How to Use Boric Acid to Kill Mold

Updated February 21, 2017

Boric acid is a naturally occurring chemical with uses dating back to 900 A.D. when the Chinese used this compound to enhance the glaze on ceramic pieces. In modern times, boric acid is found in cosmetics, nutritional supplements and flame retardants as well as in pest control products, according to the National Cotton Batting Institute. If you have a mould problem, utilising boric acid in conjunction with other household items may help kill and remove this pesky, and sometimes toxic, dilemma.

Place latex gloves over your hands and gather a 2-gallon mixing bowl that comes with an airtight lid.

Add 1 cup of boric acid, 1/2 gallon of white vinegar and 1/2 gallon of hydrogen peroxide into the mixing bowl.

Mix with a wooden spoon for one minute.

Pour this mixture into a spray bottle. Use a cup to carefully pour the mould killing solution into the bottle. Place the lid on the mixing bowl to prevent the solution from losing its potency.

Put on protective eyewear and liberally spray the solution directly on the mould. Wait five minutes before applying a second coat. Boric acid is toxic to fungus species, such as mould, and works to not only kill current mould, but also reduce the likelihood of mould returning, according to Weirton Construction.

Clean the mould-killing solution after it has dried for 30 minutes. Rinse the area by dipping a kitchen sponge into cool water and scrubbing in a circular manner. Dry with a cloth or beach towel. Make sure you thoroughly dry the area, as moisture is the leading cause of mould growth.


Keep the solution tightly covered in the spray bottle, as hydrogen peroxide turns to water if excess oxygen is present.


Be careful to not spray this solution on fabrics, unless mould is present, as the hydrogen peroxide can bleach dark fabrics.

Things You'll Need

  • Latex gloves
  • 2-gallon bowl
  • White vinegar
  • Hydrogen peroxide
  • Wooden spoon
  • Spray bottle
  • Cup
  • Protective eyewear
  • Kitchen sponge
  • Towel
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About the Author

Jonathan McLelland has been a professional writer since 2005. He has worked as a story writer and editor for the international sitcom, “Completing Kaden,” as well as a proposal writer for various production companies. McLelland studied communication and theater at St. Louis Community College.