Making lavender shampoo bars is a rewarding way to combine the gentle cleansing power of cold-process soap with the calming, antimicrobial benefits of lavender. Below you’ll find a tested recipe, step-by-step instructions, and tips to ensure your bars turn out beautifully.

Ingredients & Equipment

Oil Blend (makes about 1 kg of soap base)

  • 350 g olive oil - rich in antioxidants, gentle on the scalp
  • 250 g coconut oil - provides lather and cleansing (use 20-25% for non-drying bars)
  • 200 g castor oil - boosts creamy lather and conditioning
  • 100 g shea butter - adds moisturizing slip and hardness
  • 100 g avocado oil - penetrates hair shaft for softness

Lye Solution

  • 184 g distilled water (use ice to keep temperature low)
  • 120 g sodium hydroxide (lye) - always handle with gloves, goggles, and in a well-ventilated area

Lavender Additions

  • 40 g dried lavender buds - lightly crushed for scent and gentle exfoliation
  • 15-20 g lavender essential oil (pure, 40/42 or high-altitude) - avoid fragrance oils; use therapeutic grade for lasting scent

Step-by-Step Instructions

  1. Prepare your workspace. Cover surfaces with newspaper, wear long sleeves, gloves, and safety goggles. Measure all oils (except the butter) and heat gently until melted. Let cool to about 40°C (104°F).
  2. Make the lye solution. Slowly add lye to water (never the reverse) while stirring. The mixture will get very hot. Let it cool to the same temperature as your oils (around 40°C).
  3. Combine oils and lye. Pour the lye solution into the oils. Use an immersion blender (a “stick blender”) to blend until ‘trace’ - the point where the batter thickens enough to leave a visible ribbon on the surface when drizzled.
  4. Add botanicals and scent. Quickly stir in the lavender essential oil and the crushed dried buds. Do not overmix once essential oils are added or they may dissipate.
  5. Pour into a mold. A silicone loaf mold works best. Tap the mold on the counter to release air bubbles. Gently press a few extra lavender buds on top for decoration.
  6. Insulate and saponify. Cover the mold with a towel or cardboard. Let it sit undisturbed for 24-48 hours. After that, check if the soap is firm enough to cut. If it feels soft, wait another 12 hours.
  7. Cut and cure. Slice the loaf into bars (about 2.5 cm / 1 inch thick). Place them on a rack in a cool, dry, dark place. Cure for 4-6 weeks - this allows excess water to evaporate and the bars to become mild and hard.

Expert Tips for Lavender Shampoo Bars

  • Do not scent with buds alone. Whole lavender buds add only a faint herbal note; they can also turn brown or cause scratchy bits. Always pair them with a high-quality essential oil.
  • Watch the discoloration. Pure lavender essential oil (especially high-altitude type) can turn the batter a light tan or pinkish-brown. That’s normal - don’t try to whiten it with titanium dioxide unless you want a muted lavender.
  • Adjust for hair type. For oily hair, increase coconut oil to 30% and reduce shea butter. For dry or curly hair, add 5% jojoba oil (swap out some olive oil) and double the superfat to 8%.
  • Test the pH. After 4 weeks of cure, a properly formulated shampoo bar should have a pH around 8-9. If it’s above 10, let it cure longer. For low-pH hair washing, follow with a diluted vinegar rinse (1 tbsp apple cider vinegar in 1 cup water).

Final word: Lavender shampoo bars are gentle, aromatic, and eco-friendly. With patience during the cure, you’ll create bars that lather well, clean effectively, and leave hair with a calming floral scent. Always patch-test any new bar on a small section of hair first. Enjoy your handmade, lavender-infused haircare!