First, find a container with a lid. Pour the rice washing water from the first 2-3 rinses each day into it. Usually, sediment forms by the next day. Gently pour off some of the clear water on top to increase the concentration. Then add fresh rice washing water from that day. Repeat this process the next day—pour off some clear water and add fresh rice washing water. After 3-4 days, the container will contain rice washing water from 3,water from 3-4 days ago, 2 days ago, and fresh water all mixed together. This rice water has started fermenting slightly and may even have a faint sour smell (since the oldest part has been sitting for 3-4 days).
When it's time to wash your hair, pour this mixture into a basin, making sure to include the sediment at the bottom of the container. Since the rice water is cold, add some hot water to it and stir until well combined. The rice water shouldn't be too hot—warm is fine. Then add a little vinegar, and you're ready to wash.It's best to comb your hair before washing. During the wash, gently massage your hair with your hands and use your fingers to massage your scalp, ensuring the rice water thoroughly cleans both your hair and scalp. If your hair tends to be oily, you can wash it a bit longer. It's similar to washing dishes with rice water—if the dishes are greasy, I'll soak them in the rice water a bit longer first, and then the grease comes off easily.Once your hair feels sufficiently clean, discard the rice water and move on to conditioning. Add the juice of one lemon to clean, lukewarm water. Soak your hair in this mixture for a few minutes to soften it and impart a fresh lemon scent. Then rinse thoroughly with clean water to complete the wash.Use 100% pure lemon juice with no additives—it's cheaper than fresh lemons and lasts longer. After washing, skip the blow dryer. Pat your hair with a towel and let it air dry. Avoid combing when wet; wait until it's almost dry to minimize hair loss. Clean, warm water thoroughly cleans your hair—one or two washes are usually sufficient.