pediaCold-process soap, is a type of handmade soap produced by mixing vegetable oils with sodium hydroxide (NaOH) at low temperatures (30–50°C) and allowing the saponification reaction to complete in the mold. Unlike industrial soap production, in the cold process method, glycerin remains in the soap’s structure, essential oils are better preserved thanks to the low temperature, and each recipe creates a unique formulation. This article discusses what cold process soap is, how it differs from traditional and industrial soap, the production process, and its place in the Turkish soapmaking tradition.
This article is intended for general informational purposes only. It does not make any claims regarding treatment.
What is cold process soap?
The term “cold process” refers to the saponification reaction being carried out without the application of external heat—or with minimal heat. Oils and a NaOH solution are typically combined at temperatures between 30–50°C; the reaction’s own exothermic heat (the heat released when NaOH reacts with water) initiates saponification. The soap batter is poured into a mold, and saponification is largely completed in the mold, followed by a 4–6-week curing process.
“Cold press” or “cold process”?
In Turkish, the term “cold press soap” is commonly used, but the technically correct term is “cold process.” “Cold press” actually refers to an oil extraction method—such as the cold pressing of olive oil or nut oil. “Cold process,” on the other hand, is a soap-making method. This terminological confusion is not unique to Turkey; it is also occasionally seen in the international soapmaking community.
Cold Process vs. Industrial Soap: Key Differences
Glycerin: The Most Critical Difference
Glycerin is naturally produced during the saponification reaction—approximately 10–14 grams of glycerin are formed from every 100 grams of oil. In industrial soap production, this glycerin is typically separated using the “salting out” method and sold at a higher price to the cosmetics, pharmaceutical, and food industries. In cold-process soaps, however, the glycerin remains in the soap’s structure. Glycerin is a natural humectant (moisture-attracting agent) that helps maintain the skin’s moisture balance—this is the main reason why cold-process soaps feel “more moisturizing.”
Temperature and Ingredient Preservation
Cold process soap is produced at 30–50°C; the industrial continuous process operates at temperatures of 200°C and above. Lower temperatures better preserve the volatile components of essential oils, natural antioxidants (tocopherols, polyphenols), and delicate bioactive compounds.
Formula Originality vs. Standardization
In cold process soapmaking, every recipe is unique—different oil combinations, essential oil blends, and additives provide endless variety. In industrial production, however, cost optimization and standardization take priority; production typically uses a limited number of oils (palm, palm kernel).
The Cold Process Soap-Making Process
1. Recipe Design and Lye Calculation
Each soap recipe is calculated based on the SAP (saponification) values of the oils used. The amount of NaOH required for the saponification of each oil varies. Lye calculators (such as SoapCalc or the Bramble Berry Calculator) automate this calculation. The “superfat” ratio—typically 5–8%—is the amount of unsaponified oil intentionally left in the recipe to provide a moisturizing effect on the skin.
2. Preparing the Oils and Lye
Solid fats (coconut, palm, cocoa butter) are melted; liquid oils (olive oil, walnut oil) are added. NaOH is dissolved in distilled water or an alternative liquid (goat’s milk, aloe vera gel)—during this stage, the exothermic reaction can cause the temperature to exceed 80°C.
3. Trace and Molding
“Trace” is the point at which the soap batter reaches a pudding-like consistency and a drop of batter left on the surface leaves a trail — this indicates that emulsification has occurred. During the trace stage, essential oils, colorants, and additives (activated carbon, bentonite clay, sulfur, etc.) are added. The paste is molded and goes through the “gel phase” for 24–48 hours—during this stage, saponification is largely complete.
4. Curing: 4–6 weeks
The soap bars removed from the molds are cured for 4–6 weeks in a well-ventilated, cool, and dry environment. During this time, the remaining saponification is completed, excess water evaporates (the soap hardens), the crystalline structure matures, and the pH stabilizes. The curing period is a critical determinant of soap quality—insufficient curing produces soap that is soft, melts quickly, and may potentially cause skin irritation.
Cold Process and the Turkish Soapmaking Tradition
Turkey holds an important place in the history of soapmaking. The spread of the Aleppo soap tradition to Anatolia has fostered a deep-rooted soapmaking culture, particularly in Antakya and Southeastern Anatolia. Local traditions such as Siirt bıttım soap, Kastamonu soap, and Thracian bay leaf soap represent different variations of the hot process method. Modern Turkish natural soap producers combine this traditional heritage with scientific soapmaking principles—the cold process is the most widely used technique in this synthesis.
Advantages and Limitations of Cold-Process Soap
Advantages
The main advantages of cold-process soap: natural glycerin content (humectant—moisture-attracting effect), low-temperature production (essential oils and sensitive ingredients are preserved), endless recipe variety (different oil combinations, essential oil blends, natural colorants), no need for synthetic detergents or preservatives (high pH naturally inhibits microbial growth), potential for sustainability (minimal energy consumption, biodegradable), and artisanal value (each bar is unique—the opposite of industrial standardization).
Limitations
Cold-process soap also has limitations: it requires a curing period of 4–6 weeks (cannot be used immediately), each batch may vary slightly (full standardization is difficult), the alkaline pH cannot be altered (all true soaps have a pH of 9–10), its shelf life may be limited compared to industrial products (it contains no preservatives, though low water activity balances this out), production requires knowledge and skill (lye calculation, trace management, safety), and the cost is higher compared to industrial production (handwork, vegetable oils, curing time).
Superfat: The Secret to Moisturization in Cold Process
One of the most important technical concepts in cold process soapmaking is the “superfat” ratio. In the recipe, the amount of NaOH is intentionally calculated to be 5–8% less than what is needed to saponify all the oils. This leaves unsaponified free fatty acids in the soap—these oils provide a moisturizing and softening effect on the skin. The superfat ratio is the most important moisturizing parameter that a soapmaker can control. A very low superfat percentage (0–2%) produces hard, drying soap; a very high superfat percentage (10%+) produces soft, easily melting soap that increases the risk of DOS (orange spots).
Frequently Asked Questions
Are “cold press” soap and “cold process” soap the same?
Although “cold press soap” is commonly used in Turkish, the technically correct term is “cold process.” “Cold press” refers to an oil extraction method; “cold process” refers to a soap-making method.
Why does cold process soap need to cure for 4–6 weeks?
During the curing period, the saponification process is completed, excess water evaporates, the crystalline structure matures, and the pH stabilizes. Insufficient curing results in soft and potentially irritating soap.
Is there glycerin in cold process soap?
Yes—glycerin, a natural byproduct of saponification, remains in the structure of cold process soap. In industrial production, however, it is usually separated out.
What is the pH of cold process soap?
All true soaps have an alkaline pH—typically pH 9–10. This is a natural result of the saponification process. Healthy skin quickly restores this temporary pH increase to normal levels.
References
1. Spitz, L. (2009). Soap Manufacturing Technology. AOCS Press.
2. Cavitch, S. M. (1997). The Natural Soap Book. Storey Publishing.
3. Dunn, K. M. (2010). Scientific Soapmaking. Clavicula Press.
4. EU Regulation (EC) No. 1223/2009 on cosmetic products.