Rice water has been used for centuries as a hair rinse. It contains amino acids, B vitamins, starch, and inositol, which can help smooth the hair cuticle, add shine, and provide gentle conditioning. When used as the water phase in a shampoo bar, it makes a lovely traditional addition. Below is a reliable cold-process recipe, along with key tips for success.

Prepare the rice water first

You can use fresh or fermented rice water.

  • Fresh rice water: Rinse 1/2 cup of rice, then soak it in 2 cups of water for 30-60 minutes. Strain and chill.
  • Fermented rice water: Let the rinsed rice soak at room temperature for 12-24 hours until slightly sour, then strain and chill.

For this recipe you will need 106 g of cold rice water. Keeping it cold helps control the heat when you mix it with lye.

Cold-process rice water shampoo bar recipe

This recipe makes about 680 g of soap before curing, roughly 6-7 bars depending on your mold. It is formulated with a 5% superfat to help offset the cleansing strength of the coconut oil.

Oils and butters

  • 150 g coconut oil (30%) - cleansing and bubbly lather
  • 150 g olive oil (30%) - mild conditioning
  • 50 g castor oil (10%) - creamy, stable lather
  • 75 g avocado oil (15%) - nourishing and scalp-friendly
  • 50 g shea butter (10%) - adds hardness and moisture
  • 25 g sweet almond oil (5%) - light conditioning

Lye and liquid

  • 71 g sodium hydroxide (lye)
  • 106 g cold rice water
  • Optional: 1 teaspoon sodium lactate to help harden the bars
  • Optional: 12-15 g essential oil blend, such as rosemary, lavender, or tea tree

Important: Always run any changes through a soap calculator. Always wear goggles, gloves, and long sleeves when working with lye.

Instructions

  1. Prepare your mold and safety gear. Work in a well-ventilated area.
  2. Place the cold rice water in a heat-safe pitcher. Slowly add the sodium hydroxide to the rice water, never the other way around. Stir gently until fully dissolved. The mixture will get hot and may become slightly cloudy; this is normal.
  3. Set the lye-water aside to cool to around 90-110°F. If you are using sodium lactate, stir it in once the lye water has cooled.
  4. Melt the coconut oil and shea butter gently, then combine with the liquid oils. The oil blend should also be around 90-110°F.
  5. Pour the lye-water into the oils. Use a stick blender in short bursts until you reach a light trace.
  6. Add your essential oil blend, if using, and stir gently by hand. Rice water can slightly thicken trace, so avoid over-blending.
  7. Pour the batter into the mold, tap out air bubbles, and insulate lightly. Let it sit for 24-48 hours before cutting.
  8. Cut into bars and cure in a cool, dry place with good airflow for 4-6 weeks. This allows the soap to harden and become milder.

Using your rice water shampoo bar

Because this is a true soap-based bar, its pH is naturally alkaline. This is normal for cold-process soap, but hair prefers a slightly acidic environment. To prevent a waxy or tangly feel, follow every wash with a diluted apple cider vinegar rinse: mix 1 part apple cider vinegar with 4 parts water, pour over the ends, leave for a moment, and rinse lightly.

If you have hard water, soap-based shampoo bars can leave mineral buildup over time. In that case, a pH-balanced syndet shampoo bar may be a better choice. You can also incorporate rice water into a syndet formula at 3-5% of the batch weight, but you must include a broad-spectrum preservative because the product will contain water.