Add 1/2 gallon of water to your bucket, stir in washing soda and borax.
Shred soap bar using a box grater.
Melt soap shreds in 1 cup of water on the stove over medium heat. Stir often until melted.
Add the melted soap to the bucket and stir in well.
Stir in essential oils.
Fill the rest of the way with water to about 3 inches from the top. Mix well with an immersion blender or large stir stick.
Secure lid, let it sit overnight, then give it a good shake before using.
Notes
An immersion blender works well to combine the ingredients if you have one.For easier handling, fill an old detergent container or 1/2 gallon mason jar with the soap and store the bucket out of the way. Use 1/4 cup per load. The essential oils are optional and can be omitted from the recipe.Always follow these safety instructions when handling borax.Scroll up for step-by-step images!The original recipe called for a Fels-Naptha bar to make this laundry soap. Since then, I've switched to a Castile soap bar. The Castile soap bar makes a runnier final product that doesn't gel up like the Fels-Naptha version. However, the cleaning performance seems to be the same.