PEG-40 Hydrogenated Castor Oil — Frequently Asked Questions

Typically two to five times the weight of the oil being solubilised, though the exact ratio depends on the material. Fragrance oils and essential oils vary widely in how readily they go into clear solution, so a trial is needed rather than a fixed rule. Pre-blending the solubiliser with the oil before adding that mixture to water generally gives better clarity than adding them separately.

Because of micelle size. An emulsifier disperses oil as droplets large enough to scatter visible light, producing opacity. A high-HLB solubiliser such as this forms micelles small enough that they do not scatter light, so the oil is carried in what appears to be a true solution. That is the difference between a cloudy body spray and a clear one.

Yes. It is non-ionic, carrying no charge of its own, so it does not complex with cationic conditioning agents or anionic surfactants the way a charged emulsifier would, and it works across a wide pH range. That tolerance is a large part of why it is the default solubiliser in mixed-charge formulations.

It can do both, and the effect should be assessed rather than assumed. At higher additions it tends to reduce the viscosity of a surfactant system by altering micelle structure, and it can suppress foam. Where a formulation depends on salt-thickened viscosity, adding a solubiliser may require the salt level to be re-optimised.