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The beloved all-purpose cleaner Bar Keepers Friend can work to remove a variety of tough-to-tackle stains, from rust to mineral deposits and baked-on food. And don’t let the name fool you: BKF can be put to work in places other than a kitchen setting, including bathrooms, garages, and backyards.

There are, however, certain surfaces in each of those spaces that the cleaner is not so friendly with. Here are six things that you should never clean with Bar Keepers Friend:

1. Don’t use BKF on polished stone such as marble or granite

Uh-oh! You just noticed food grime lurking on your marble or granite countertops. Before you break out Bar Keepers Friend, make sure it’s the right formula. “You should never use Bar Keepers Friend on your granite or marble countertops, as it will leave corrosive marks that will be impossible to ignore once done,” explained Jessica Randhawa, the head chef, recipe creator, photographer, and writer behind The Forked Spoon. Randhawa uses Bar Keepers Friend regularly on all of her stainless steel pots and pans, for hard water stains in her toilets, and hard water stains on her glass shower doors. 

If you do want to harness BKF’s reputation on your stone surfaces, the BKF family of products includes a Granite & Stone Cleaner & Polish, which is made specifically for granite and polished stone such as quartz countertops. It should be noted that BKF Granite & Stone Cleaner & Polish should only be used on polished stone. It is not suitable for butcher blocks, painted or lacquered surfaces, brick, slate, or grout.

2. Don’t use BKF on concrete, wood, or any other porous surface

Bar Keepers Friend is formulated to work on non-porous surfaces like glass, stainless steel, ceramic, porcelain, brass, and aluminum. But when it comes to porous surfaces — like unsealed concrete, fabric, leather, or wood — the manufacturers recommend steering clear. What classifies a porous surface? Think in terms of pores. A porous surface will allow liquids like water, to pass through or become absorbed by it. So you can clean your dutch oven with BKF, but stick with dish soap for your wooden cutting board.

3. Don’t use BKF on appliances with protective layers

To help repel fingerprints, many manufacturers apply a clear protective layer to the appliances they produce — that’s the “stainless” part of your stainless steel fridge. BKF may harm that layer due to its mineral abrasive ingredient. Instead, use Bar Keepers Friend’s specialized Stainless Steel Cleaner & Polish.

4. Don’t use BKF on lacquered, painted, mirrored surfaces, or colored grout 

5. Don’t use BKF on surfaces that can’t be rinsed well

The process of using Bar Keepers Friend looks like this: wet the surface you intend to clean. Sprinkle the cleanser onto the surface. Gently run with a wet cloth or sponge. Rinse thoroughly and wipe dry. The thorough rinsing is an important step when using BKF, and therefore it should not be used in areas that cannot be easily rinsed, such as non-drained, enclosed spaces like an oven or microwave interior. 

6. Don’t use BKF on gold or silver

Keep Bar Keepers Friend away from your precious metals. “Bar Keepers Friend will ruin other materials that it was not engineered to clean, such as gold or silver jewelry,” says Randhawa. “But it’s perfectly safe to use on sterling silver flatware.”