Cold process soap: a step-by-step guide

Understanding the cold process technique

Cold process soap making is a traditional method that combines oils or fats with an alkali to create a chemical reaction called saponification. Using this technique, soap makers can control every aspect of their product, from the choice of oils to the final scent. Cold process soap cures slowly, allowing excess water to evaporate and resulting in a longer-lasting bar. This curing phase typically lasts between four and six weeks. During this time, the soap becomes harder and milder on the skin. Beginners often worry about working with lye, but with proper safety equipment and respect for the process, it is straightforward to handle. The end result is a handcrafted soap bar that retains natural glycerin—a humectant that attracts moisture to the skin.

Choosing sustainable ingredients

Selecting sustainable ingredients is at the heart of Waterfall Glen Soap Company’s philosophy. We source organic olive oil, sustainably harvested coconut oil, and fair-trade shea butter for our recipes. Using plant-based oils not only supports responsible agriculture but also yields a luxurious, creamy lather. When possible, we purchase from local Illinois farms to reduce transportation emissions. Our essential oils for scent come from certified organic growers who practice crop rotation and water conservation. We avoid palm oil unless it carries RSPO certification to ensure no tropical rainforests are harmed. By choosing biodegradable colorants like clays and plant powders, we minimize environmental impact and avoid synthetic dyes that can pollute waterways.

Safety tips for soap making

Working with lye requires respect and preparation. Always wear protective goggles, a long-sleeve shirt, and nitrile gloves to prevent skin and eye contact. Measuring ingredients by weight using a digital scale ensures accurate lye-to-oil ratios. Mixing lye into water—not the other way around—prevents dangerous splashes. Perform your work in a well-ventilated area or beneath a fume hood to avoid inhaling vapors. Keep vinegar on hand as a neutralizer in case of spills. To test trace, use a stick blender and look for a ribbon-like pattern when you drizzle soap batter onto itself. Pouring at light trace helps ensure proper mixing of additives. Finally, label and date your molds so you can track curing time and batch details for quality control.

Customizing scents and additives

Customizing your soap allows endless creative expression. Essential oils such as lavender, peppermint, and eucalyptus each bring unique aromatherapy benefits. Adding colloidal oats or finely ground oats offers gentle exfoliation and skin soothing properties. For color, spirulina powder yields a soft green hue, while French pink clay adds blush tones and detoxifying minerals. If you prefer a swirl pattern, pour two or three differently colored soap batters into the same mold and use a chopstick to create intricate lines. Activated charcoal can create dramatic black stripes and assist with oily or acne-prone skin. Finally, pressing dried calendula petals or rose buds onto the surface before the soap hardens adds a decorative touch and gentle exfoliant.

Curing, cutting, and storage

Once the soap batter is poured into molds, cover it with plastic wrap and insulate with towels to encourage gel phase. After 24 to 48 hours, unmold the soap and slice it into bars using a stainless-steel cutter or sharp knife. Place the bars on a rack with ample air circulation and turn them occasionally to ensure even drying. Avoid storing soap where humidity is high, as moisture can soften bars and shorten their lifespan. After four to six weeks of curing, each bar reaches optimal hardness and mildness. Store finished bars in a dry, cool location—ideally in paper or cardboard packaging to allow continued breathability. Properly cured and stored soap can last up to a year without losing quality.