I've made my own laundry soap before, but did the liquid variety where you grate the soap and melt it in hot water on the stove, add the other stuff and it looks like egg drop soap when you are finished. It worked pretty well, but the process was labour intensive and didn't smell very nice at all. I was excited to find reference to home made dry laundry soap the other day on another blog I follow - The Sitting Tree - www.thesittingtree.blogspot.com. It is the same basic ingredients, you just don't have add any liquid.
So, I used 1 bar of Dr. Bronner's soap, I like the lavender scent, but there are others and un-scented as well. It is totally vegetable based, so no petro chemicals. I know lot of web sites refer to Fels Naptha and Zote soap, but I wanted to get as natural as I could. And then the other standard ingredients are washing soda and borax.
1 bar soap - grated finely
1 cup borax
1 cup washing soda
Mix well.
I found the finely grated soap incorporated easily with the powders and it smells awesome!! The whole process took about 20 minutes from beginning to end. Mix well and store in an air tight container. I happened to have a large plastic tub left over from some take out Hot and Sour Soup that worked perfectly. (I guess it was probably 1 quart, sized?) I have been using 2 tablespoons in my machine, which is a HE front loader and it works great. the clothes are clean and smell very fresh. The lavender scent is not strong at all when it's all said and done.
I have also made some felted wool dryer balls. (More on that to come) The soap already made the clothes come out of the dryer softer than store bought laundry detergent and now that I've added the dryer balls they really come out very nicely. Items I used to have to touch up with an iron are coming out wrinkle-free. That it a huge bonus for me!!
So, relative cost per batch:
borax - $4.95 per box - 10 cups per box - $0.50 per batch
washing soda - $2.99 per box - 7 cups per box - $0.43 per batch
Dr. Bronner soap - $3.99 per bar
Total cost per batch - $4.92 (I have not kept track of how many loads one batch will do, yet, but I'm not doing it just to save money, more because I know this is a better, more chemical free, alternative to Tide and such)
This project worked well for me. Winner!