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If you’re buying old Lego sets at garage sales, on Craigslist, or in thrift stores, or you’ve just dug your old bricks out of the basement, you know that sticky, 20-year-old sets are no fun to play with. I just did a deep dive into the world of Adult Fans of Lego (AFOLs, for the uninitiated). And the good news is that—though it’s perhaps a little time-intensive—getting your Lego bricks back into like-new building shape is not difficult.

Washing Lego bricks can take anywhere from 30 minutes to several hours, depending on how many you have. Drying will take up to three days (mostly hands-off time).

Lego’s official advice on cleaning bricks is pretty brief: Use a soft cloth or sponge and a mild detergent, and rinse with clear water. Don’t use water that’s hotter than 104 degrees Fahrenheit. And when drying, don’t use a hairdryer, an oven, or a microwave because high temperatures can damage the plastic.

The company also specifically says not to use a dishwasher or washing machine to clean bricks—you do not want a loose Lego brick to get jammed in your machine. Though this hasn’t stopped some AFOLs from doing just that (video).

After I spent several hours watching AFOL YouTube videos, these are the most widely used methods I found, categorized into the type of cleaning required.

Dismantle all the pieces, and place any with stickers or printing (like minifigure torsos) aside. Then place your bricks inside a large plastic bin, add a few drops of mild dish detergent, and fill the container with cold or lukewarm water. Swirl the Lego soup a bit with your hands, and let it sit for around 20 minutes.

Fill a smaller bin with clean water, and transfer smaller batches one at a time to rinse (video), replacing the water each time. Use your hands to dislodge any stubborn gunk. You can also place soapy Lego pieces in a mesh bag and rinse them off in a tub or sink, or with a hose in the yard. If you’re rinsing in a bathtub or sink, make sure to have a strong drain catcher in place so errant pieces don’t clog your pipes.

As for the printed or stickered Lego, do not use the water-wash method. Instead, gently clean each piece individually with a microfiber cloth.

Spread out your wet Lego pieces on as many towels as necessary, and position one or more fans so they’re facing the damp bricks. Periodically turn bricks over with your hand to bring new ones to the surface.

Depending on the amount you’re cleaning, drying can take anywhere from one to three days. It’s a long process, but you won’t be using any damaging heat. We’ve seen some AFOLs use a salad spinner to speed up the process, but many advise against this because it could scratch the bricks.

Gently sweep your set with a clean paint brush to loosen dust. We like Purdy Clearcut brushes, and an angled tip provides more flexibility to get into corners. Smaller brushes (the kind used for working with watercolors) are good for extremely tight spaces.

As dust is dislodged, capture it with a cordless vacuum. For more control, use one that comes with a crevice attachment and a clear basin (to check for any pieces that might get accidentally sucked inside). We like the Black+Decker CHV1410L from our guide to handheld vacuums. Don’t use Swiffer-style dusters because the small fibers can get caught in the seams of attached bricks.

White, light gray, and translucent bricks can yellow over time, especially after prolonged exposure to sunlight. Soaking old white bricks in hydrogen peroxide is a popular method to brighten them up, and YouTuber JangoBricks demonstrates how to do this.

First clean the bricks with soap and water. Then, while wearing safety glasses and latex dishwashing gloves, soak discolored Lego pieces in 3% hydrogen peroxide, placed in direct sunlight.

Make sure all pieces remain submerged, and periodically wipe away any bubbles that form to ensure all surfaces are brightened. After the pieces have soaked for several hours, rinse clean and dry.

Joshua Lyon is the supervising editor of emergency-preparation and home-improvement topics at Wirecutter. He has written and edited for numerous outlets, including Country Living, Modern Farmer, The New York Times, V and VMAN, Marie Claire, Jane, and Food Network Magazine. He’s also a Lambda Literary Award–nominated author and ghostwriter. Learn more at jklyon.com.

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