How To Remove Mold & Mildew Stains With Borax?

Updated on 17-Feb-2025

Discovering Mold Stains: A Common Household Problem

Mold stains are a frequent issue in homes, appearing on walls, vinyl, wood, and other surfaces due to moisture buildup. These stains are not only unsightly but can also indicate deeper mold growth that could pose health risks. Homeowners often seek effective and safe solutions to remove mold stains and prevent regrowth.

Will Borax Remove Mold Stains, Is It Good for Mold Removal?

Borax has gained attention as a natural cleaning agent with antifungal properties, but does it truly work on mold stains?

Many DIY cleaning methods suggest using borax to kill mold spores and lighten discoloration, but its effectiveness depends on the type of mold, surface material, and application process.

This article will provide a detailed examination of borax as a mold stain remover, covering:

• Borax’s properties and how it interacts with mold.
• Whether borax kills mold spores or just removes stains.
• Step-by-step instructions on using borax for mold removal.
• Comparison with other cleaning agents like vinegar, baking soda, and bleach.
• When to consider professional mold remediation.

By the end, you’ll have a clear understanding of borax’s role in mold stain removal and whether it’s the right solution for your cleaning needs.

Key Takeaways on Using Borax for Mold Stain Removal

• Borax is effective for killing mold and preventing regrowth, thanks to its antifungal and alkaline properties.
• Borax can help remove mold stains, but its effectiveness varies by surface type. It works well on vinyl, tile, and non-porous materials, but may not fully remove deep-set stains on porous surfaces like drywall or unsealed wood.
• Proper application is crucial—mixing borax with water, allowing dwell time, scrubbing, and thorough drying improves results.
• Safety precautions should be followed, including wearing gloves, a mask, ensuring proper ventilation, and avoiding ingestion.
• Borax vs. other cleaning agents: It outperforms vinegar and baking soda in mold prevention but is less effective than bleach for quick stain removal. However, bleach does not prevent mold regrowth.
• For extensive mold growth, professional mold removal is recommended, especially if mold covers a large area, returns frequently, or causes health symptoms.

Borax is a safe, affordable, and eco-friendly mold treatment for mild to moderate mold stains. When used correctly, it helps maintain a mold-free home, but for severe cases, professional remediation may be necessary.

What is Borax?

Understanding Borax: A Versatile Cleaning Agent

Borax, chemically known as sodium borate or sodium tetraborate decahydrate, is a naturally occurring mineral composed of boron, sodium, oxygen, and water. It has been widely used as a household cleaner, disinfectant, and mold inhibitor due to its alkaline properties.

Key Properties of Borax

• Alkaline Nature: Borax has a pH of around 9.3, making it effective at breaking down organic substances, including mold.
• Antifungal & Antibacterial: It inhibits the growth of fungi, mold, and bacteria by disrupting their cellular processes.
• Non-Toxic to Surfaces: Unlike bleach, borax does not produce harsh fumes or damage most non-porous surfaces.
• Water-Soluble: Easily dissolves in water, forming a cleaning solution suitable for scrubbing and stain removal.

Common Uses of Borax

Beyond mold removal, borax is commonly used in:

• Laundry Detergents: Helps remove stains, odors, and hard water buildup.
• General Cleaning: Acts as a degreaser and deodorizer for household surfaces.
• Pest Control: Used to repel ants, cockroaches, and other insects.
• Water Softening: Neutralizes hard water minerals that interfere with soap lathering.

Safety Considerations When Using Borax

Although borax is a natural compound, it should be handled with care:
✔ Avoid Ingestion: Borax is toxic when swallowed and should be kept away from children and pets.
✔ Wear Gloves: Prolonged skin contact can cause mild irritation.
✔ Ensure Ventilation: While borax doesn’t produce strong fumes, proper airflow reduces dust inhalation risks.
✔ Store Properly: Keep borax in a sealed container to prevent moisture absorption and clumping.

Understanding borax’s properties and safe usage is crucial before using it to remove mold stains effectively.

Does Borax Kill Mold?

Borax as a Fungicidal Agent

Borax is widely recognized for its antifungal and antibacterial properties, making it a popular choice for mold treatment. Unlike bleach, which only removes surface mold, borax penetrates deeper, disrupting mold spores at the cellular level and preventing future growth.

