How does a sponge clean with just water? A short explainer, with Happi Planet's magic eraser

The first time you rub a crayon mark off a wall with nothing but a wet sponge, it feels like a magic trick. That is the whole appeal of the magic eraser, and Happi Planet's pack of four is a good place to try one.

The listing promises it removes 100+ tough stains with just water, on walls, kitchens, bathrooms, shoes and switch boards, and says it will not scratch.

So how does it work?

Magic erasers are made of a very fine foam that behaves like extremely gentle sandpaper. When you rub, it wears away the mark on the surface rather than dissolving it with chemicals. That is why water is enough.

It also explains the two catches:

• The sponge wears down as it works. It crumbles a little with every wipe, so a pack disappears faster than you expect.
• It can dull shiny surfaces. Because it works by abrasion, pressing hard on glossy paint, polished wood or a car's paint can leave a matte patch. The "no scratch" claim is about avoiding deep scratches, not about leaving a high-gloss finish untouched.

Where it shines

• Scuff marks and pencil on matte walls
• Grubby switch boards and door frames
• White soles of sneakers
• Soap marks on bathroom tiles

Where to be careful

• Glossy painted walls and lacquered furniture
• Anything you would not rub with fine sandpaper
• Non-stick pans and car paint

How to use it

1. Wet the sponge and squeeze out most of the water.
2. Test on a hidden spot.
3. Rub lightly. Let the sponge do the work.
4. Wipe the area with a damp cloth afterwards.

Old, set-in stains may not come off at all. That is normal.

A cheap, oddly satisfying cleaning tool. Kleenest makes a very similar pack, and choosing between them mostly comes down to the price per sponge.