As seen here:
http://www.thefrugalshopper.com/articles/detergent.html

Recipe #1

3 Pints Water
1/3 Bar Fels Naptha Soap, Grated
1/2 Cup Washing Soda
1/2 Cup Borax
2 Gallon Bucket
1 Quart Hot Water
Hot Water

Mix Fels Naptha soap in a saucepan with 3 pints of water, and heat on low until dissolved. Stir in Washing Soda and Borax. Stir until thickened, and remove from heat. Add 1 Quart Hot Water to 2 Gallon Bucket. Add soap mixture, and mix well. Fill bucket with hot water, and mix well. Set aside for 24 hours, or until mixture thickens. Use 1/2 cup of mixture per load.


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Recipe #2

1 Cup Grated Fels Naptha Soap
1/2 Cup Washing Soda
1/2 Cup Borax
2 Tablespoons Glycerin
2 Cups Water

Mix all three ingredients together. Add glycerin and water.
Use 1/2 - 3/4 cup per load. Best when used with cold or warm water.


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Recipe #3

Water
1 Bar Fels Naptha Soap, Grated
5 Gallon Bucket
1 Cup Washing Soda
4 1/2 Gallons Hot Water

Place grated soap in a small saucepan and cover with water. Heat on low until dissolved. Fill bucket with hot water, and add soap. Stir to combine. Add 1 cup washing soda and mix well. As it cools it will thicken. May be used immediately. Use 1-2 cups per load.


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Powdered Laundry Detergent


1 Cup Grated Fels Naptha Soap
1/2 Cup Washing Soda
1/2 Cup Borax

For light load, use 1 tablespoon. For heavy or heavily soiled load, use 2 tablespoons.