Why Do Carpet Stains Resurface After Carpet Cleaning?

The stains that just won’t go away

Many people have heard the stories: you pay for professional carpet cleaning, only to see some stains pop back up over the next few days. Unfortunately, a stain resurfacing is a real possibility — and it’s especially common with pet stains. Here’s exactly why it happens and which stains are most likely to return.

Capillary action, cohesion, and carpet fibers

Water can travel up a small tube or fiber on its own through a process called capillary action — think of the classic celery-in-red-water experiment. Water does this because of cohesion: water molecules are “sticky” and attracted to one another, so when one moves up a fiber, others follow.

What does that have to do with carpet cleaning?

When carpets are steam cleaned, a small amount of moisture stays trapped in the padding underneath for a while afterward. If that padding is dirty, the trapped stains can work their way up to the surface via capillary action — a process called wicking. Walking on freshly cleaned areas compresses the padding like a sponge, releasing moisture and increasing wicking, which makes a stain more likely to resurface.

Which stains are most likely to resurface?

Liquid-based stains are the most likely to return, because they’re the ones that soak into the padding — drinks, mud, and pet accidents top the list. Any stain that has worked into the padding can resurface, though. If our technicians think a stain is likely to wick back, they may recommend a sub-floor treatment, or in the worst cases replacing the padding (much cheaper than replacing the carpet) to guarantee the stain won’t return.

Choose high-quality padding

The best way to prevent resurfacing is quality padding. Not all padding is equal — spending a few extra cents per square foot makes a big difference. If you go with cheaper shredded-foam padding, get one with a moisture barrier on top. The gold standard is thick solid-foam padding with a moisture barrier (such as Scotchgard foam or memory foam with a Teflon surface protector): comfortable, water-resistant, and designed to resist mold, mildew, and bacteria. Next time you shop for carpet, pay as much attention to the padding as the carpet itself.