How to Apply Antifreeze to Dry Rot

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Things You'll Need

  • 30 oz. antifreeze with propylene glycol

  • 5.6 oz. of borax powder

  • 4.4 oz. of boric acid

  • Small saucepan

  • Candy thermometer

  • Hand sprayer

Antifreeze brands that are described as environmentally or earth friendly usually contain propylene glycol.

Antifreeze, boric powder and boric acid can be effectively used to eradicate and prevent rot in wood. Boric acid and glycol are both toxic to a wide range of fungi, organisms and insects that perpetuate rot in wood. Antifreeze can have two active ingredients: either ethylene glycol or propylene glycol. Since ethylene glycol can cause damage to the heart, nervous system and kidneys through prolonged exposure, you should consider propylene glycol your only option.


Step 1

Make a concentrated solution to combat wood rot. Combine the boric acid, borax powder and antifreeze in the following ratio: 50 percent antifreeze, 28 percent borax powder and 22 percent boric acid. If you intend to make 40 oz. of concentrate, you will need 30 oz. antifreeze, 5.6 oz. of borax powder and 4.4 oz. of boric acid.


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Step 2

Place the ingredients into a small saucepan and bring them to the boil. The purpose of this is to reduce the water content. Continue to heat the mixture until it reaches 260 degrees Fahrenheit. You can use the candy thermometer to ascertain the temperature. Avoid touching the bottom of the saucepan when getting a temperature reading. Once a temperature of 260 degrees Fahrenheit has been reached, remove the mixture form the heat source.


Step 3

Combine equal parts of the antifreeze mixture with water when applying it to rotting wood. Use a hand sprayer to soak the wood surface with the mixture. Remove any sealant or finish on the wood prior to application in order to expedite penetration. Apply two coats of the antifreeze mixture for large areas of wood rot. Allow the wood to dry for two hours between applications.


Boric acid and propylene glycol penetrate wood well due to their water-solubility. However, this excludes them from use on wood that is below the water line. The antifreeze mixture should be applied only when rain or snow is not forecast. Cover with a tarp in inclement weather.


Propylene glycol is toxic to pets and children and due caution should be practiced when using and storing antifreeze. Boric acid is also very toxic, and should be stored away from pets and children although its bitter taste lessens the probability of ingestion. The antifreeze mixture is toxic to plants. Cover vegetation in the area before applying the mixture.



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