I have long thick hair, and have been using one heaping teaspoon of baking soda to 16oz. of water.
Having a bowl under my head, I pour the cup of baking soda water over my hair. Scrub a bit. Pour water back into cup and pour over again, and scrub. I work in the water to the scalp. I have found that the oils come out quickly and turn the water milky. Rinse thoroughly with clean water.
Washing my hair in this way once a week or less, and I can use less than a gallon of water total, washing and rinsing.
