Silicone vs. Water Formulations

Phase Separation

In chemistry, 'like dissolves like'. If you apply a heavy silicone-based foundation (Cyclopentasiloxane as the primary ingredient) over a water-based hydrating primer lacking emulsifiers, the layers will repel each other. This causes the foundation to slide off the primer layer, leading to patches.

How to Read an Ingredient Deck

Don't look at the marketing claims ("hydrating", "poreless"). Look at the first 5 ingredients.

• Water-Based: Aqua/Water is first. Silicone ingredients (ending in -cone, -methicone, -siloxane) are missing or very low on the list.
• Silicone-Based: Aqua might be first (as an emulsion), but the 2nd and 3rd ingredients are typically Cyclopentasiloxane or Dimethicone.
• Oil-Based: Rare in liquid foundations, but common in cream palettes (e.g., RCMA). Primary ingredients will be waxes (Cera Alba), mineral oil, or plant oils.