Most of the DIY homemade laundry soap recipes you'll see use Fels Naptha Soap, a real soap that's been around for 100 years and is specially designed for the laundry.
If you don't want to use a commercial soap as the base for your laundry soap, you can substitute any bar of soap, though we do recommend one that's not got a lot of extra oil (superfatted). Many folks use a 100% lard soap with 0% superfat. You want a good, super-cleansing bar. (Extra oil is good for your skin, but not for your clothes.) If you don't mind that it's not a "natural" soap, the Fels Naptha Soap works great.
- 1 bar of fels naptha (or other) soap with a low superfat
- 1 cup of borax
- 1 cup of washing soda
- 1 gallon plus 1 quart of water
- First, using a food processor or manual grater, finely grate the bar of soap.
- Bring a quart of water to a boil on the stove and slowly add the soap, stirring gently.
- Reduce the heat and let it simmer gently until all of the pieces of soap are melted/dissolved.
- Add the borax and washing soda and stir until they are dissolved.
- In a separate pot, heat up a gallon of water or measure out a gallon of very hot tap water.
- Pour the soap/borax/soda mixture into a large container and slowly add the gallon of water to it.
- Stir until the mixture is well mixed.
- Let it sit overnight. It will "gel" together...kind of a custard-like consistency. We've also heard it described as "thick egg drop soup."
- Stir or shake the soap each time you use it.
- Use 1/4 cup for a front loading washer. Use 1/2 cup for a top loading washer.
Many people who use homemade soap in their washers also recommend using 1/4 cup of white vinegar in the place of the fabric softener. This not only helps soften your clothes but helps clean out any residual soap scum from your clothes and washer.
Note: Some people have reported having trouble finding washing soda (sodium carbonate) in their city. You can leave it out of the recipe, but it does help boost the cleaning power of the soap. Good news though, there is a way to make your washing soda out of regular baking soda (sodium bicarbonate).