Does Borax Kill Mold?

This post may contain affiliate links. Read our full disclosure.

When it comes to cleaning mold and mold removal, there are a lot of options available. Some work well, some don’t work at all, and some fall in-between the two extremes. Borax falls on the “works well” end of the spectrum. Let’s answer the question “does borax kill mold?”

What Is Borax?

Borax (sodium tetraborate) is a natural white mineral and salt powder compound derived from boron, a non-metal element which is mined from the ground. It is most often found in dried-up lake beds. It has a pH level of 9.3 and is very alkaline.

Borax is often used in making glass and ceramics and is found in many cleaning products.

Borax is often confused with boric acid but they are NOT the same thing.

A box of borax about to be used to kill mold

Does Borax Kill Mold?

Most, but not all types of mold prefer an environment where the pH is somewhere between 3 and 7, which is more on the acidic side (a pH of 7 is considered neutral).  Some molds even like to live in pH environments below 3. 

Remember how I said that borax is quite alkaline with a pH of 9.3?  Applying borax to mold creates an environment that is not suitable to additional mold growth. In many cases borax kills mold spores by turning up the pH levels and making their environmental inhospitable.

Borax won’t always kill mold but in many cases it will.

How To Remove Mold With Borax

You will need:

Method 1 – Borax Mold Spray

  1. Place 1 cup of borax in the gallon container.
  2. Fill the container with hot water, put the lid on, and shake it well. This helps dissolve the borax more completely and faster.
  3. Pour the solution into the spray bottle.
  4. Spray the affected area. Be careful not to use too much on a porous material, like unfinished wood or drywall.  These materials absorb water, which will feed the mold by keeping it moist.
  5. Scrub the area with a scrub brush, rag or sponge until mold is removed. 
  6. Wipe the area clean and dry the area.  You can spray a light misting of the borax mold spray again.
  7. You do not have to rinse afterwards. The borax will usually prevent the mold returning so long as you have addressed the source of the mold including any leaks or water intrusion issues.

Method 2 – Borax Mold Paste

Often called “borax paint”, this method is used to kill mold on wood, not remove mold so to speak. I don’t recommend leaving moldy wood in place and then applying a mold killing product to the wood. I prefer to remove all moldy material and start fresh. But that’s just me.

  1. In a 2+ quart saucepan, mix 1/2 cup of borax and 2 quarts of boiling water.
  2. Stir well until most of the Borax is dissolved. Some borax will settle at the bottom which is ok.
  3. Using a paintbrush or a rag, cover every bit of mold with the borax paint. It looks like cloudy water but dries white.
  4. Allow it to dry.
  5. You can paint over the wood with mold resistant paint or primer if you would like.

Does Borax Kill Mold On Clothes?

I have an entire post dedicated to how to remove mold from clothes but thought I would quickly share how borax works for that.

How to Remove Mold From Clothes With Borax

  1. Mix half a cup of borax powder with hot water. This is to make sure it completely dissolves.
  2. Add the borax and water solution to your washing machine after it has filled with water.
  3. Washing your clothes as you normally would. You can do a presoak if you would like but it is not necessary.

What About Borax and Vinegar For Mold?

You might have read something about borax and vinegar joining forces to kill mold. If so, you are probably wondering how to mix borax and vinegar to kill mold and whether or not it works.

You can read more about mold and vinegar in my post Does Vinegar Kill Mold. But in a nutshell, don’t bother with the vinegar. It doesn’t do a whole lot and there is no major benefit to combining borax and vinegar.

Some people prefer to spray vinegar on the affected area after cleaning it with borax but again, there is really no point in doing so. The borax is doing its thing just fine solo.

Pros of Using Borax To Kill Mold

  • Borax is chemical-free.
  • It does not emit dangerous gases.
  • Borax is also not as bad for the environment as bleach is.
  • Borax can be mixed with most other substances safely.
  • Borax is very cheap and easy to find.
  • It creates an inhospitable environment for mold to grow and thrive in.

Cons of Using Borax To Kill Mold

  • Borax has a low toxicity level. It is still toxic if swallowed, however. 
  • Borax can irritate sensitive skin.
  • NOT remove or kill mycotoxins. This is a major con. Be sure to read my post about mycotoxins so you have a better understanding of why you need those bad babies dead.

Cost of Borax

Borax ranges from $5.99 for a 4 ounce bag to $30 for a 1 gallon (9 lbs) container.

Where To Buy Borax

You can usually find borax at your local supermarket, big box store, or hardware store. Amazon sells it as well. This is the brand of Borax I use and trust.

Is Borax My Go-To To Kill Mold?

Not typically. Like I mentioned above, it doesn’t tackle mycotoxins and where there is mold there are mycotoxins. There is only one product that I trust completely to kill both mold spores and mycotoxins. If you are interested, you can check out my favorite product to kill mold and mycotoxins here.

You Find These Posts Helpful

An image of borax on a spoon about to be used to make borax mold remover

Leave a Reply

Your email address will not be published. Required fields are marked *

25 Comments

  1. Can you sprinkle dry borax on books to kill mold??? My bookshelf was covered in mold months ago. I took everything out and cleaned the wood with vinegar and the mold seemed to go away but now it has returned and I realized it is also on the actual books and book covers!! I have a ton of books so going through each one one by one to clean individually would take forever… Can I just sprinkle borax around and atop the books to kill the mold for now?? I have ordered a dehumidifier but it won’t be here for a week, and I plan to replace the bookcase as soon as I can but that will probably be a month or so…

      1. Hello. Due to a water line leak, we got water under our entire vinyl plank floor and the underlayment in our basement. I removed both and dried the area. After sitting in my garage for a few days, some of the waterproof vinyl planking seems to have a slight mildewy smell. I want to clean the planks before reinstallation. I have borax in the house now and was wondering if I could use it on the planks. Thank you!