How Borax Kills Mold Spores

Borax works by:

• ✔ Altering pH Levels – Mold thrives in slightly acidic to neutral environments. Borax’s high pH (9.3) makes it difficult for mold to survive.
• ✔ Dehydrating Mold Cells – As an alkaline mineral, borax absorbs moisture, creating an environment where mold struggles to regrow.
• ✔ Preventing Spore Reproduction – Unlike some cleaning agents that remove visible mold but leave spores intact, borax interferes with mold’s reproductive process, reducing the chances of regrowth.

Effectiveness of Borax on Different Mold Types

• Black Mold (Stachybotrys chartarum): Borax can help inhibit growth, but extensive black mold infestations often require professional remediation.
• Mildew & Surface Mold: Works effectively on non-porous surfaces like vinyl, tile, and sealed wood.
• Embedded Mold: Borax is less effective on porous surfaces like untreated wood and drywall, where mold may have penetrated deeper.

Limitations of Using Borax for Mold Removal

• ⚠ Does Not Remove Deeply Embedded Mold – If mold has penetrated drywall, insulation, or porous wood, the affected material may need to be removed and replaced.
• ⚠ Requires Physical Scrubbing – Borax does not instantly dissolve mold; scrubbing is needed to remove stains and residue.
• ⚠ Not a Quick Fix for Large Infestations – Severe mold issues may require professional assessment, especially if they cover more than 10 square feet.

Borax is an effective solution for small-to-moderate mold problems but may not be sufficient for deep-rooted infestations.

Borax For Mold Stains Removal

How Borax Works on Mold Stains

Borax is effective at killing mold spores, but its ability to remove stains depends on several factors, including the type of surface and the severity of discoloration.

Borax works by:

• Lifting organic residue by breaking down mold stains.
• Lightening discolored areas over time, though it is not a bleaching agent.
• Preventing future stains by inhibiting mold regrowth.

Effectiveness on Different Surfaces

Borax performs differently depending on the porosity and material of the surface:

What to Expect from Borax for Mold Stain Removal

• Light surface stains can be removed with scrubbing and repeated applications.
• Moderate discoloration may require multiple treatments for noticeable improvement.
• Deep-set stains may not be fully removed, especially in porous materials like drywall or raw wood.

For stubborn stains, combining borax with baking soda or hydrogen peroxide can improve results. However, in cases where mold stains are permanent, repainting or material replacement may be the only solution. Borax is a powerful mold inhibitor, but its ability to completely erase mold stains depends on the severity of the staining and the type of material affected.

How to Use Borax to Remove Mold Stains (Step-by-Step)

Using borax to remove mold stains requires proper preparation, application, and post-cleaning care to ensure effective results. Follow this structured approach for the best outcome.

Step 1: Gather Supplies

Before starting, collect the necessary tools and materials:

• Borax powder
• Warm water
• Spray bottle or bucket
• Soft-bristled brush or sponge
• Microfiber cloths
• Protective gloves
• Face mask
• Safety goggles
• Fan or dehumidifier (for drying)

Step 2: Prepare the Borax Cleaning Solution

The effectiveness of borax depends on the correct dilution. Use the following method to mix the solution:

• Mix one cup of borax with one gallon of warm water in a bucket.
• Stir until the borax is fully dissolved.
• Pour the solution into a spray bottle for easy application on vertical surfaces.

Step 3: Apply the Borax Solution

• Spray or apply the borax solution generously to the mold-stained areas.
• Allow it to sit for 15 to 30 minutes to penetrate and break down the mold stains.
• For porous surfaces like wood, let the solution soak in longer to reach deeper mold spores.

Step 4: Scrub the Mold Stains

• Use a soft-bristled brush or sponge to scrub the area gently.
• Apply extra pressure on stubborn stains but avoid excessive force that could damage the surface.
• If dealing with tile or grout, use a toothbrush or grout brush for targeted cleaning.

Step 5: Wipe and Rinse (If Necessary)

• In most cases, borax does not need to be rinsed off since it acts as a mold inhibitor.
• If residue buildup occurs, wipe the area with a damp microfiber cloth to remove excess borax.
• For surfaces like vinyl, a quick rinse with clean water may be necessary.

