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Saponification Reaction

Soap is essentially a chemical reaction product of oils and fats (such as palmitic acid and stearic acid in palm oil) and a strong base (such as sodium hydroxide (caustic soda), used in solid soaps, or potassium hydroxide (used in liquid soaps)) undergoing a saponification reaction, producing fatty acid salts (the main component of soap) and glycerin (a natural moisturizing ingredient that remains in handmade soaps but may be added or extracted in industrial soaps).

Palm oil's advantage lies in its high proportion of saturated fatty acids (approximately 40%-50% palmitic acid and 3%-6% stearic acid), which significantly enhances the hardness and stability of soap. It is often combined with oils like olive oil and coconut oil to achieve a balance between cleansing power and mildness.

Strictly control the ratio of raw materials:

The amount of sodium hydroxide used must be calculated using the "saponification value" (you can use an online "saponification value calculator"). Excessive alkali will result in a pungent odor and leave skin feeling tight after washing; excessive oil will cause the soap to become soft and prone to rancidity. The palm oil content should not be too high (no more than 50% is recommended). Excessive use will result in a soap that is too stiff and lacks lather, and excessive cleansing power may damage the skin barrier.

Safe Handling of Sodium Hydroxide:

When dissolving lye, always dissolve it in water and do so in a well-ventilated area to avoid inhaling irritating fumes (wear a mask).

If lye accidentally comes into contact with skin, immediately rinse with plenty of running water for at least 15 minutes. If it gets into eyes, rinse and seek medical attention immediately.

Control Temperature and Trace Status:

The temperatures of the oil and lye should be close (temperature difference ≤ 5°C). Too high a temperature will cause saponification to be too rapid, potentially resulting in "spongy soap" (with internal holes). Too low a temperature will slow saponification and prolong the trace time.

Do not mold until the trace status is reached. Too dilute a soap solution will cause the oil and lye to separate, resulting in oily and unformed finished products. Unlike handmade cold-process soap, industrial soapmaking typically uses a "hot saponification" process, which is more efficient and scalable.

Palm oil (mostly refined palm oil or palm kernel oil) is mixed with other oils and then reacted with sodium hydroxide at high temperatures (80-100°C), resulting in faster and more thorough saponification (usually completed in 1-2 hours).

After the reaction, a "salting-out" step is added: salt is added to separate the soap from the glycerin and water, improving the soap's purity. (Handmade cold-process soap does not undergo salting-out, retaining the glycerin.)

Subsequent steps include alkali refining, bleaching, and molding, resulting in a soap with uniform hardness and a long shelf life, suitable for large-scale sales.