How to Clean the Black Edges on Your Carpet

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Filtration soiling is why the edges of your carpets turn black and dingy. Use these steps to get them clean again.

Overhead of a vacuum cleaning the black edge of a carpet at the base of a wall.

Have you ever noticed the edge of your carpets look darker than the rest? Maybe you shampooed the carpet, hoping to get rid of them, but they didn’t budge. The good news is that this is a common problem, so it doesn’t mean you’re bad at cleaning or that your home’s a mess. The bad news is that vacuuming won’t eliminate them. But you can get them out with effort, and below you’ll also learn steps to help prevent their return.

Why Do the Edges of Carpets Get Black?

Dark lines develop on your carpet when air enters rooms faster than it can exit. If air can’t escape through returns or doorways, it seeps through gaps beneath baseboards and stair treads where ultra-fine dirt particles get caught on the carpet fibers. This problem is more common in older homes since builders now use housewrap beneath siding and add a gasket or strip of closed-cell foam at the sill plate to stop filtration soiling.

Before You Begin

Cleaning filtration soiling isn’t a quick chore, so many homeowners hire professionals. Not all carpet cleaning employees are trained to clean draught marks properly. Unfortunately, you won’t know this until you’ve paid the bill because carpet stains can reappear after the carpet dries. To eliminate the black lines on your carpet edges yourself, follow the steps below. Since this involves dampening your carpet, you’ll need to set aside an afternoon for each room or work in sections. Do not walk on carpeting until it’s dry.

Steps to Remove Filtration Soiling

Equipment and Materials

  • A vacuum cleaner with a crevice tool and brush attachment
  • Scrub brush
  • Baking soda (bicarbonate for UK readers)
  • Spray bottle
  • Water
  • Hydrogen peroxide or rubbing alcohol
  • White cloths
  • Carpet shampooer or steam cleaner

1. Vacuum the area: Use the crevice tool to clean the dark area at the edge of your carpet. Then, switch to the brush attachment and vigorously brush the area to loosen any sooty residue.

2. Apply baking soda: Sprinkle a thin layer of baking soda on the discolored area. Use the scrub brush to rub it into the fibers to bond with the sooty carbon soil. Wait an hour, then vacuum it with the crevice attachment.

3. Spray: For white or ivory carpets, combine 3 parts water with 1 part hydrogen peroxide in a spray bottle. For all other carpets, combine 3 parts water with 1 part isopropyl (rubbing) alcohol. Mist a 3-foot section of the rug just enough to dampen the fibers. Do not drench the area, or you’ll get the underlay wet, which can destroy the adhesive. Wait 10 minutes for the spray to begin loosening the sooty mess.

4. Blot: Use a clean white cloth to blot the area. Change cloths as needed, so you’re always working with a fresh section. Do not rub — the idea is to transfer the dark grime from your carpet onto the cleaning rag. Reapply the spray as needed, so the carpet stays damp but not overly wet while you work. Once you’ve finished blotting the area, let it dry for at least 24 hours, and then vacuum again with the crevice attachment.

5. Shampoo: The spray solution will have loosened the grime but may not completely remove it. To eliminate any remaining dark lines, shampoo your carpet using a process that removes greasy soil. Do not walk on your carpet until it’s dry.

How to Keep the Edges of Carpets from Turning Black

It’s important to understand that vacuuming isn’t enough to eliminate those dark lines on your carpet’s edges. If your home has an HVAC system but does not have a gasket or foam at the sill plate, filtration soiling is bound to occur. But there are steps you can take to minimize or delay it.

1. Vacuum often. The less time filtration soil sits bonding with your carpet’s fibers, the easier it is to get out. So, vacuum and use the crevice attachment at the base of your walls at least once a week. Also, make sure you know how to vacuum correctly, so you’re getting all the dirt out.

2. Don’t add pollutants to your home’s air. Open your windows daily for at least 10 minutes to allow fresh air into your home. Don’t smoke indoors, and run your stove’s hood filter fan when you’re cooking. Keep your range hood filter clean, so it works properly, too. Choose soy candles, which produce very little soot, and trim candlewicks before burning them. Clean your fireplace and have the chimney inspected annually to ensure creosote is not blocking the flue.

3. Keep dust under control. The less dust in your home’s air, the fewer particles collect in the carpet at the base of your walls. So, reduce dust in your home by routinely cleaning soft furnishings, curtains, and carpets. At least once a year, have your home’s HVAC system inspected and cleaned. Change your furnace filter monthly and clean your home’s air ducts and registers seasonally to reduce how much dust your system blows around.

4. Promote good airflow. Do not close off rooms or leave doors shut, since this encourages filtration soiling along the walls. Also, make sure your furniture does not block cold air returns or vents, both of which are needed for your home’s air to circulate properly.

Keep in mind that there’s no way to completely avoid filtration soiling in older homes with an HVAC system and carpeting. You can remove it using these steps, but even if you buy a new carpet, it will develop black edges around the base of the walls, too. When ready for new flooring, switch to wood, tile, or LVP, and use area rugs as needed for comfort. You’ll no longer have black edges on your carpets, and your home will be much easier to clean.

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