Glass skin

The look has three physical components and none of them is a product. Light reflects evenly off a surface that is even: skin hydrated enough that the stratum corneum lies flat, free enough of loose dead cells that the surface is not scattering light, and not so oily that the reflection breaks into patches of shine. Everything sold as a glass-skin step is aiming at one of those three.

In practice that means layered lightweight hydration rather than one heavy cream — a hydrating toner or essence pressed in while skin is still damp, a humectant serum, then a moisturiser to hold it in place. Regular gentle exfoliation keeps the surface from going dull. Sunscreen is what makes the result last over months rather than days, because photoaging is what coarsens texture in the first place.

• Hydration rather than oil produces the sheen; a greasy face reads as shine, not glass.
• Pore size, scarring and undertone are structural, and no amount of layering changes them.
• Most viral glass-skin photographs also involve good lighting, a blurring primer and a camera.

Treat it as a description of a finish rather than a destination. The routine underneath — gentle cleansing, layered hydration, mild exfoliation, daily sunscreen — is sound for most people whether or not the result photographs like glass. Skin that is dry, reactive or acne-prone will usually do better setting the aesthetic aside and treating what is actually happening.