Your soap nuts will come with a muslin bag to put 5-7 nuts in and throw in the washing machine with hot water. Wash your clothes as usual. Replace the nuts after 4-5 washes, or when the flesh starts to lose its color and turn a bit gray.
Soap Nuts Liquid Recipe
This method takes a little more time but it saves energy as you can wash your clothes in cold water. The nuts need hot water to release the saponins. So do it before hand.
15-20 soap nuts 6 cups of water (plus more as you’re boiling). Use a sterilized container to hold the liquid.
Boil the soap nuts in the 6 cups of water for about 20 minutes. Add another cup of water. Boil for 10 minutes. Add another 2 cups of water and boil again for 10 minutes. Strain the nuts from the liquid and store in the sterilized container. It’s best to store the straight liquid in the refrigerator, as it will turn rancid after a while. Keep in the refrigerator for 1-2 weeks.
If you add a tablespoon of Citric Acid they say it can extend the shelf life of liquid for up to 4 weeks refrigerated.
You could also freeze it into ice cubes. And then you can just toss a couple of soap nut liquid ice cubes into your washing machine when you do the laundry. Make sure to label that so no one drinks it!
Liquid: Add 1/8 c. soap nut liquid to the wash, in lieu of regular laundry detergent.
You can find more recipes online.