A long time ago I briefly looked into making my own laundry soap. I didn't research thoroughly, and assumed that it would not save very much money based on the ingredients. Then one of my friends explained that the ingredients make a liquid soap, which lasts far longer than I was assuming it lasted, taking the cost of laundry soap from 12 to 15 cents per load down to 1 to 2 cents per load.
I was convinced to try it.
My friend sent me this recipe (we altered it a little)
1 bar Fels Napa soap
1 C 20 Mule Team Borax
1 C Arm and Hammer Super Washing Soda
Grate soap in a food processor or cheese grater as small as you can. (If you don’t, it won’t dissolve. She has a cuisinart that worked spectacularly.)
In a large stock pot, heat 1 gallon of water and add the soap granules. Heat until all the soap is dissolved, but do not let it boil.
When the soap is dissolved, add the Borax and washing soda and dissolve these in the water.
Dump this liquid into a 5 gallon bucket and add 3 more gallons of water. Stir.
She and I both use the Kirkland brand laundry soap rectangular bucket with the lid, which fits almost exactly the four gallons.
Add 1/2 cup of this liquid to the washing machine for an extra large batch of laundry.
I am now into my second batch, and I plan to continue using this stuff. After about a month using it, I started to miss the perfume from normal laundry soap. This soap gets laundry clean, but doesn't scent it. So I bought another box of Gain (my favorite) and now include a couple of teaspoons in each load.
I am still tallying the number of loads per box of Gain I get to see what this does to the cost, but that tiny bit of the perfumed stuff makes it so I can tell if something is freshly laundered or not.
One thing I like about this homemade soap method is that the items I hang to dry are far less stiff from the detergent than they were before.