The Inkey List Polyglutamic Acid Hydrating Serum The Inkey List Polyglutamic Acid Hydrating Serum (£13) works well as a primer as it covers skin with a thin film that locks in moisture and smoothes the surface (but still lets oxygen through). Image Source: cultbeauty.co.uk The Inkey List Polyglutamic Acid Hydrating Serum £13 from cultbeauty.co.uk Buy Now