Refined hemp oil is a valuable ingredient in handcrafted soap. It contributes conditioning properties, a stable colour, and a mild aroma that does not interfere with added fragrances. This article covers the technical aspects of using refined hemp oil in cold-process and hot-process soap making.
Why soap makers use refined hemp oil
- Conditioning properties. Hemp oil's fatty acid profile produces a mild, moisturizing bar that suits sensitive skin formulations.
- Light colour. Refined oil does not turn the soap green (as virgin hemp oil would), allowing predictable colours from added pigments.
- Neutral aroma. Does not interfere with essential oils or fragrance oils.
- Linoleic acid content. Contributes to a fluffy lather (when combined with other oils).
- Skin-friendly profile. Low irritation potential, suitable for face-bar formulations.
Saponification values
For cold-process soap calculations, hemp oil's saponification values are:
- SAP NaOH (sodium hydroxide): 0.134
- SAP KOH (potassium hydroxide): 0.190
For a bar of soap using 100 grams of hemp oil, you would need approximately 13.4 grams of sodium hydroxide. Always verify with a current saponification calculator before formulating; values vary slightly between sources.
Typical inclusion rate
Refined hemp oil typically comprises 10-30 percent of the oil weight in a soap recipe. Above 30 percent, the soap can become softer due to hemp's high polyunsaturation. Below 10 percent, the contribution to the finished bar is minimal.
Sample cold-process soap recipe
Yields 12 bars at ~110g each. Approximately 8 weeks total time (mixing to cure).
Oil phase (1000g total)
- Coconut oil: 250g (25%)
- Olive oil: 350g (35%)
- Refined hemp oil: 200g (20%)
- Castor oil: 50g (5%)
- Palm or sustainable substitute: 150g (15%)
Lye solution
- Distilled water: 380g
- Sodium hydroxide: 140g (calculate based on actual recipe for 5% superfat)
Optional additives
- Fragrance or essential oils: 30-40g
- Colourants (mica, clay): 1-2 teaspoons
- Hemp hearts (texture/visual): 2-3 tablespoons
Method (cold process)
- Measure all ingredients precisely by weight.
- Combine sodium hydroxide with cold distilled water (always add lye to water, not the reverse). Stir until dissolved. The solution will heat significantly. Set aside to cool to about 38°C (100°F).
- Combine all oils in a separate container. Warm gently to 38°C if any are solid.
- When both are at similar temperatures, slowly pour the lye solution into the oils while stirring with an immersion blender.
- Blend in short pulses until the mixture reaches "trace" (the texture of thin pudding).
- Add fragrance, colourants, and any additives at trace. Mix thoroughly.
- Pour into a soap mould. Cover with parchment and a towel.
- Allow 24-48 hours to fully saponify. Unmold and cut into bars.
- Cure bars on a rack in a cool, ventilated area for 4-6 weeks. The saponification continues during this time, and the bars harden.
What hemp oil contributes to the finished bar
- Soft, conditioning lather
- Mild, moisturizing feel on skin
- Subtle green-tinted natural appearance (unless colourants used)
- Skin-friendly profile suitable for facial use
Safety considerations
Soap making with sodium hydroxide requires proper safety procedures:
- Wear safety goggles and gloves at all times
- Work in a well-ventilated area
- Add lye to water, never water to lye (causes violent reaction)
- Keep children and pets out of the workspace
- Have white vinegar nearby (neutralizes lye spills on surfaces, NOT on skin)
- For skin contact: flush with cool water; do not use vinegar
Storage and shelf life
Cured soap with hemp oil typically has a shelf life of 12-18 months. The polyunsaturated fats in hemp can develop "dreaded orange spots" (oxidation) over time if stored in warm or humid conditions. Store in a cool, dry place. For longer shelf life, consider higher percentages of more stable oils (palm, lard, beeswax) in your formulation.
Hot-process variation
Hot process soap making cooks the soap to accelerate saponification. With hot process, the soap can be used within 1-2 weeks rather than waiting 4-6 weeks. Hemp oil works in hot process at the same percentages.