This is a super easy recipe that makes about 3 1/2 gallons of laundry detergent ... which then gives me enough for about 50 loads of laundry ... for mere pennies! I mean, it literally costs me pennies to make vs. paying $19.99 for the ginormous (but enormously popular) "Wave" brand. Yes, I miss the scent that goes with fresh laundry but that can be easily remedied by adding a fabric softener or some essential oils on a woolen dryer ball in the dryer (or did "DRYER BALL" give that away?).
1 bar laundry soap - I use Fels-Naptha
Borax powder - I use 20 Mule Team brand
Washing Soda (not baking soda ... because we're WASHING, not BAKING) - Arm and Hammer, all the way
a crockpot (enough to hold 8 cups)
a 5 gallon bucket with lid (can get at Home Depot or Lowe's but we got ours from a local restaurant that was selling them for $1/each to raise funds for an orphanage.)
Unwrap the bar of soap and put in crockpot with 8 cups of water.
'Cook' on low heat for approximately 8 hours -- about how long it takes to melt the soap. Stir the soap soup occasionally to help the soap melt quicker.
Once all melted, add 1 cup Borax and 1 cup Washing Soda to the 5 gallon bucket. Add the 8 cups of soap soup (careful, it's still hot!) and then 3 gallons of warm water. Stir it all up really well to dissolve the Borax and Washing Soda.
Put lid on the bucket and set aside overnight.
In the morning, the detergent will have gelled and you will likely wonder how on earth it will work with your laundry. Stir it up really well again, breaking up as much of the gelled pieces as well as you can. We use a funnel and an old "Wave" container to store our detergent in next to the washer. Any container is fine but you'll have to shake it up or stir the detergent a little before using. Use 1 cup per load.
Now, I still pre-treat stains, if needed. And will add Oxy-Clean or white distilled vinegar to uber-stinky loads.
We keep an eye open for when these items go on sale and then stock up -- a box of each of the Borax and Washing Soda will last for about 5 batches of soap and the Fels-Naptha can be found on sale for about $1/bar at various places throughout the year. Our go-to places are Rural King and Kroger but sometimes even Big Lots will have it.