Interior plastic fading is a symptom of polymer embrittlement. Automotive interiors are subjected to extreme "greenhouse" heat and UV radiation. This causes the essential plasticizers, the oils that keep plastic flexible and dark, to migrate to the surface and evaporate (often seen as a "fog" on the inside of the windshield). Once these oils are gone, the plastic becomes "ashy," brittle, and prone to cracking. Restoration requires a non-greasy, water-based penetrant that re-hydrates the substrate and leaves behind a microscopic UV-absorption layer to halt further degradation.