| What is it? | Euxyl™ k 903 is a liquid natural broad spectrum preservative manufactured by Ashland. It is compatible with non-ionic, anionic, and cationic formulations.
Euxyl™ k 903 is comprised of (source: Formulator Sample Shop):
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| INCI | Benzyl Alcohol (and) Benzoic Acid (and) Dehydroacetic Acid (and) Tocopherol |
| Appearance | Clear yellow liquid |
| Usage rate | 0.4–1.2%; tests from Ashland show it is effective at 0.8–1% |
| Scent | Slight chemically scent with a vague almondy whiff. This scent is soft but noticeable in products that are otherwise unscented. |
| pH | 3.0–4.0 |
| Solubility | Euxyl™ k 903 is approximately 1.2% soluble in water and readily soluble in polar solvents.
From Ashland: “Euxyl™ k 903 preservative is only limitedly soluble in water. 100g of water at 20°C dissolve 1.2g of Euxyl™ k 903 preservative. In polar solvents such as 1,2-propylene glycol, propanol or acetone, Euxyl™ k 903 preservative is readily soluble. In polyalcohols such as glycerol and sorbitol Euxyl™ k 903 preservative is moderately soluble. In aliphates with hydrophilic groups such as 2-octyldecanol and isopropyl myristate, Euxyl™ k 903 preservative is limitedly soluble. In pure aliphatic solvents it is slightly soluble.” |
| Why do we use it in formulations? | Euxyl™ k 903 is a preservative; we include it in our formulations to ensure they don’t grow gross things like mould and fungus. |
| Do you need it? | You should have at least one broad-spectrum preservative; Euxyl™ k 903 is a good choice if you prefer natural preservatives. |
| Refined or unrefined? | Euxyl™ k 903 only exists as a refined product. |
| Strengths | Easy to use broad-spectrum preservative. I find Euxyl™ k 903 doesn’t lower the pH of formulations as much as Geogard® ECT and Geogard Ultra™ do. |
| Weaknesses | It does add a bit of a chemically smell to unscented formulations, and I find it thins emulsions a bit. |
| Alternatives & Substitutions | You’ll need another broad-spectrum preservative. Liquid Germall™ Plus is an effective, versatile choice, but it isn’t natural. Natural alternatives include Geogard Ultra™; and Geogard® ECT. |
| How to Work with It | Include Euxyl™ k 903 in the cool down phase of your formulations. It is somewhat heat stable (Ashland states a maximum temperature of 80°C for no more than 4 hours), but the manufacturer still recommends including it in the cool down phase.
Euxyl™ k 903 works best in a pH range of 3–6, with 5–5.5 being recommended. This preservative is more effective at lower pH ranges. I find it lowers the pH of formulations ~0.75–1.5 pH points, depending on the formulation. This drop can often be enough to take the product into the effective range for the preservative. |
| Storage & Shelf Life | Stored somewhere cool, dark, and dry, Euxyl™ k 903 should last a year. |
| Tips, Tricks, and Quirks | “In formulations as a result of the presence of iron ions, e.g. from mineral thickeners, yellow discolorations were observed.” –Ashland |
| Recommended starter amount | 30mL (1fl oz) |
| Where to Buy it | Buy it from an online DIY ingredient supplier. Mine was a gift from Formulator Sample Shop. |
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