residue on the surface	Clean properly; it isn't a scratch
Hairline mark you can see but not feel	Nail glides over	Light scratch in the glass	Gentle polishing may reduce it
Mark your nail catches in	Nail catches	Deep scratch in the glass	Leave, hide or replace
Clear or dark line you can see light through from the back	Front feels smooth	Scratch in the backing and silver	Seal, cover or replace; polishing won't help
Dark spots or edges, front smooth	Nothing to feel	Desilvering, not a scratch	See the desilvering guide

The Fingernail Test

Clean and dry the area, then draw a fingernail lightly across the line. If it slides over, the scratch is shallow. If it catches, there is a groove deep enough that removing it would mean removing a lot of glass around it, which is where home polishing goes wrong.

Front or Back?

Look at the line from an angle with a flashlight. A scratch on the front shows on the surface of the glass. A scratch through the reflective layer on the back often lets light through as a clear line, and the front feels perfectly smooth. Dark patches spreading from the edge are a different problem altogether, explained in my guide to mirror desilvering.

Start With the Gentle Methods Glass Makers Allow

The National Glass Association's mirror care bulletin, FB06-05, sets out what mirror manufacturers recommend, and it is stricter than most online tips. It says "no abrasive cleaners should ever be used on any mirror surface", that acid, alkali and solvent cleaners can damage the edges and backing, and that the safest cleaner is warm water with a soft, lint-free cloth.

Clean Before You Judge

Clean the mirror with warm water on a well-wrung microfiber cloth, applying any glass cleaner to the cloth rather than the mirror, and buff dry. Plenty of "scratches" are cleaner streaks, soap film or hairspray that disappear at this stage. My guide to cleaning a mirror without streaks has the full routine.

Stubborn Surface Marks: 0000 Steel Wool

For marks stuck to the surface, the NGA recommends 0000 oil-free steel wool rather than solvents. That is the finest grade, for lifting deposits such as paint specks or hard-water spots from the surface of the glass, not for grinding out scratches. Use it gently on the face only, keep it away from the edges, and stop if you see any change in the glass.

Polishing Out Light Scratches With Cerium Oxide

For a light scratch that your nail doesn't catch, the method glass workers use is polishing with cerium oxide. Wikipedia's article on cerium(IV) oxide describes it as highly valued in the optics industry for its polishing ability, working through a mix of mechanical abrasion and chemical action on the glass surface. It is the same compound sold in glass scratch-repair kits.

Know the Risk Before You Start

Polishing works by removing glass around the scratch until the surface is level. On a window that is usually invisible. On a mirror, the reflection magnifies any dip, so a polished patch can show as a wavy, distorted spot. That is why I'd only try it on light scratches, over a small area, and stop as soon as the mark fades. The NGA's advice against abrasives on mirrors is a reminder that this is a calculated risk, not routine care.

Polishing a light scratch

Clean and mask

Clean the area, dry it, and mask a small square around the scratch with painter's tape so you can see where you've worked. Keep tape and water away from the mirror's edges.
Mix the polish

Mix cerium oxide powder with water to a thin paste, following the product's directions.
Polish by hand or with a felt pad

Work the paste over the scratch with a felt pad, by hand or on a drill at low speed, moving in overlapping circles across the whole masked square rather than just the line. Keep the paste wet; glass gets hot quickly when dry-polished.
Check often

Every minute or so, wipe the area clean and look at the reflection from an angle. Stop as soon as the scratch fades, or at the first sign of waviness in the reflection.
Clean up

Rinse away all the paste with a damp cloth, dry the glass and the edges, and buff with a clean microfiber cloth.

What You Need

Supplies for cleaning first and, for light scratches only, cerium oxide polishing.

1Microfiber cloths

Puomue Microfiber Glass Cleaning Cloths, 6 Pack

Lint-free cloths for the warm-water clean that tells you whether a mark is really a scratch.

Check price on Amazon
2Cerium oxide

Cerium Oxide Glass Polishing Powder, 14 oz

Glass polishing powder to mix with water into a paste, for light scratches only.

Check price on Amazon
3Polishing kit

Kakalote Glass Polishing Kit with Felt Wheels

A kit with felt polishing wheels for a drill and cerium oxide powder, if you'd rather polish at low speed than by hand.

