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Nothing beats a bright, airy bathroom, and I’m lucky to have one in my New York City rental apartment. Glossy white subway tiles cover the spacious shower walls, and light streams in through the 7-foot-tall window. But the downside? No speck of dirt goes unseen. And when the shower has a deep, tiled shelf where excess water can collect, the grout can get a little grimy. Even after scrubbing with an anti-mildew solution, the water stains remain stubborn.

This is where my latest Amazon discovery comes into play. Meet: the grout pen. You can basically think of the $9 tool as a white-out pen, but for the space between your tiles. It won’t actually clean anything, but once you’ve scrubbed the surface, the marker-like tip will add a thin layer of white waterproof paint atop your grout—giving it a fresh, good-as-new appearance. 

The process couldn’t be easier: Once you’ve cleaned the grout with bleach and a toothbrush, just shake the pen, press the tip on the surface to release the paint, color in the grout lines, and wipe up any excess paint that gets on the tile with a damp paper towel. It will dry to the touch after five minutes, and can get wet after six hours. The pen works best on nonsealed grout, so you’ll want to make sure you’re working with a porous surface that’s able to absorb the paint. 

Courtesy of Amazon

Although I used white, the pen is offered in 11 different colors—from cream to terracotta—and the whole process took me about 15 minutes. And for just $9, it’s like I have a brand-new bathroom.