What Is Cold Process Soap?
Cold process soap is made by combining oils and fats (such as coconut oil, olive oil, or shea butter) with a lye solution (sodium hydroxide dissolved in water). The saponification process, which is the chemical reaction that turns oils into soap, takes place over time rather than through heat, which is why it's called "cold process."
Once the ingredients are mixed, the soap is poured into moulds and left to harden. But while the soap may look ready to use immediately, it needs time to cure. This curing period can make all the difference in the texture, lather, and skin benefits of your soap.
What Is Curing?
Curing is the process during which the soap hardens and matures. The curing process allows excess water to evaporate from the soap, which makes it more solid and long-lasting. In addition to hardening, curing also ensures that the soap reaches a balanced pH level and allows the chemical reaction between oils and lye to fully complete.
While the soap may feel solid after a day or two, the curing time is crucial to ensure the soap is gentle on the skin, has a rich lather, and doesn't irritate or dry out the skin.
How Long Does Cold Process Soap Need to Cure?
The curing time for cold process soap is 4-6 weeks, though it can vary depending on a few factors, such as the ingredients used, the size of the soap batch, and environmental conditions.
- 4-6 Weeks: This is the general recommendation for most cold process soaps. During this time, the soap will gradually lose moisture, harden, and achieve the optimal balance for skin use.
- Shorter Curing Time (2-3 Weeks): While it’s possible to use soap after just a couple of weeks, the soap will be softer and more likely to break down faster in the shower. Additionally, a soap that hasn't fully cured may still have an elevated pH level or insufficiently processed oils, which could cause skin irritation.
- Longer Curing Time (up to 8 Weeks): Some soap makers choose to let their soap cure for longer than the typical 4-6 weeks. Extended curing time can result in an even harder bar of soap, which lasts longer, and it may offer a more mild, silky feel. If you’ve added extra oils or butters, or if you live in a humid environment, a longer cure may be a good idea.
Why Does Soap Need to Cure?
Excess Water Evaporation: Freshly made soap has a high moisture content. Curing allows excess water to evaporate, which results in a firmer and longer-lasting bar of soap.
Saponification Completion: Saponification doesn’t stop the moment the soap hardens. The process continues during curing, which ensures that all of the oils and lye have fully reacted, leaving no trace of lye in the final product. This ensures the soap is safe to use.
Improved Lather and Skin Benefits: Soap that has been properly cured often has a better lather and is more gentle on the skin. During the curing process, the chemical reactions also help create a smoother texture.
Balanced pH: Lye has a very high pH, which can irritate the skin if not fully reacted. Proper curing lowers the pH of the soap, making it more suitable for daily use.
Longer Shelf Life: Well-cured soap lasts longer both in storage and when used. A properly cured bar will maintain its shape and effectiveness, while a poorly cured bar can break down quickly and become mushy.
Factors That Affect Curing Time
While 4-6 weeks is a good guideline, the time it takes for soap to cure can vary depending on several factors:
- Type of Oils Used: Hard oils like coconut oil and palm oil tend to make harder bars that may require less curing time. On the other hand, soaps that are made with softer oils like olive oil or avocado oil might need more time to fully harden.
- Humidity and Temperature: The climate where you live can affect how quickly the soap cures. Soap cures best in a cool, dry, and well-ventilated area. Humidity can slow down the curing process, while high temperatures can cause the soap to crack or shrink.
- Size of the Soap Bars: Larger bars of soap will take longer to cure than smaller ones because they have more moisture inside. If you make larger batches, be prepared to extend the curing time.
- Additives and Extras: If you add herbs, exfoliants, or milk to your soap, they may slightly alter the curing time. Certain additives can also affect the hardness and pH, so it’s essential to consider these when determining the right cure time.
How to Cure Soap
Here are a few tips to help ensure your soap cures well:
- Place Soap in a Cool, Dry Area: Choose a place that’s out of direct sunlight, and avoid places with high humidity or moisture.
- Lay Soap on a Dry Surface: Place the soap on a surface that allows air to circulate around it.
- Flip the Soap Bars Occasionally: Once every few days, flip the soap bars to ensure even curing on all sides.
- Check for Hardness: After about 4 weeks, you can check the soap for hardness by gently pressing a finger into the bar. If it feels firm and the fingerprint doesn’t remain, your soap is likely ready.
Final Thoughts
Curing cold process soap is an essential step that shouldn’t be rushed. While it may be tempting to start using your soap right away, taking the time to let it cure will give you a much better end result. Your soap will be smoother, harder, and gentler on the skin, and it will last longer.
So, be patient. Your skin will thank you for it!