(Makes approximately 5 cups)
2 cups (finely) grated castile soap*
1 cup borax
1 cup baking soda
1 cup soda ash (washing soda)
*(I love, love, love Dr. Bronners. One and a half .5 oz bars makes about two cups. So far, peppermint is everyone's favorite for laundry. So fresh.)
Mix everything together, and store in an airtight jar. Depending on your water, you might need to adjust the sodas a bit, and the amount used per load. I use 1/8 cup per load. You may need to give the jar a shake once in a while to prevent the soap flakes from settling to the bottom.