I did search and this is what I came up with? It looks like the most recent post of homemade laundry soap.

https://www.gardenweb.com/discussions/4749533/homemade-laundry-soap#n=13

If this isn't it, maybe she'll check in and post it for you. Or someone else, for her 😉

I see Amazon sells these ingredients as a kit! I’m not sure I’d be up for this BUT that Fels Naptha has caught my eye. Looks like it might be my best laundry friend I haven't met yet! Ordering some.

Thanks Jasdip. I have forgotten how much you use per load. My sister asked me for the recipe. I have not made any in a long time.

Sue

I think it's 1/4 cup for front load. I just fill the cap on my laundry jug in the top loader.

Why do it this way?

My ex-roommate used to do it because it was cheaper.

In its most simplistic sense the thing that makes a detergent is dispersants. Soap doesnt have dispersants. When fats are saponified as in made into soap by combining fats with strong bases like lye to make soap, the soap in water will attach to dirts of various kinds. That mix of soap and dirt is soap scum. It is gunky and makes the ring in a tub. To turn soap into a detergent you add additional chemicals that are hydrophilic-attracted to water- so simplistically one end grabs the dirt and the other end grabs a water molecule and floats about(dispersed) not creating scum. The water goes gray and rinses away easily. Trying to recreate that yourself with home made mixtures of soaps like Fels Naptha which is soap with additives with things like borax and washing soda so forth is fine I suppose but sort of not very efficient. If it works for you fine. Modern laundry soap is more than that but if you don't need more go for simple.

I don't understand the benefit of spending time going through the fabrication steps described above to get a result which, at best, may be the same as what can be purchased or more likely at worst, isn't as good. Fels naphtha is an old product - the chemists at P+G and others certainly are aware of its contents as wells as newer and additional/more effective ingredients to produce best results.

I'm happy to leave it to modern experts. Laundry detergent isn't that expensive.

I could see forgoing perfumes and all the color brighteners and other weird additives. I go with simple where I can find it. I am allergic.

NON Food (weebly.com) There are a pile of recipes at the KT Gathering place.