After I finished my last batch of eco-laundry detergent, I was looking through my neighbourhood organic store called Nuthouse and inquired about these. Apparently they were an absolutely natural, biodegradable, petroleum free version of what we have come to consider a cleaning product! Of course there was something before there was laundry detergent.... And it was a fruit!
Soap Nuts/Soap Berries have a lot of saponin on their shells, which lowers the surface tension of water and so allows it to act as a cleaning agent. Or something like that....
There's some actual great information here!
Generally things recommend 4 or 5 nuts per wash but I do a triple loader only once every 3 weeks or so, so I put in 10 nuts per load. They come with a mesh cotton bag that you just throw in the washer with your clothes, and then you hang it out to try for next time! I've heard of varying re-uses from 4 to 10 times. See how stuff feels as you go. A homemade science experiment!