2D Cosmetic Emulsion & Skin Barrier Lab

Emulsion type

Emulsifier HLB

–

Texture

–

O/W: water is the continuous phase, oil is dispersed as droplets. High-HLB (~8–18) emulsifiers curve around the oil, giving a light, spreadable texture.

Test molecule

Molecular weight 150 Da

Polarity (log K_ow) 2.0

Positive log K_ow = lipophilic (oil-loving); negative = hydrophilic (water-loving).

Skin permeability

log K_p (Potts–Guy)

–

K_p (cm/h)

–

log K_p = −2.7 + 0.71·logK_ow − 0.0061·MW (Potts & Guy, 1992). A W/O film is more occlusive and raises skin hydration, boosting effective K_p here by ×1.8.

O/W emulsion

Water phase Oil phase Emulsifier (head/tail) Corneocyte ("brick") Lipid matrix ("mortar") Test molecule