How to Make a Boric Acid Spray

Written by nicole fotheringham | 13/05/2017
How to Make a Boric Acid Spray
Use household items to create a spray to kill cockroaches. (Hemera Technologies/ Images)

Boric acid is a helpful household chemical with a myriad of uses. Mixed with water and other ingredients, boric acid exterminates many insects, removes mould and kills unwanted weeds. Boric acid comes in a crystallised powder form and can be obtained from pharmacies or hardware stores. It has been classified as a poison by the EPA, and should be handled with care.

Use boric acid to remove mould on household surfaces. Don protective clothing including a respirator, gloves and eye protection. Mix together 3 parts water, 1 part 35 per cent hydrogen peroxide and 1 cup boric acid for each 1½ gallon of mixture. Substitute one part water with white vinegar to increase the longevity of your mould remediation. Mix the solution and place in a spray bottle. Apply to the mouldy surface and allow to set for 15 minutes. Scrub with a brush and allow to dry. Spray the surface with a thin film of boric acid solution to prevent the regrowth of mould.

Make your own cockroach and insect killer. This boric acid spray works on most household insects. Mix boric acid and water in a 1 to 10 ratio. Heating the water will assist in dissolving the boric acid crystals. Spray the solution on surfaces frequented by cockroaches and other pests. Be sure to avoid surfaces that might be accessible to children or pets. Boric acid will stick to the insects and slowly poison them. They will also carry it back to their nests. If you are trying to kill ants, combine a small amount of sugar with 1 cup water, 2 cups sugar and 2 tsp boric acid powder.

Remove unwanted creeping charlie from your garden with a boric acid spray. Boric acid is toxic to humans and animals, so take precautions when spraying and avoid spraying in large quantities, since the boron will remain in the soil for long periods of time. Mix 295ml. of boric acid in 118ml. (½ cup) of warm water. Pour this solution into 2 ½ gallons of cold water and mix. This is sufficient for 1,000 square feet. Use a sprayer to distribute the solution evenly. The boric acid solution works best when applied to the plants in the spring. Pick a time when rain is not forecast, and give the solution at least 48 hours to work.


Boric acid is classified as a poison by the EPA. As such, it should be kept away from children and pets.

Tips and warnings

  • Boric acid is classified as a poison by the EPA. As such, it should be kept away from children and pets.

Things you need

  • Gloves
  • Respirator
  • Eye protection
  • 35 per cent hydrogen peroxide
  • White vinegar (optional)
  • Powdered boric acid
  • Scrubber
  • Sugar
  • Sprayer

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