|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):
|Benzyl Alcohol (and) Benzoic Acid (and) Dehydroacetic Acid (and) Tocopherol
|Clear yellow liquid
|0.4–1.2%; tests from Ashland show it is effective at 0.8–1%
|Slight chemically scent with a vague almondy whiff. This scent is soft but noticeable in products that are otherwise unscented.
|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.
|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.
|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.