Making plant soap is not very difficult, it is about letting horse chestnuts boil in a pot in a solar oven during a day so that all the saponins are extracted. But the dried horse chestnuts need to be broken first as shown on the video (you can see the complex technics used ;). After having boiled long enough, you can pass them in mixer to get better extraction, then filter them. The result keeps a few days, not a problem as it is easy to make or you just let it concentrate in the solar oven, or keep it sterilized. A nice mild soap to wash anything, very good for laundry.