I've been making my own laundry soap for a couple of years now and I love it. It's practically free - I spend maybe $3 per batch, (10 gallons) which lasts me around 3-4 months. It's a little messy and time consuming, but well worth the pay off. It cleans every bit as well as any brand name soap. The recipe is not original. I found mine in the Duggar's book "20 and Counting". Here's how we make it...
Gather your materials - one bar of Fels-Naptha soap. You will find this in most grocery store laundry isles. Some Walmart stores have it and others don't. I have found it most often at the grocery store. You will have to look carefully - it's small and they usually put it on the very top shelf. It costs around $1.35 per bar.
You will also need 20 Mule Team Borax. You only use 1/2 cup of this per batch, so it will last you a long time.
The last ingredient is washing soda. This and the borax are also found in the laundry isle. You will need one cup of the washing soda per batch.
Other things you will need are a grater, a long handled spoon or spatula (I use a cheap barbecue hamburger flipper), a medium sized pot that does NOT have a teflon coating - glass or ceramic is ideal. Melting the soap will remove all the teflon from your pan and make a huge mess ... trust me, I know. Then you will need a 5 gallon bucket with a lid, and a smaller old laundry detergent container with a lid. I'll explain all this as we come to it.
Step one is to grate the Fels Naptha. Use the smallest holes on the grater. It will help the soap dissolve easier.
This is the worst part, so I usually bribe someone else to do it ;) You need to get all the chunks the same size - as small as possible. It's tempting to just throw in the remaining scrap of soap, but it won't dissolve ... ever ... so don't bother.
See how fine we have grated this?
It's like a fine powder similar to cornmeal when you're done.
Add water, then place on low-medium heat. You want this to warm SLOWLY. If it boils, you will have bubbles all over the place and your soap will not be melted. Take your time, but make sure you stir it often. It will be goopy, and clumpy until it really starts dissolving. Be patient.
Add more water as needed. You want to leave room in your pot for expanding though. It's better to use a larger pot because more water makes the next step easier, but when this is almost done, it starts bubbling up and can boil over pretty easily if you're not careful.
Continue stirring throughout the dissolving process.
While you wait for the Fels-Naptha to dissolve, get out your clean, dry bucket and put 1 cup of washing soda and 1/2 cup Borax in it. Break up any clumps.
When the Fels-Naptha is all dissolved, pour it into the bucket with the dry ingredients.
Stir until the dry ingredients are dissolved. It is very important to do it this way. I tried once to dissolve the dry ingredients with water, and it didn't work. The end result was not good and I had a lot of waste.
Once it's all dissolved, you're ready to add water.
Gently add very hot tap water to your bucket until you have 5 gallons. Look on the side of your bucket - most of them are larger than 5 gallon quantity so you will have extra room for stirring.
Once you've added all your water and mixed everything together, scrape the foam off the top of your soap.
Can you see the little yellow chunks floating by the edge of the bucket? This is why you need to scrape the foam off. These are undissolved bits of Fels-Naptha, and they will never dissolve, so you don't want them in your wash or you'll end up with chunks on your clothes. It won't hurt anything, but you'll have to wash them over again, and who wants to do that? So just scrape them off now.
This is what the soap looks like when you're done. Well, actually, you're not done :)
Put your lid on the bucket and let it sit overnight. Then read part two to see how you're supposed to use this. There is some very important information in part two, so don't skip it.