You might’ve seen a viral hack here and there about how best to sanitize your makeup sponges, but we’re here to tell you the actual best tried-and-true ways. If that doesn’t scare you into cleaning things up (it should), this buildup can also mess with the sponge’s function: Dirty, overused sponges just don’t work as well as freshly cleaned ones. But in case you just know you’re not going to be that diligent, makeup artists Jenny Patinkin—who boasts her own collection of sponges, brushes, and tools—says every three to four uses is OK, or “at least once a week!” And in case you want some sensorial cues it’s time for a rinse, Patinkin looks for these: “There’s the obvious visual cue of how dirty the sponge looks. If you use your sponge damp, you’ll also start to feel it squish differently when there’s too much product built up on the inside,” she says. “And this is really gross; very dirty sponges will start to smell weird. Please, please wash your sponges before that happens!” As for the soap, there are plenty of sponge-specific washes on the market, but any gentle option will do in a pinch. “Any fragrance-free cleanser will do,” says Patinkin. “I personally prefer to stay away from sodium lauryl sulfates because that’s a detergent that runs off into our waterways, and I avoid fragrances because they can damage the sponge foam.” She goes on to explain that more severe or harsher soaps (like traditional shampoos or dish detergents) may cause issues in another way: “One of the most important steps is you must fully rinse out the soap,” says Patinkin. “If you don’t fully rinse, your sponge can get kind of hard and dense. Liquid dish soap and shampoos do get sponges clean, but there are so many foaming agents in them, they can be really challenging to fully rinse.” Silva agrees, noting that some soaps run the risk of shortening the life span of the sponge: “If you are using anything that isn’t alcohol-free and gentle and was not formulated for makeup tools, you risk breaking down the foam.” While there are several varieties out there, most more or less function the same: Apply soap and water, grab your pad, and move the sponge around in circular motions, being mindful to work all the sides. Just be careful of how hard you are doing your movements. “You have to be careful because they can tear the delicate surface of the sponge,” says Patinkin. “I have seen and heard of so many different, crazy ways that people have tried in order to clean their blenders. And I have tried them all myself, just to see if I was missing anything,” says Silva. “The first time I tried this, I set my blender on fire. So I don’t recommend it.” Patinkin notes that it’s not just that it’s unnecessary, but there might be real reasons you don’t want to use it. “Most sponges are made from antibacterial foams, so the idea that heating them up will make them more sterile is not accurate,” she says. “And many sponges are treated with stuff like flame retardants, and I certainly can’t recommend cooking them up with microwave rays. I’d be concerned that it might alter the chemical composition.” (And on that note: Look for clean sponges that are made with ingredients you trust.) You can also speed up the drying process by removing water with a clean towel: “I also recommend using a towel or washcloth to blot the excess moisture out of the sponge before you set it down to dry.”