Does Borax Kill Mold?

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.

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:

• Borax
• Water
• A 1 Gallon Container (I prefer to use this one)
• Glass Spray Bottle
• Scrub brush, old rags, or sponge

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.

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