1 bar of soap (you can use any bar soap you want, but I prefer Fels Naptha)
1 cup of washing soda (you need actual washing soda, not baking soda)
1/2 cup of Borax (this isn't necessary, but I find it adds that little extra oomph)
4 cups plus approximately 4 gallons of water
Container(s) of some sort, either a 5-gallon bucket or 4 milk jugs (I've used an old, clean cat litter bucket, and I've used old, clean milk jugs. I prefer the milk jugs. Costco jugs are the best because they're slightly larger in volume than a gallon.)
essential oils (optional, but they give the soap a nice smell. Use about 10-12 drops per every two gallons.)
1. Grate soap (I use a cheese grater I bought specifically for soap making) and add to 4 cups of hot water. "Cook" over medium heat until soap is completely melted. Remove from heat.
2. Add washing soda and Borax and stir until completely dissolved.
3. If using a bucket, pour mixture into the bottom of the bucket and add 4 gallons of warm water. Stir to mix. Add oil if you want. If using milk jugs, divide mixture evenly among the 4 jugs (so, about a cup per jug). Fill jugs with warm water (no need to measure). You may need to fill them several times as the soap will foam up. Fill almost to the top, but make sure you leave enough room to be able to shake the contents. Add oil if you want (5-6 drops per jug). Shake.
4. Let soap sit 24 hours. When ready to use, mix/shake thoroughly. It will probably be lumpy and slimy, but that's normal.
5. When ready to use, pour soap in washing machine before adding clothes. It works best this way.
I use 1/2 cup of homemade soap per load. I also throw in some Oxy Clean for a little extra boost. When I remember, I pour half a cup of distilled white vinegar into the rinse cycle instead of using dryer sheets. If I forget, I still don't use dryer sheets.
This recipe will last me about 3 months, so it's very cost-efficient!
One extra note:
If you're going to make your own laundry soap and wait until you're completely out before making more, don't enjoy your laundry-free 24 hours too much. Because if you do, you'll be paying for it when those 24 hours are up. Believe me. I had to wash 5 loads of laundry yesterday to make up for not doing any on Tuesday. And today, I have another 3. All because I waited until I was completely out. Oh, well. I sure enjoyed Tuesday!