Check price on Amazon

Why Toothpaste, Baking Soda and WD-40 Are Poor Fixes

Toothpaste and Baking Soda

Both work, when they work at all, as mild abrasives: they wear the surface down a little. That is the same thing cerium oxide does, without its fine, controlled cut, and the NGA's line is that no abrasive cleaners should be used on mirrors at all. On a mirror they tend to leave a hazy patch that is more noticeable than the original hairline.

WD-40 and Oily Fillers

Oily products can make a fine scratch less visible for a while by filling it, but they leave a film that smears and attracts dust, and the NGA warns that solvents can attack a mirror's edges and backing. Not something I'd put on a bathroom mirror.

Is It Worth Repairing?

For a valuable, framed or antique mirror, a glass specialist can assess whether polishing is safe. For an ordinary bathroom mirror with a deep scratch, replacing the glass is usually cheaper and faster than any repair, and my guide to removing a glued mirror covers taking the old one down.

Scratches in the Backing

A scratch through the paint and silver on the back can't be polished out, because the missing silver is what you're seeing. The options are limited.

Seal It First

If the back is accessible, clean the area and seal it with paint so moisture can't get under the backing and spread the damage, which is how desilvering starts. The NGA warns that liquid reaching a mirror's edges and backing causes "black edge".

Hide It

A backing scratch near an edge can be covered by a frame; my guide to framing a bathroom mirror shows how. Painting the back of the scratch with a mirror-effect spray can soften it, but it won't match the original silver exactly.

Replace It

For a scratch in the middle of the reflection, replacement is the honest answer. A new piece of mirror glass cut to size, or a new mirror, will look better than any patch.

Scratches on Acrylic Mirrors

Acrylic mirrors are plastic, not glass, and their surface is much softer. My acrylic vs glass mirror guide explains the trade-offs.

Use Plastic Polish, Not Glass Products

Light scratches in acrylic can be reduced with a polish made for acrylic and plastics, applied with a soft cloth. Cerium oxide and glass kits are designed for glass and can haze plastic.

Prevent the Next One

Clean acrylic with a soft, damp microfiber cloth only, never paper towels or anything abrasive, and keep rings and jewelry away from the surface when you wipe it.

Sources

National Glass Association: Proper Procedures for Cleaning Flat Glass Mirrors (FB06-05, 2019) No abrasive cleaners on any mirror surface; warm water and a lint-free cloth; 0000 oil-free steel wool rather than solvents for surface marks; solvents, acids and alkalis damage edges and backing; wet edges cause black edge.
Wikipedia: Cerium(IV) oxide Valued in the optics industry for polishing, through mechanical abrasion and chemical interaction.

How do you fix a scratched mirror?

Clean it first, because many marks are residue. If the scratch is light enough that a fingernail doesn't catch, cerium oxide polishing over a small area can reduce it. Deep scratches and scratches in the silver backing can't be polished out: hide them with a frame or replace the glass.

Will toothpaste remove scratches from glass?

It can soften a very fine mark on ordinary glass because it is a mild abrasive, but it is a poor choice for a mirror. The National Glass Association says no abrasive cleaners should be used on mirrors, and toothpaste often leaves a hazy patch that shows more than the scratch.

Does WD-40 really remove scratches?

No. An oily product can make a fine scratch less visible for a while by filling it, but the scratch is still there, and the film smears and collects dust. On a mirror there is another reason to avoid it: the NGA warns that solvents can damage a mirror's edges and backing.

How do you repair the silver on the back of a mirror?

You can't restore missing silver at home. Seal the scratch with paint so moisture can't spread the damage, hide it with a frame if it's near the edge, or have the mirror professionally resilvered or replaced. Mirror-effect spray can soften a mark but won't match the original.

Is it worth repairing scratched glass?

For a deep scratch on an ordinary mirror, usually not: replacement is cheaper and looks better. Repair makes sense for light scratches you can polish yourself, or for antique and framed mirrors where the glass has value, and then a glass specialist should look first.

Keep reading: How to clean a mirror without streaks · Mirror desilvering · Acrylic vs glass mirrors · Best bathroom wall mirrors