Borax Mold Guide: Safe Mold Removal With a Simple Mineral

Does borax kill mold? Absolutely. And if you're a homeowner looking for a mold killer that’s safe, affordable, and effective—borax might be your best friend. As a licensed mold assessor, I’ve seen borax outperform a lot of commercial products when used properly.

Let’s break down why borax works, how to use it on walls, wood, and clothes, and when it’s not enough on its own.

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✅ What Is Borax and How Does It Kill Mold?

Borax (sodium tetraborate) is a naturally occurring mineral salt. It's not the same as baking soda or boric acid, although they all belong to the boron family.

Here’s what makes borax a mold killer:

• High pH (alkaline) — Mold hates high pH environments. Borax disrupts its growth.
• Dehydrates mold spores — It removes moisture from mold cells, killing them.
• Prevents regrowth — Borax leaves a residual film that helps inhibit mold from returning.

🧪 EPA Note: While borax isn’t registered as a fungicide by the EPA, it is considered a safer cleaning agent that can clean mold and prevent regrowth on hard surfaces. [EPA Safer Choice]

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🧼 How to Kill Mold with Borax

Here’s a step-by-step guide to using borax for mold cleaning.

🧪 Borax Mold Cleaning Recipe

Ingredient	Amount
Borax	1 cup
Warm Water	1 gallon
Spray Bottle	Optional (for walls and wood)
Scrub Brush	Required

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✅ Instructions

1. Mix 1 cup of borax into 1 gallon of warm water. Stir until fully dissolved.
2. Apply solution to the moldy area using a cloth, sponge, or spray bottle.
3. Scrub the surface thoroughly to remove mold stains and spores.
4. Do not rinse. Let the borax solution dry on the surface to prevent regrowth.

⚠️ Do Not Use on Porous Materials Like Drywall
Borax is water-based. On drywall or insulation, this may feed mold. Use a dry cleaning method or call a professional.

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🏠 Where to Use Borax for Mold

Here’s how borax performs on common household surfaces:

Surface	Safe to Use Borax?	Notes
Walls (non-porous)	✅ Yes	Avoid if drywall is soaked or compromised
Wood (sealed)	✅ Yes	Great for studs, joists, and furniture
Clothes	✅ Yes	See instructions below
Carpet	❌ No	Too wet—use a HEPA vacuum instead
Tile & Grout	✅ Yes	Great on bathroom surfaces

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👕 Using Borax to Remove Mold From Clothes

Moldy laundry? Borax can help.

Washing Machine Method:

1. Add ½ cup of borax directly into the washer (or dissolve in hot water for front loaders).
2. Add detergent and run the hottest cycle safe for the fabric.
3. Dry clothes in the sun if possible for UV mold-killing power.

☀️ CDC Tip: Sunlight and heat are effective at killing remaining mold spores on fabrics. [CDC - Mold Cleanup]

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🔎 Does Borax Kill Black Mold?

Yes—borax kills black mold (Stachybotrys chartarum) on non-porous surfaces. It may not fully penetrate drywall or hidden cavities.

If you're dealing with musty odors, extensive staining, or recurring growth, it’s time to call in a licensed mold professional for testing and remediation.

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📏 How Long Does Borax Take to Kill Mold?

You should leave borax solution on moldy surfaces for at least 24 hours without rinsing. That allows it to fully dry and leave behind an alkaline residue that discourages regrowth.

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🧂 Is Borax a Mineral?

Yes—borax is a natural mineral mined from dry lake beds and refined for use in cleaning products. It’s commonly found in laundry boosters like 20 Mule Team Borax.

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⚠️ Borax vs Bleach for Mold

Feature	Borax	Bleach
Kills mold	✅ Yes	✅ Yes (surface only)
Prevents return	✅ Yes	❌ No
Safer indoors	✅ Yes	❌ Fumes
Penetrates porous surfaces	❌ No	❌ No

⚠️ OSHA Warning: Bleach should not be your go-to for mold on porous materials. It can cause fumes and discoloration, and it doesn’t prevent mold from returning. [OSHA Guidelines]

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❌ When Not to Use Borax for Mold

Borax is great, but it’s not a magic bullet. Avoid using borax when:

• Mold is behind walls or in HVAC systems.
• Structural materials are water-damaged (like drywall or insulation).
• You have respiratory issues aggravated by mold cleanup—always wear PPE.

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📌 Final Tips from Brad Fishbein

• Keep humidity below 50% to prevent mold in the first place.
• Pair borax with HEPA vacuuming and dehumidifiers for best results.
• If the mold keeps coming back—there’s likely a hidden moisture problem.

“Borax is a great DIY mold tool—but not a replacement for fixing leaks and controlling humidity. Always address the root cause.” — Brad Fishbein, Licensed Mold Assessor

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🧠 FAQ: Borax Mold Questions

Can borax kill mold?

Yes—on hard surfaces, borax kills mold and inhibits regrowth.

Is borax made from boron?

Yes, it’s a refined form of boron-based mineral salts.

Can I use borax on walls?

Yes, as long as they’re non-porous and not water damaged.

What’s better—borax or vinegar?

Borax prevents mold from returning. Vinegar kills mold, but doesn’t leave a residue.

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🔗 Learn More About Mold Removal:

• How to Kill Black Mold

• Mold on Clothes: What to Do

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