Step 6: Dry the Area Thoroughly

• Use a dry microfiber cloth to remove moisture.
• Increase airflow by using a fan, dehumidifier, or open windows to prevent mold from returning.
• For bathrooms and kitchens, keep ventilation running to maintain low humidity levels.

Step 7: Monitor for Mold Regrowth

• Inspect the treated area after a few days to ensure stains do not return.
• If discoloration persists, repeat the cleaning process or consider an additional treatment with baking soda or hydrogen peroxide for stronger stain removal.

Following these steps ensures effective mold stain removal while preventing regrowth. Proper drying and ventilation are key to maintaining a mold-free environment.

Safety Precautions When Using Borax

While borax is a natural and effective cleaning agent, it requires proper handling to ensure safety during use. Follow these precautions to minimize risks and protect yourself from potential exposure.

1. Wear Protective Gear

Borax is generally safe but can cause irritation if it comes into direct contact with skin or eyes. Use the following protective equipment:

• Gloves: Wear rubber or nitrile gloves to prevent skin irritation.
• Face Mask: Use an N95 or similar mask to avoid inhaling borax dust or mold spores.
• Safety Goggles: Protects eyes from accidental splashes during cleaning.

2. Ensure Proper Ventilation

• Open windows and doors to maintain airflow, especially when using borax in enclosed areas.
• If cleaning in a bathroom or kitchen, turn on exhaust fans to reduce airborne particles.
• Avoid prolonged exposure to borax dust by working in well-ventilated spaces.

3. Prevent Skin and Eye Contact

• If borax comes into contact with skin, wash the area immediately with soap and water.
• In case of eye exposure, rinse with clean water for at least 15 minutes and seek medical attention if irritation persists.

4. Avoid Ingestion and Food Contamination

• Borax is toxic if swallowed. Keep it out of reach of children and pets.
• Do not store borax near food or cooking surfaces.
• If accidental ingestion occurs, drink water and contact poison control immediately.

5. Store Borax Safely

• Keep borax in a sealed, dry container to prevent moisture absorption.
• Store it in a cool, dry place away from direct sunlight.
• Label containers clearly to avoid confusion with other household products.

6. Dispose of Borax Properly

• Dispose of unused borax or excess solution by flushing it down the drain with plenty of water.
• Do not dump large amounts directly into soil or natural water sources, as borax can be harmful to plants and aquatic life.

By following these precautions, borax can be used safely and effectively for mold removal without posing unnecessary health risks.

Borax vs. Other Mold Removal Methods

While borax is a reliable option for mold stain removal, other cleaning agents are commonly used for similar purposes. Comparing their effectiveness, safety, and application can help determine the best method for your situation.

1. Borax vs. Vinegar

Verdict: Vinegar is an effective mold killer but does not prevent future growth as well as borax. Borax is better for long-term mold prevention.

2. Borax vs. Baking Soda

Verdict: Both options work well, but borax is stronger for mold prevention, while baking soda is ideal for moisture control and light cleaning.

3. Borax vs. Bleach

Verdict: Bleach is more effective for removing visible stains but does not address deep-rooted mold. Borax provides a longer-lasting solution by preventing mold regrowth.

4. Borax vs. Commercial Mold Removers

Verdict: Commercial mold removers are convenient for quick results, while borax is a safer, long-term mold prevention solution.

Which Method is Best?

• For light mold stains: Vinegar or baking soda can be effective.
• For deeper mold stains and prevention: Borax is a strong option.
• For quick stain removal: Bleach works well but does not prevent regrowth.
• For severe mold infestations: A commercial mold remover or professional service may be required.

Each method has its strengths, and the best choice depends on the surface type, severity of mold growth, and long-term prevention needs.

When to Call a Mold Removal Professional ?

While borax and other DIY mold removal methods can be effective for small mold stains, there are situations where professional intervention is necessary. Mold infestations that extend beyond the surface can pose serious health risks and structural damage, requiring specialized treatment.

