Hot Process Soap, What is it? - Overview

Hot process soap is another method of soap-making that involves using heat to accelerate the saponification process (the chemical reaction between oils and lye). Unlike cold process soap, which is made at room temperature and requires curing for several weeks, hot process soap is made by applying heat to the mixture, which speeds up the chemical reaction and allows the soap to be used sooner (usually within a few days).

How Hot Process Soap Is Made:

    Ingredients:

        Oils/Fats: Similar to cold process soap, oils such as olive oil, coconut oil, palm oil, shea butter, and castor oil are commonly used in hot process soap-making.

        Lye (Sodium Hydroxide): Lye is the alkaline solution that reacts with oils to create soap.

        Water: Water is mixed with the lye to form a lye solution.

        Optional Additives: Essential oils, fragrances, colorants, herbs, or exfoliants can be added for texture, scent, and appearance.

    Process:

        Mixing the Lye Solution: Just like cold process soap, the lye is mixed with water to create a lye solution.

        Heating the Oils: The oils and fats are typically heated to a higher temperature (around 140°F to 180°F), which speeds up the saponification process.

        Combining Oils and Lye Solution: After the oils are heated and the lye solution is prepared, they are combined and mixed until they reach "trace," which is the point at which the mixture thickens.

        Cooking the Mixture: The soap mixture is then placed in a slow cooker or double boiler and "cooked" for 1–3 hours. This heat accelerates the saponification process, breaking down the oils more quickly and turning the mixture into soap.

        Testing for Completion: Once the soap has cooked, it is tested to ensure the saponification process is complete. A simple way to check is by doing a pH test or taking a small sample and checking if it feels smooth and non-alkaline.

        Additives and Pouring: After cooking, any desired additives (such as essential oils or colorants) are mixed into the soap. The mixture is then poured into molds to set.

        Curing: Hot process soap requires less curing time than cold process soap, usually around 1–2 weeks, to allow excess moisture to evaporate and the soap to harden.

Key Characteristics of Hot Process Soap:

    Faster Turnaround Time:

        Hot process soap is ready to use much sooner than cold process soap because the saponification process is accelerated by the heat. While cold process soap requires weeks of curing, hot process soap often only needs a few days.

    Rougher Texture:

        Hot process soap tends to have a more rustic, textured appearance with less smoothness compared to cold process soap. This is because the soap is cooked, which can create a more uneven texture.

    Retains Glycerin:

        Like cold process soap, hot process soap retains the natural glycerin produced during saponification. Glycerin is a natural humectant that helps to moisturize the skin.

    Can Be Used Sooner:

        The accelerated saponification process means hot process soap can be used more quickly than cold process soap. While cold process soap can take 4–6 weeks to fully cure, hot process soap may only require a few days to a couple of weeks.

    Customizable Additives:

        Additives like essential oils, exfoliants, and colorants can be added after the cooking process to enhance the soap’s properties and appearance.

Benefits of Hot Process Soap:

    Quicker Results: Hot process soap can be used sooner than cold process soap, making it a good option for soap makers who need their soap ready more quickly.

    Natural Glycerin: Like cold process soap, hot process soap retains natural glycerin, which is moisturizing and gentle on the skin.

    More Robust Scents: Since essential oils are added after cooking, hot process soap can maintain stronger fragrances than cold process soap.

    Milder on the Skin: The heat used in the process allows for a smoother, more refined lather that’s gentle on the skin, especially if nourishing oils are used.

Challenges of Hot Process Soap:

    Rougher Appearance: Hot process soap can have a rougher, less polished appearance compared to cold process soap. The texture may be more irregular and uneven.

    Time-Consuming Cooking Process: While it takes less time than curing cold process soap, the hot process still requires a few hours of cooking, which adds an extra step to the process.

    More Difficult to Control: The heat and cooking process can sometimes cause colorants, fragrances, or additives to behave unpredictably, so they may not blend as smoothly as with cold process soap.

Comparison of Hot Process and Cold Process Soap:

Feature              Cold Process Soap    Hot Process Soap

Curing Time    4–6 weeks        A few days to 1–2 weeks

Texture               Smooth, even appearance   Rustic, textured appearance

Lather Quality               Creamy, mild  Less creamy, but still good

Customizability           High     High, but more difficult to control

Heat     No external heat needed       Requires cooking with heat

Ease of Use     Requires patience and longer curing             Can be used more quickly

Conclusion:

Hot process soap is a fast and efficient soap-making method that uses heat to speed up the saponification process. It results in a more rustic, textured soap that can be used within days or weeks of making. The heat retains the beneficial properties of the oils and natural glycerin, providing a moisturizing and gentle soap. Hot process soap-making is ideal for those who want quicker results and enjoy a more handmade, rough texture in their soaps.