| What is it? |
Euxyl® K 712 is a natural, water-soluble preservative made by Ashland. Ashland says it has “strong, broad-spectrum efficacy against bacteria, yeasts and molds” and is “fully effective in anionic, cationic and non-ionic systems”. According to the SDS, it is made of:
There are several INCI-identical products available from other manufacturers:
Wherever I was able to check the composition, these products were also ~30% sodium benzoate and ~15% potassium sorbate. |
| INCI |
Sodium Benzoate, Potassium Sorbate, Water |
| Appearance |
“A clear yellowish until brownish liquid with tendency to discolouration. When used in the cosmetic preparation it doesn’t lead to further discolouration as long as the formulation remains acidic.” (Source: Ashland) |
| Usage rate |
0.5–1.5% Assuming 30% sodium benzoate and 15% potassium sorbate, this results in 0.15–0.45% sodium benzoate + 0.075–0.225% potassium sorbate in finished formulations. Some INCI-identical products have slightly different usage rates, so double check with your supplier for what you have. |
| Scent |
“Characteristic” |
| pH |
8–10 (20% solution) |
| Effective pH |
3–5.5 |
| Solubility |
Water soluble |
| Why do we use it in formulations? |
Euxyl® K 712 protects our products from microbial spoilage. |
| Do you need it? |
If you’re looking to get into working with natural preservatives, I think Euxyl® K 712 (or its component ingredients / an INCI-identical option) is a good option to have on hand, but I wouldn’t choose it as your sole preservative. I would not consider it to be super beginner friendly as you need to be able to test and adjust pH, but that’s not a hard skill to learn 🙂 |
| Refined or unrefined? |
This ingredient only exists as a refined product. |
| Strengths |
Fully water soluble natural preservative with a “friendly” INCI. |
| Weaknesses | Performance is very pH reliant.
May not be as effective as synthetic options like Liquid Germall™ Plus; I recommend supporting its performance with strategies like an acidic pH, lowering water activity, and reducing contamination potential. Cosmetic Chemist Phil Geis (author of Cosmetic Microbiology: A Practical Approach) said “Euxyl K712 is not an esp[ecially] effective preservative system and fairly useless at ~ neutral and higher.” on the Chemists Corner forum on June 26, 2021. As always, thorough testing is essential before bringing a product to market. It is possible for sodium benzoate/benzoic acid to break down into benzene when it is combined with L-ascorbic acid. This reaction is exacerbated by UV exposure. This is discussed on page 14 of this CIR document, mostly in the context of canned sodas. “There is some concern that Sodium Benzoate in combination with L-Ascorbic Acid in products can form Benzene, a known human carcinogen. The presence of ascorbic acid and benzoates alone does not lead to the formation of benzene. Certain additional conditions are required for trace levels of benzene to form, including heat, ultraviolet light and metallic ions in the mixture. Therefore, a product containing ascorbic acid and benzoates will not necessarily contain any detectable levels of benzene. The use of EDTA, which chelates metallic ions can therefore be of assistance in the inhibition of benzene formation. Citric Acid is not thought to induce significant benzene production in combination with Benzoic Acid, but some evidence suggests that in the presence of ascorbic acid and benzoic acid, citric acid may accelerate the production of benzene. Therefore, the use of Sodium Benzoate and L-Ascorbic Acid and Citric Acid in the same cosmetic formulations should be avoided.” – Lotion Crafter |
| Alternatives & Substitutions |
Liquid Germall™ Plus is a very easy, though not-natural alternative. It is also fully water soluble and has a broader effective pH range, making it an easy option if you can’t test and adjust pH. Geogard Ultra™ can also be a good option, though it tends to cause downwards pH drift so you’ll need to build an in-situ buffer system to stabilize the pH (instructions are included in the free Humblebee & Me DIY Encyclopedia entry for it). Geogard® ECT and Euxyl™ k 903 can work in emulsions; neither are good choices for fully hydrous formulations due to their benzyl alcohol content. |
| How to Work with It |
Include Euxyl® K 712 in the cool down phase of your formulations. After incorporation, test the pH and lower it to no higher than 5.5 (I recommend 4.5–5 based on my research of potassium sorbate & sodium benzoate). Euxyl® K 712 will raise the pH of formulations, requiring the addition of an acid to lower it to the effective range. Inclusion of a chelator is recommended. “If pH values exceeding 5.5 occur in the production process after the addition of Euxyl® K 712, Euxyl® K 712 is stable but ineffective.” (Souce: Ashland) |
| Storage & Shelf Life |
Stored somewhere cool, dark, and dry, Euxyl® K 712 should last at least 2 years from the date of manufacture. |
| Tips, Tricks, and Quirks |
Euxyl® K 712 is part of the “Euxyl®” line of preservatives from Ashland. There are a lot of products in this line (including Euxyl® PE 9010 and Euxyl™ k 903) and they are all different! The entire name matters. Calling a preservative “Euxyl” is like calling a food “vegetable”—more details are needed. A blend of sodium benzoate and potassium sorbate is a common preservative system in hydrous ingredients like botanical extracts and liquid hydrolyzed proteins. I’ve found several preservatives that are a blend of potassium sorbate & sodium benzoate with a third ingredient to boost performance. Examples include:
The concentration of potassium sorbate & sodium benzoate in these products cannot be assumed to be 30%/15%, but these products may provide some inspiration for ways to boost the performance of Euxyl® K 712. |
| Recommended starter amount |
30g (1.06oz) |
| Where to Buy it |
Buy it from an online DIY ingredient supplier.
I haven’t found Euxyl® K 712 for sale in Canada or the US; instead, I’ve purchased Sodium Benzoate & Potassium Sorbate as individual ingredients. |
Want to learn more about preservatives and compare them? Check out this chart!