To start off, can you explain a little more about how products like liquid foundation are formulated?

Liquid foundations are formulated like creams (oil and water but with extra properties) as they are designed mainly to deliver a nice lasting mineral pigment film on the face.

In comparison to other creams they contain extra ingredients to suspend and disperse the mineral pigments (they tend to sink at the bottom or cluster together) and to create a nice even film on the skin once applied. Some liquid foundations come with nourishing and active skin ingredients and that is when you would call them BB creams.

With products that are liquid-based, like liquid foundation or liquid lipsticks and liquid eyeshadows, what is the best way to make them last longer?

Liquid foundations and liquid lipsticks are easier to last longer because it is simply a question of applying a fixative (extra layer) on top.

The fixative contains a polymer that creates a transparent and protective film on top of the make-up, so that the pigments stay on the face for longer.

A classic example of a lip fixative is Lipcote & Co Lipcote Lipstick Sealer (£7) which is a liquid naturally based fixative with excellent fixative powers, and for the face NYX Professional Makeup Setting Spray (£7) which is in a spray format.

For the face it is more difficult because it is a more delicate area and personally I would recommend reapplying the product.

A cosmetic chemist’s guide on how to make your make-up last longer