Finding black speckles on grout or a fuzzy patch on the shower curtain is gross—and usually the first instinct is bleach. But bleach is harsh on porous materials and can produce overpowering fumes in a small bathroom. That’s why turning to borax to kill mold is a practical, low-fuss alternative. A plain box of borax, found near the laundry detergent in most supermarkets, works surprisingly well and costs only a few dollars.
Borax is also called sodium tetraborate. It’s a naturally occurring mineral powder that professionals have used for decades as a mild disinfectant and fungicide. When mixed with warm water, it creates an alkaline solution that breaks up mold colonies and discourages them from settling back in. It doesn’t cause the strong fumes that bleach does, though you still want to keep it out of reach of children and pets. If you have color-fast tiles, glazed ceramic, metal, or glass, borax is perfectly safe to use.
What you’ll need
- 1 cup borax
- 1 gallon warm water (or 1 cup water + 2 tablespoons borax for a small area)
- A clean spray bottle
- Soft scrub brush or old toothbrush
- Sponge or microfiber cloth
- Rubber gloves
How to clean mold with borax
- Prepare the area. Open a window or turn on the exhaust fan. Always wear rubber gloves, and if you wear contact lenses, it’s smart to put on a pair of safety glasses too, since the powder can be dusty.
- Mix the solution. Use warm water so the borax dissolves fully. Stir it well before pouring into a spray bottle. Don’t combine borax with bleach, vinegar, or commercial cleaners—mixing cleaners can create harmful gases or make the solution less effective.
- Spray the moldy spot. Generously coat the affected area and let it sit for about 5–10 minutes. This gives the mineral solution time to penetrate the surface and begin breaking down the mold’s root structure.
- Scrub gently. Use your soft brush to scrub away the visible mold, working in small circular motions. If the mold is in a tight corner, an old toothbrush works well. You don’t need to rinse the area with plain water afterward—the residue left behind is actually what helps keep mold from returning.
- Wipe off excess, then dry. Use a clean, damp sponge to wipe away any remaining grime and the majority of the borax solution. Dry the surface with a separate cloth. Air-drying is best, so leave the room’s fan on for another hour if you can.
🫧 Note: Borax leaves a very slight powdered film on surfaces. On glossy tiles, wipe the treated area once more with water if you don’t want that residue. For porous materials like untreated wood or drywall, scrubbing won’t remove mold that’s already penetrated inside. In those cases, the material often has to be removed and replaced.
Borax is not a miracle cure for rot or deeply embedded mold, but for routine bathroom and kitchen mold, it is a genuinely useful tool. Keep a spray bottle pre-mixed and labeled in your cleaning bin, and inspect damp corners once a month before they develop that telltale musty smell. A little regular attention now is far easier than a weekend scrub later.
Related Terms:
- Borax to Kill Mold mites