Preservatives for Homemade Soap (Saponification Method)

For homemade bar and liquid soaps made using the saponification method (oil reacting with lye), the soap naturally has a high pH (typically 8-10+). When adding natural ingredients like tofu, cucumber, or aloe vera, which can cause the soap to spoil quickly, using a suitable preservative is necessary.

Based on the properties required for saponified soap, which has a high pH, preservatives that can function effectively in this pH range are needed. Additionally, it's best to add the preservative when the soap has cooled down to a certain temperature, as recommended by the staff.

Two suitable preservatives from our selection that work well in high pH environments and can be added when the soap is cooling are:

• PE 1090 Preservative: This preservative works in a wide pH range of 3-12 and can withstand temperatures up to 80°C during mixing. It is a broad-spectrum preservative effective against bacteria, fungi, and yeast.
• K940 Preservative: This preservative is stable in formulations up to pH 12 and should be mixed in when the temperature is below 80°C. It offers high efficiency against bacteria, yeast, and molds.

Regarding when to add the preservative: As the staff previously advised, it is recommended to add the preservative when the soap is cooling down. For PE 1090 and K940, the mixing temperature should be below 80°C. Adding preservatives at very high temperatures might reduce their effectiveness over time.

Always perform a challenge test on your final product to ensure the preservative is effective for your specific formulation and ingredients.