How to Make Dual Lye Soap
Creating Luxurious Cream Bars and Shaving Soaps
What is Dual Lye Soap?
Dual lye soap combines sodium hydroxide (NaOH) and potassium hydroxide (KOH) in a single recipe. This creates a unique soap with properties of both bar soap and liquid soap - firm enough to hold its shape, yet soft and creamy with exceptional lather.
Why Make Dual Lye Soap?
- Superior lather: Creates rich, creamy, stable lather that's perfect for shaving.
- Cream texture: Softer than bar soap, making it ideal for pressing into bowls.
- Faster cure: The KOH portion cures quickly, reducing wait time to 2-4 weeks.
- Customizable firmness: Adjust the NaOH:KOH ratio for your desired texture.
Common Uses:
- Traditional shaving soap for brushes and bowls
- Cream bars for face washing
- Luxury body bars with extra-creamy lather
- Pet shampoo bars (easier to work into fur)
NaOH:KOH Ratios
The ratio of NaOH to KOH determines your soap's final texture and properties.
| Ratio | Texture | Best Use |
|---|---|---|
| 80% NaOH : 20% KOH | Mostly firm bar | Long-lasting body bars |
| 70% NaOH : 30% KOH | Cream bar consistency | Face bars, moldable bars |
| 50% NaOH : 50% KOH | Soft and pliable | Shaving soap in bowls (Recommended) |
| 40% NaOH : 60% KOH | Very soft cream | Jar or container soap |
| 30% NaOH : 70% KOH | Paste-like | Squeeze tubes or jar soaps |
Step 1: Setting Up the Calculator for Dual Lye
The SoapMath calculator makes dual lye soap easy. Follow these steps:
Select Dual Lye Mode
In Step 1: Lye Selection, click on "Dual Lye (NaOH + KOH)". New options will appear for the ratio.
Set Your NaOH:KOH Ratio
Enter the NaOH percentage. The KOH percentage calculates automatically to total 100%.
Pro Tip
Adjust NaOH Purity
Enter your NaOH purity (usually 97-100%). KOH purity is already factored into the calculator's SAP values.
Purity Note
Step 2: Formulating Your Recipe
Water Calculation
A lye concentration of 33-35% works well. Shaving soaps often use slightly less water (35-38%) for a thicker paste.
Superfat Settings
- Shaving soap: 3-5% superfat for optimal lather
- Cream face bars: 5-7% superfat for conditioning
Oil Selection
Build a recipe optimized for lather. Shaving soap requires specific oils:
| Oil/Acid | Percentage | Property |
|---|---|---|
| Stearic Acid | 30-40% | Dense, stable lather (Crucial) |
| Coconut Oil | 30-35% | Big bubbly lather |
| Castor Oil | 10-15% | Slickness and lather boost |
| Olive Oil | 10-15% | Conditioning |
| Shea Butter | 5-10% | Creaminess |
Step 3: Making the Soap
Safety First
- Wear safety goggles and gloves at all times
- Work in a well-ventilated area
- Have vinegar ready to neutralize lye splashes
- Keep children and pets away
Preparing the Lye Solution:
Recommended Method: Combine Lyes First
Mixing:
Melt Oils
Melt your oils and stearic acid. Note that stearic acid has a high melting point (approx 158°F / 70°C).
Combine
Add the lye solution to the oils. Stearic acid reacts very quickly, so trace will happen fast.
Pour and Wait
Pour into molds or bowls. Let it rest for 24-48 hours before unmolding.
Troubleshooting
| If… | Then… | Solution |
|---|---|---|
| Soap is crumbly | High NaOH or stearic acid | Reduce stearic acid or increase KOH ratio next time |
| Soap is too soft/runny | High water or KOH ratio | Increase NaOH ratio or use a water discount |
| Poor lather | High superfat or low coconut/stearic | Check recipe balance and reduce superfat to 3-5% |
| Separation in mold | Emulsion failed (common with stearic) | Rebatch the soap by heating gently and re-mixing |
Ready to try dual lye?
Select 'Dual Lye' in the SoapMath calculator to get your exact NaOH and KOH weights.