Here's the recipe:
1 Fels Naptha soap bar, grated
1 cups washing soda
1/2 cup borax
Leftover liquid detergent container
Grate the soap bar into a small saucepan (I used my food processor, but a hand grater would work fine.).
Cover with hot water. Cook over medium-low heat, stirring continually, until the soap completely dissolves.
Put washing soda and borax in a 5-gallon bucket. Pour in the hot, melted soap mix. Stir well, until all the powder is dissolved. Fill the bucket to the top with more hot tap water. Stire, cover securely and let set overnight. The next morning, stir. Mix equal amounts of soap concentrate and water in a smaller detergent container. Shake.
For top-loading machines: Use 1 cup of the soap mixture per load
For front-loading machines: Use 1/3 cup per load
You can find the ingredients in the laundry detergent aisle at the grocery store. The Fels Naptha is usually in the same place as the other stain removers. I use Arm & Hammor Washing Soda and Mule Team Borax. Each of these boxes cost less than $5 and will make at least four batches of detergent. It all adds up to detergent that costs less than $5 per batch and lasts this family around 4 months. Can't beat that!
Note: This detergent is missing a lot of the chemicals and stabilizers the commercial detergent has. The consistency is somewhat like pieces of jello sitting in water. Don't worry about it. Just give your container a shake before your pour.
I've got to make some more this afternoon. I'll post pictures for you so you can see how it goes together.