Mr. Clean Magic Erasers really live up to their name: They seem to scrub away dirt, grime, and muck while you barely lift a finger. However, much as we’d all love it if a Magic Eraser got any cleaning job done perfectly 100 percent of the time, you’re not actually supposed to use them on every single surface. In fact, they could even make a few areas of your home worse in the long run.

What is in a Magic Eraser that makes it work?

We all know about the power of Magic Erasers (Buy from Amazon, $13.24 for a pack of 10), but did you ever wonder about what they’re actually made of? Despite looking like a sponge, these products are made of what’s called melamine foam, which can also be used for temperature and sound insulation. It may feel smooth when it’s in your hand, but on a microscopic level, it’s essentially hard melamine resin crystals encased in air bubbles. Similar to when sandpaper buffs out rougher edges, these tiny pieces of melamine resin scrape at surfaces to polish away messes.

What can you not use a Magic Eraser on?

The problem is that these tiny, grainy resin crystals can ruin some of those surfaces, similar to how you’d never use sandpaper on certain parts of your house. Like sandpaper, Magic Erasers can mess up the appearance of anything with a seal, varnish, or other protective top coating and even scrape it away over time, leaving the material beneath exposed.

Magic Erasers can also wreak havoc on stainless steel and weaken it. Just ask this mom who used one on her refrigerator and accidentally destroyed the top coating. Whoops!