If you've ever wanted to turn oils and lye into beautiful, skin-loving bars of soap—you're in the right place. In this guide, I'm walking you through exactly how to make cold process soap, the traditional method that lets you create customized, natural bars right from your own kitchen. Whether you want to control ingredients, avoid harsh chemicals, or just love a good DIY, cold process soapmaking is a craft you'll want to come back to again and again.
What Is Cold Process Soap Making?
Cold process soapmaking is the art of turning oils and lye into soap through a chemical reaction called saponification. It differs from melt and pour (which uses pre-made soap bases) and hot process (which speeds things up with heat). Cold process allows complete control over your ingredients and gives a smooth, long-lasting bar.
Cold Process vs. Melt & Pour:
- Melt & Pour: Faster, beginner-friendly, but limited customization.
- Cold Process: More advanced, more natural, fully customizable.
Cold Process vs. Hot Process:
- Hot process soap is cooked, giving it a rustic look.
- Cold process cures over time and has a smooth finish.
A Quick Look at Soapmaking History
Soapmaking dates back thousands of years. Ancient Babylonians used a primitive form of soap in 2800 BCE, and over time, soap became both a necessity and a luxury. Cold process soap, as we know it today, is rooted in traditional European techniques, passed down and refined over generations. Today, we mix tradition with creativity—making soap not just practical but beautiful.
Cold Process vs. Melt & Pour (Compared Simply)
| Feature | Cold Process | Melt & Pour |
|---|---|---|
| Customization | High | Moderate |
| Cure Time | 4–6 weeks | None |
| Skill Level | Intermediate | Beginner |
| Natural Ingredients | Full control | Limited |
| Appearance | Smooth, artisanal | Glossy, commercial |
Getting Your Workspace Ready
Before diving into oils and lye, prep your space. Choose a well-ventilated area with a stable work surface. Cover countertops, keep pets and kids away, and gather everything you'll need. You’ll also need a "cooling zone" (where the soap sits in the mold) and a spot to cure your soap for 4–6 weeks.
Workspace Checklist:
- Clean counter with newspaper or reusable cloths
- Measuring tools
- Safety gear (goggles, gloves, apron)
- Soap molds and liners
- Spatulas, bowls, stick blender
Safety First (Always!)
Let’s talk lye. Sodium hydroxide (NaOH) is essential to soapmaking, but it’s also caustic and can cause burns. Don’t let that scare you—just be smart and safe.
Lye Safety Tips:
- Always wear gloves and goggles
- Mix lye into water (not the other way around!)
- Never inhale fumes
- Work in a ventilated area
- Store lye away from kids and pets
Supplies & Tools You'll Need
- Digital scale
- Thermometer (laser or probe)
- Stick blender
- Mixing bowls (stainless steel or heat-safe plastic)
- Silicone or wooden mold
- Measuring spoons & cups
- Spatula and whisk
- Safety goggles, gloves, apron
Can You Use Plastic Molds? Yes, but make sure they are heat-resistant. Some plastics warp under heat from saponification.
Ingredients Breakdown
Soap needs three core components: oils, water, and lye. Everything else is bonus.
Base Oils:
- Olive Oil: gentle and conditioning
- Coconut Oil: cleansing and creates lather
- Palm Oil: hardens the bar (use sustainably!)
- Castor Oil: boosts bubbles and conditioning
Lye:
Sodium hydroxide is necessary to turn oils into soap.
Water:
Use distilled water to prevent mineral contamination.
Add-Ins:
- Essential Oils or Fragrance Oils
- Natural Colorants (clays, charcoal, turmeric)
- Exfoliants (oats, poppy seeds, coffee grounds)
Beginner-Friendly Soap Recipe
Ingredients:
- 300g Olive Oil
- 200g Coconut Oil
- 100g Palm Oil (RSPO-certified)
- 50g Castor Oil
- 140g Distilled Water
- 66g Sodium Hydroxide (NaOH)
- 20g Essential Oil (Lavender, Peppermint, etc.)
Method: Follow the step-by-step section below!
Let’s Make Cold Process Soap – Step by Step
Step 1: Weigh Your Ingredients
Measure your oils, lye, and water using a digital scale. Accuracy is key.
Step 2: Make Your Lye Solution
In a well-ventilated area, slowly add lye into the water (never the reverse!). Stir until dissolved. Let cool.
Step 3: Melt and Combine Oils
Melt your solid oils first, then add liquid oils. Stir well.
Step 4: Check Temperatures
Both lye solution and oils should be around 100°F (38°C) when you combine them.
Step 5: Mix to Trace
Using a stick blender, mix until the batter reaches “trace”—a pudding-like texture.
Step 6: Add Fragrance & Color
Add your essential oil and colorants at light to medium trace. Stir well.
Step 7: Pour Into Molds
Pour the batter into your soap mold. Tap gently to release air bubbles.
Step 8: Insulate or Not (Gelled vs Ungelled)
Cover with a towel and insulate for a gel phase, or leave uncovered for a creamier finish.
Step 9: Unmold & Cut
After 24–48 hours, unmold and slice into bars.
Step 10: Cure for 4–6 Weeks
Let the bars cure in a cool, dry area with airflow. This hardens the bars and completes saponification.
Troubleshooting Common Issues
- Soap seized? You may have added fragrance too early or used a fast-accelerating oil.
- Cracks or overheating? Try soaping at lower temps and avoid over-insulating.
- Soda ash? It’s cosmetic. Spray with alcohol or cover tightly after molding.
- Soft soap after days? Could be too much water or not enough lye.
How to Cure, Store, and Wrap Your Soap
- Cure on open shelves for 4–6 weeks
- Turn bars weekly to prevent warping
- Store in a dry, cool area
- Wrap with paper bands, boxes, or leave naked if gifting
FAQs
How long does cold process soap take to cure?
Usually 4 to 6 weeks. This allows excess water to evaporate, resulting in a harder, longer-lasting bar.
Can I make soap without lye?
Technically, no. All true soap requires lye. But you can use pre-made bases in melt & pour soap if you want to skip this step.
How much essential oil should I use in soap?
Typically 3–5% of your oil weight. For a 1000g oil recipe, that’s about 30–50g.
Can I use plastic molds for cold process soap?
Yes, but avoid thin or flimsy plastics. Silicone or HDPE are safest.
When can I unmold cold process soap?
After 24 to 48 hours, depending on the recipe and mold type.
Can I sell homemade soap legally?
In most regions, yes—but check your local regulations. Labeling laws and testing may apply.
What temperature should soap ingredients be mixed at?
Around 100°F (38°C) is ideal for both oils and lye.
Why is my soap soft after 24 hours?
It might need more time to saponify or cure. Double-check your recipe and allow for a longer mold time.
What’s the difference between gelled and ungelled soap?
Gelled soap goes through full saponification quickly and looks more vibrant. Ungelled is creamier and often preferred for milk soaps.
Final Thoughts
Making cold process soap is part science, part art, and totally rewarding. Whether your first batch turns out perfect or perfectly imperfect, you’ve created something useful, beautiful, and entirely your own. Have fun with it, share your creations, and tag us if you post them!
Ready to try new scents or dive into color design? Check out our essential oil collection or subscribe for more DIY guides. Happy soaping! 🧼
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