1. Signs You Need Professional Mold Removal

Extensive Mold Growth

• If mold covers more than 10 square feet, it indicates a deeper infestation that DIY solutions may not fully remove.
• Mold spreading across multiple surfaces or into walls, ceilings, or flooring suggests a hidden moisture problem.

Persistent Mold Regrowth

• If mold returns despite multiple cleaning attempts, the root cause may not be fully addressed.
• Recurring mold often signals ongoing moisture issues, such as hidden leaks or improper ventilation.

Musty Odors Without Visible Mold

• A persistent moldy or musty smell may indicate hidden mold growth behind walls, insulation, or flooring.
• If mold is growing out of sight, professional testing and inspection are needed.

Water Damage or Leaks

• Leaky pipes, roof damage, or flooding can create ideal conditions for mold growth.
• If mold appears after water damage, professional remediation is often required to prevent further spread.

Mold Toxicity – Health Symptoms Related to Mold Exposure

• People sensitive to mold may experience allergic reactions, respiratory issues, or skin irritation.
• If household members develop chronic coughing, sneezing, headaches, or asthma flare-ups, mold exposure could be a contributing factor.

2. Benefits of Hiring a Professional Mold Removal Service

Advanced Mold Detection & Testing

• Professionals use moisture meters, infrared cameras, and air quality tests to detect mold growth beyond visible surfaces.

Safe & Effective Removal

• Experts use EPA-approved mold remediation techniques to remove mold at its source.
• Specialized treatments prevent cross-contamination, ensuring mold does not spread to unaffected areas.

Moisture Source Identification

• Addressing the underlying cause of mold, such as leaky pipes, poor ventilation, or high humidity, is crucial for long-term prevention.

Prevention & Warranty

• Many mold removal services offer warranties or long-term prevention solutions, providing peace of mind.

Professional mold removal in Toronto, may cost more than DIY solutions, but it ensures thorough treatment, long-term prevention, and a healthier indoor environment.

Here are some references that support the use of borax for mold removal:

• Borax as a Disinfectant for Citrus Fruit – This study examined the effectiveness of borax in controlling mold on citrus fruits, showing better results against blue mold compared to green mold. Read here.

• The Borax Treatment of Citrus Fruits for Prevention of Decay – This study found borax to be highly effective in protecting against blue mold infections on citrus fruits. Access PDF.

• Reducing Decay in Citrus Fruits with Borax – Investigated how heated borax solutions reduce blue mold and stem-end rot on citrus fruits. Read PDF.

• Risk for Mould Growth in Insulation Materials – Found that borax, in combination with other compounds, helps prevent mold growth in cellulose insulation. Read PDF.

• Improvements in Fire Resistance, Decay Resistance, and Anti-Mold Properties in Plywood Treated with Borax – This study discusses how borax improves decay resistance and inhibits mold growth. Read PDF.

• Study of Natural Extracts as Replacers of Borax in the Treatment of Rubber Wood – Compared borax treatments with natural extracts to assess their effectiveness in preventing mold growth. Read PDF.

• Adsorption of Sap Stain and Mold-Control Chemicals by Wood – Explores the effectiveness of different borax formulations in mold control on wood surfaces. Read here.

• Reducing Leaching of Boron-Based Wood Preservatives – Reviews research on how borax-based preservatives prevent mold growth on treated wood. Read PDF.

• Reduction of Borax/Agar-Based Gel Residues for Conservation Applications – Discusses how borax gels can be effective in mold prevention on historical documents. Read PDF.

References

•  https://www.uwyo.edu/entomology/inscts-pests/structural/mold/mold-mgmt.html
  
• https://pmc.ncbi.nlm.nih.gov/articles/PMC3488367/
• https://www.mdpi.com/2079-6412/13/4/687
• https://www.researchgate.net/publication/291794956_Mold_performance_of_some_construction_products_with_and_without_borates
• https://pubmed.ncbi.nlm.nih.gov/15238314/
• http://npic.orst.edu/factsheets/boricgen.pdf
• https://www.nature.com/articles/s41598-024-58172-x
• https://www.sciencedirect.com/science/article/pii/S2773139124000375
• https://permies.com/t/6649/permaculture-home-care-cleaning/clean-mold-mildew-organically
•  https://en.wikipedia.org/wiki/Borax