  2. In the section that tells what you will need, under 1 gallon container, you say “I prefer to use this one”, when you click on “this one”, it brings up a grout brush on Amazon.

    1. Oh gosh! Thank you for letting me know! I will get that remedied.

  3. Hi, Your articles are great! Thanks for sharing all your knowledge!! I just have a quick question, you say to use a glass bottle for spraying. Does it have to be glass? You don’t recommend a glass bottle for mixing it. I’m just afraid it will be easier for me to break a glass bottle when cleaning and I prefer to use plastic for these types of things in case it gets knocked over or knocked off a surface. Is there a specific reason you call for a glass spray bottle? Thanks! Karen

    1. I prefer to use a glass spray bottle because the borax can be harsh on plastics on break them down. Having said that, if you aren’t storing unused product for a long time, plastic is ok to use.

  4. Susan G. Schwichtenberg says:

    I have a question about.changing Ermi scores to Hermi scores. Under the list of each type of points awarded, do you add points for each type listed or just if you have any?

  5. *Mixing Borax and vinegar is actually COUNTER-PRODUCTIVE. At least your information wasn’t actually anti-scientific, it’s remarkable how much much conflicting and often just wrong info there is out there about controlling mold before painting.

    So the specific issue here is that borax is a base and vinegar is acid. They cancel each other out. Do not mix, unless you want to make water.

    1. I specifically say not to bother with mixing the two. Also not sure where painting came into play. I would never advocate for “controlling mold before painting.” Mold must be removed. Period. Not controlled and then painted over.

      1. I think Viborg’s point is more than just don’t bother – the two products cancel each other. Use one or the other, but do not use both at the same time. The acid of the vinegar neutralizes the alkalinity of the borax so you take the effectiveness out of both. You end up with a neutral pH, so you are not killing mold with acidity or alkalinity.

        I want to use a borax paste to prepare wood windows, which are prone to condensation, before finishing them, to prevent mold from establishing in the wood.

  6. How would you suggest adding the borax and water solution to a front loading washer that locks once filled with water?

    1. Hi there! You can add it directly to the pre-soak container if you have one of those and the remainder into the detergent container. This usually works well. You would put it on a short wash cycle in the do another cycle laundering your items as you normally would. You can also just pour it onto the items you are washing and let it soak in for a few minutes before starting the washing machine too.

  7. Tammy Johnson says:

    How do I remove mildew/mold from popcorn ceiling in bathroom?

  8. Are you able to sprinkle dry dorax in between the laminate flooring and wood floor to dry it out/kill mold and spours?? Then go back to clean it up

    1. Hi Lori! Unfortunately this won’t exactly work. It might lesson the impact of the mold growth in terms of soaking up the moisture but if there is mold growing on the flooring it won’t remove it.

  9. Jane Burkey says:

    My name is Jane Burkey and I have a mold problem. Do you mind sending your full name and your certification number with the International Association of Certified Indoor Air Consultants, Inc. Or, maybe it’s called the International Association of Certified Mold Inspectors. I don’t know the names. I don’t even know a thing about mold, and much less the Regulator’s names. But I know there is a lot of mis-information on the internet and I just need to do my due diligence.
    Thank you,
    Jane

  10. Hey Jennifer!
    I bought a home last year and have been struggling with mold growth in my lower kitchen cabinets since! So far I’ve tried basic vinegar cleaning (we both know that didn’t work) I’ve wiped down wood with pure bleach (used gloves) and didn’t rinse, let it dry then wiped down with a dry cloth to remove any residue. Although this has inhibited a great deal I do still have return of mold growth. Do I even have a chance with borax? Would you suggest something else? Can I salvage my cast iron cookware, cutting boards or anything else that is now covered in mold? The cabinets are basic plywood construction that have been sealed within and without using a basic poly/varnish. I don’t see mold on the cabinets themselves, just anything porous that is stored in them. Help!

    1. Hi Natalie. If your have high humidity in those cabinets which is allowing for mold growth, this suggests a leak. Have you ruled that out yet? This will continue so long as there is moisture getting inside the cabinets. I would suggest you use Superstratum. https://moldhelpforyou.com/superstratum-review/ You want to use the Everyday Cleaner to remove the mold and then their Protectant to try to stop the repeating of the cycle of mold growth. Again, this will only work if there isn’t an active source of moisture. I would never advocate for trying to salve items you cook with that are covered in mold, especially wood items. Cast iron is a maybe.

  11. Suzanne Begin says:

    Hi!
    Above, you say to add borax and water solution to the washing machine “after it has filled with water.” What is your recommendation for HE machines, which never really “fill up” with water? Also, since borax doesn’t deal with mycotoxins, would it work to add a citrus seed extract to borax? The cost to ship EC3 products to Canada is ASTRONOMICAL…

      1. Suzanne Begin says:

        You’re amazing, thanks! Yes, the Agrisept product is available and it’s a good value compared to my other options, yeh! So, borax can be added at the “start” of the wash (before adding clothes), i.e. it doesn’t have to be added “mid cycle,” as was suggested elsewhere on the site?